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COPEPOD PARASITES OF FRESH-WATER FISHES
| AND THEIR ECONOMIC RELATIONS TO MUSSEL
ie GLOCHIDIA Ran as a rine By Charles Branch Wilson

“From BULLETIN OF THE BUREAU OF FISHERIES, Volume XXXIV, 1914

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| COPEPOD PARASITES OF FRESH-WATER FISHES
AND THEIR ECONOMIC RELATIONS TO MUSSEL
eEOCHIDIAY = 220: 2:2 > By Charles Branch Wilson

From BULLETIN OF THE BUREAU OF FISHERIES, Volume XXXIV, 1914

CITE FN SNES EN SL OFS NR SNA ost Sets Issued June 28, 1916

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COPEPOD PARASITES OF FRESH-WATER FISHES AND THEIR
ECONOMIC RELATIONS TO MUSSEL GLOCHIDIA

*

By Charles Branch Wilson
State Normal School, Westfield, Massachusetts

&

Contribution from the United States Fisheries Biological Station, Fairport, lowa

33

.

COPEPOD PARASITES: OF FRESH-WATER FISHES AND THEIR
ECONOMIC RELATIONS TO MUSSEL GLOCHIDIA.

&

By CHARLES BRANCH WILSON,
State Normal School, Westfield, Massachusetts.

a

Contribution from the United States Fisheries Biological Station, Fairport, Iowa.
2

w

INTRODUCTION.

Under an appointment by the Commissioner of Fisheries, during the summer of
1914, at the United States Fisheries biological station at Fairport, Iowa, an extended
examination was made of the parasitic copepods which infest our fresh-water fishes in
the Mississippi River and its tributaries and of the mussel glochidia which are also
parasitic upon fish during their term of metamorphosis. Several of the early American
naturalists became interested in the copepods found upon fresh-water fish, and many
new species were described. This was especially true of Le Sueur and Dana, and singu
larly enough the Danish investigator, Krdyer, also obtained a number of American species
from fish sent to the Copenhagen Museum. But in every instance the species described
were isolated, they were sometimes founded upon single specimens, and many of them
have never been seen since their original discovery.

Prof. S. I. Smith published in the Report of the United States Commissioner of Fish
and Fisheries for 1872-73 alist of the crustacean parasites of the fresh-water fishes of
the United States (p. 661-665). This list included two argulids, one caligid, one ergas-
ilid, six lerneopods, three of which were new to science, and two lerneans, 12 species
in all. With true scientific foresight, Prof. Smith stated that the few species he enumer-
ated were ‘‘doubtless only a small fraction of those which really prey upon our common
fishes,” and that his principal object was to ‘‘call attention to the subject and furnish
a basis for future investigation” (p. 661). But his suggestion did not meet with the
response it deserved and beyond the investigations of Smith himself, Packard, Kelli-
cott, Wright, Fasten, and a few others, all widely scattered, no attempt has been made
to increase the list up to the time of the present investigation.

About 1895 Mr. R. R. Gurley, at that time in the employ of the United States
Bureau of Fisheries, gathered together all the available data with reference to the
copepods parasitic upon fresh-water fishes, translating the descriptions given by Krgyer
and other foreign investigators and identifying both hosts and parasites amongst the
material in possession of the Bureau. He made no attempt to establish new species,
but only to bring together all that had been previously described, and he accumulated

333

334 BULLETIN OF THE BUREAU OF FISHERIES.

a manuscript of about 150 pages, which was subsequently turned over to the present
author. ‘This has proved of great value on other occasions as well as the present, and
Gurley’s original identifications and additions to the work of previous authors are
acknowledged in the following pages.

The specimens and other material were derived from several sources. First, the
work of the biological station involves the handling of large numbers of fish, and several
of the regular staff, notably Mr. H. W. Clark, Mr. T. Surber, and Dr. A. D. Howard,
have saved such parasitic copepods as they found while examining the gills for glochidia.
These were generously turned over to the present author, who had also accumulated
a large number of specimens during the surveys of the mussel fauna of various regions
of the United States under the auspices of the Bureau of Fisheries.

These collections were augmented during the present investigations by a careful
examination of all the preserved gills of fish in the possession of the biological station,
of the gills of live fish caught by the regular seining crew or brought to the station for
glochidial infection, and of a large number of dead fish caught by local fishermen.

In these different ways, and including chiefly the waters of the Mississippi Valley,
the original list has been increased to 46 species, 10 of which are new to science; 1 of
Krgyer’s and 1 of Le Sueur’s species have been rediscovered, and there have been added
the larve of 4 other species in various stages of development.

During the investigation it early became apparent that certain economic relations
existed between the copepod parasites and the mussel glochidia, which are also parasitic
on fish. Although the broad fact that parasitized fish do not take or hold glochidia as
well as the nonparasitized ones was observed early in the work at the station, neverthe-
less the existence of particular mutual relations between copepods and glochidia had
never been suspected. Of all the authors above mentioned Fasten is the only one who
has ever treated the copepods from an economic standpoint, and his excellent papers
deal chiefly with the artificial propagation of a single species. It is at once evident,
however, that the interrelations between the fish and the two kinds of parasites must
exert considerable influence upon the artificial propagation of mussels, as well as upon
an intelligent study of the parasitism of the copepods. Accordingly these economical
discussions are placed first in the present paper, and the description of the species is left
until the last.

RELATIONS BETWEEN THE COPEPODS AND THEIR HOSTS.

As has elsewhere been stated, both by the present author (Proceedings of United
States National Museum, vol. 25, p. 654) and by other investigators, it is not probable
that the copepod parasites of fresh-water fishes become under natural conditions a
serious menace to the life of their host. But it must be remembered that their presence
upon the fish is always injurious to the latter and can never be beneficial nor even
indifferent.

1. There is a notion prevalent in certain quarters that a limited amount of dirt and
vermin is wholesome rather than harmful. It is needless to say that this is erroneous,
and that there is no truth also in the idea that a few of these creatures do their host
no real harm, but that a considerable number must be present in order to become really
injurious. Even a single parasite withdraws from its host enough blood for its own

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 335

sustenance. That amount may be small, but it is nevertheless a loss, and it weakens
the fish’s vitality by just so much. The simple fact that a sufficient number of para-
sites can weaken or even kill a fish is enough to prove that each one does his share toward
that end and is therefore harmful. And here in the Mississippi Valley there are other
considerations which tend to greatly increase this influence of parasitism.

2. The parasites, especially the ergasilids, are more numerous upon young fish;
one can scarcely examine a young crappie or calico bass 3 to 5 inches in length without
finding it infested with Eygasilus ceruleus, its particular parasite, and the same may be
said of the hosts of the other ergasilids. It is not quite as noticeable in the case of the
argulids and lernzopods, although even here the smaller fish are the ones most frequently
infested. ‘These young fish are like the young of all animals, including even man. They
are growing rapidly; they need all the vital energy they can produce to carry on this
growth successfully, and hence they are more susceptible to the injurious effects of
parasitism than the matured adult. We thus find a maximum of numbers of parasites
at that very stage of development when there is a minimum of resistance on the part of
the host, and this greatly increases the influence of the former upon the latter.

3. Again, the parasites are more numerous in the slews and cut-offs (so-called lakes)
than in the main river. This is due partly to the absence of a current, thereby enabling
the parasite larva to swim about freely, and partly to the crowding together of the para-
sites and fish, which materially aids the former in their search for the latter; but in
these shut-off bodies of water the conditions are not as favorable to the fish as in the
open river, especially late in the season. There is not.as much food, the water is not
as well aerated, and there is a keener struggle for existence. Furthermore, in these
slews the young fish far outnumber the older ones; these are the very places to which
they resort to escape their enemies. Scarcely a fish can be found in these ‘‘lakes” and
slews which is free from parasites, and towing reveals the presence of large numbers of
parasite larvae swimming about in search of a host. Thus the parasites attack their hosts
not only at the stage of development when they are most susceptible, but also in the
places and under the conditions when they are least able to withstand the attack, again
greatly augmenting the influence of parasitism.

4. With the time, the place, and the conditions thus favorable to the parasites,
the latter respond quickly and show an abnormal increase in development. A far greater
number reach maturity than under less favorable conditions; these in turn breed, and
the number of larve is increased a hundredfold; a considerable percentage find hosts,
thus crowding the gills of the young and already weakened fish. In this way parasites
that are comparatively harmless under ordinary conditions may, and often do, become
a serious menace to the life of the fish.

These considerations are enough to show that the presence of even a few parasites
is not a matter of indifference. Fortunately, under ordinary conditions the parasite
has an even harder struggle for existence than its host. In this struggle the different
kinds of parasites are affected differently, while the ultimate issue is the same for them all.

The ergasilids swim about freely until they reach maturity. The male never be-
comes a parasite, but completes its life as a free swimmer, while the female seeks a par-
ticular host. During this comparatively long free-swimming period both sexes have to

336 BULLETIN OF THE BUREAU OF FISHERIES.

contend with many enemies. They are then a part of the plankton and as such have to
contribute their share toward the support of all the varied life which feeds upon the
plankton. There are many animals which eat copepods and none of them are at all
particular as to the species. These free-swimming ergasilids are fully as toothsome as
other kinds and are as often eaten. The male never escapes this danger, but the female
does when she has once fastened to the gills of a fish. It sometimes happens, however,
that when the female is ready to fasten to a fish all the fishes suitable for hosts have left
the vicinity. Under such conditions the female parasite must die unless she can swim
far enough to find a host.

The argulids swim about freely, even after reaching maturity, especially the males.
During this swimming they also become part of the plankton and share in its dangers
and vicissitudes. Being external parasites, they are not compelled to find a particular
host, for they can remain temporarily upon almost any fish until their true host is found.
They are thus much less susceptible to the dangers of the plankton than the ergasilids,
and when they have once reached maturity they are thenceforth free from such dangers.
Their much larger size also operates in their favor, for they are too bulky to be caught
by most of the creatures which eat ordinary copepods.

The lerneopods have but a very short free-swimming period, a few hours at the
most, and during that time they, too, are subject to the dangers of the plankton. They
must not only survive these dangers but they must also find a particular host within
this brief period or they perish; and the same disaster often overtakes them that
happens to the ergasilids, namely, when they are ready to attach themselves there are
no suitable hosts available.

The lernzids also become a part of the free-swimming plankton at two separate
periods in their development. First during the nauplius and metanauplius stages,
when they are indistinguishable from all other copepods in the same stages, so far as the
dangers of the plankton are concerned. Then they spend the copepodid stages as
parasites upon the gills of some fish, apparently any that happens to be available. On
leaving this intermediate host they again enter the plankton and swim about freely
while a union of the sexes takes place. The male develops no farther, but the female
must seek a permanent host, and this time it must be a particular species of fish.
During this latter period, therefore, they are in the same condition as the lerneopods
and often experience the same trouble, namely, when they are fully developed there
are no suitable hosts available.

It follows that the parasites are ordinarily held in check by these means, and if
they are to become anything of a menace to the fish there must be peculiar conditions
favorable to them and unfavorable to their hosts. The custom practiced by the bio-
logical station of seining the fish out of the ‘‘lakes’’ and slews that are likely to go dry
and putting them back into the main river is the best thing that could be done to get
rid of the parasites. We have just seen that the latter breed rapidly under the conditions
obtaining in the slew and that everything works together in their favor. By removing
the fish such breeding is at once stopped; all the parasite larvee and adults left in the
slew die, and the new conditions in the main river are such as to keep subsequent breed-
ing within due bounds.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 337
RELATIONS BETWEEN THE COPEPODS AND THE GLOCHIDIA.

We have just discussed the relations between the fish and the copepods, but both
copepods and glochidia infest our common fresh-water fishes. Consequently, in view
of the efforts which are being put forth by the United States Bureau of Fisheries for the
success of artificial mussel propagation it becomes imperative to know whether the
habits of these two kinds of parasites are harmonious or antagonistic. Does the presence
of copepods upon our common fishes influence in any way their susceptibility to infection
by mussel glochidia? This problem can be most intelligently discussed in the form of
a series of questions and answers.

I. Are the fish that serve as hosts for the copepods those which ave naturally susceptible
to infection by glochidia?

This question can be best answered by arranging in tabular form a list of the fishes
with their glochidia and copepod parasites in parallel columns.

BULLETIN OF THE BUREAU OF FISHERIES.

338

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COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES.

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BULLETIN OF THE BUREAU OF FISHERIES.

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‘ponunuoj—sSaLISVUVd GOdydOD ANV VIGIHOOTD YAH], HLIM SLSOP HSI

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 341

A careful reading of this table shows us:

1. The fish which carry the copepods are also those which serve as hosts for the
glochidia.

There are a few exceptions on either side—some fish, like the eel and the shovel-
nosed sturgeon, which carry only glochidia,.and others, like the dogfish and the bull-
head, which carry only copepods. But these are simply the exceptions that prove the
rule, and we must also remember that not all the fishes in the list have been thoroughly
examined for both copepods and glochidia. Future investigations are very likely to
reduce these exceptions and possibly to eliminate them entirely. This is exactly what
would be expected, for the temporary parasite, the glochidium, is not so very different
in some respects from the permanent parasite, the copepod. The conditions which are
favorable to the one would favor the other also, and the conditions which are adverse to
the one would be adverse to the other. Hence we may go a step further and affirm:

2. The species of fish which are ordinarily free from copepod parasites do not furnish
conditions favorable to infection by glochidia.

The numerous species of buffalofish, carp, suckers, lampreys, minnows, shiners,
dace, chubs, and darters are excellent examples. The above table includes all the fresh-
water fish at present known to serve as hosts for either copepods or glochidia, and prac-
tically none of these fish appear in either list. Nor are they likely to appear in any
numbers, for these fish have been as thoroughly examined as any others, but nothing
has been found upon them. Lefevre and Curtis mention some of the mechanical factors
which tend to render a fish immune to infection by glochidia, such as the smallness of
the gill openings, the rapidity of the fin movements, and the texture of the gills. They
mention as the most striking instances of immunity the German carp, certain minnows,
and the darters, three of the above-named fish. By means of artificial infection they
exposed these fish to glochidia, a few of which fastened upon their gills and fins; but
these were quickly sloughed off, and none could be carried through the parasitic period.
“The disappearance of the hookless glochidia of Lampsilis from both gills and fins of
thecarp * * * suggests rather that there may be some reaction of the host’s tissues
comparable to the processes which confer immunity against parasitic bacteria in higher
vertebrates.’”’ (Lefevre and Curtis, Bulletin Bureau of Fisheries, vol. xxx, p. 163.)

We can readily understand how an immunity of this character could operate against
the parasitic copepods as well as against the glochidia. Extensive examination in the
future may, and probably will, reveal straggling copepods and glochidia, but in such
small numbers that they must be regarded as accidental infections. ¢

3. The fish which make the best copepod hosts are also those which are naturally
infected with the greatest number and variety of glochidia.

A fish’s efficiency as a host may be measured either by the number of any single
parasite it harbors, or by the variety of species. In the copepod parasites these two
criteria are usually separated and must be considered independently. In the mussel
glochidia they are nearly always united, and may therefore be treated conjointly.

Keeping these facts in view, we notice first that the crappie, Pomoxis annularis,
stands at the head of both lists. It serves as the host of at least 13 species of mussel
glochidia, and yields often as many as 500 or 800 specimens of some parttcular species

@ Argulus foliaceus and Ergasilus sieboldii have been found once or twice on the carp (Cyprinus carpio) in Europe, while
Lerneocera pectoralis was reported by Kellicott from the red-fin shiner (Notropis cornutus) in the Shiawassee River, Mich.

342 BULLETIN OF THE BUREAU OF FISHERIES.

like L. ligamentina or L. ventricosa. When artificially infected, each crappie will take
from 1,000 to 2,000 glochidia and sometimes even more.

Turning now to the copepods, we find that while it carries on its gills only twospecies,
it is, nevertheless, the worst infected fish in the Mississippi River so far as numbers are
concerned. Hardly a crappie examined during the summer season failed to yield speci-
mens of one or both copepods, and frequently the number from a single fish reached into
the hundreds and sometimes came close to a thousand. The difference in size between
the glochidia and copepods make these numbers closely correspond, and the limit in
both instances is apparently determined only by the actual living space on the gills.

The second fish on the list is the sheepshead, A plodinotus grunniens, which serves as
a host for 11 species of mussels, and upon the gills of which the number of individual
glochidia is usually well up in the hundreds and frequently reaches into the thousands. @
This is an apparent exception to the rule, for while there is an external Arvgulus parasite
to correspond with the few fin glochidia, a careful examination of all the sheeps-
head gills that were available (about 500) failed to reveal a single copepod; but there
are certain facts which profoundly influence our judgment in the present instance.

First, and of the greatest importance, this fish habitually feeds upon thin-shelled
mussels, crushing the shells with its powerful pharyngeal jaws. Whenever the shell of a
gravid mussel is crushed in this way the gills of the fish necessarily become infected with
the glochidia which are set free. L. /evissima and P. donaciformis are the ones whose
glochidia are found in greatest numbers, and these as well as most of the others have
papery shells. This method of infection is quite different from that in the crappie and
other fish and comes close to being artificial. Furthermore, such infection is practically
constant, in fact as constant as the feeding of the fish, and thus the gills are kept loaded
with glochidia all the time. The presence of these glochidia prohibits that of the cope-
pods, as will be shown later. The glochidia of the thick-shelled mussels like Q. heros
are obtained in the usual way and are much fewer in number.

Again we find upon the sheepshead’s gills, in addition to the mussel glochidia a
trematode ectoparasite, which exists in as great abundance as the copepods upon the
gills of the crappie. The presence of these worms may still further explain the absence
of copepods.

After the sheepshead comes the sauger with six species of glochidia, the green sun-
fish with five, the bluegill and white bass with four each, and the gizzard shad, the large-
mouth black bass, the skipjack, and the calico bass with three each. Of these the
bluegill, the white bass, and the calico bass are each infested with the same two species
of Ergasilus as the crappie, in smaller numbers but still to a considerable degree. The
largemouth black bass carries a still smaller number of individual copepods but com-
pensates for it by being the host of five different species. The green sunfish, the gizzard
shad, and the skipjack have but a single copepod parasite on their gills, but they are
also really the host of but a single kind of glochidium, the others being found in such
small numbers that they can be regarded only as accidental infections. Having thus
determined that the same fish serve as hosts for both copepods and glochidia, a second
question naturally arises:

@ On the gills of one fish of this species 5,200 glochidia of P. donaciformis were found, and upon another fish 10,400 of the same
glochidia.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 343

II. Is there any fellowship between the different species of the two kinds of parasites?
Do we find certain species of glochidia associated with the same copepod im a majority of
instances?

This question can also be answered by reference to the table (p. 338), from which
we deduce the following:

1. Of the external-fin glochidia Anodonta corpulenta is by far the most widely dis-
tributed and is always accompanied by an external Argulus parasite, usually A. appen-
diculosus. The green sunfish, the calico bass, and the skipjack are apparent exceptions;
Anodonta glochidia have been found upon them but no Argulus copepod. It must be
remembered, however, that the glochidia are fastened in the fins and remain there no
matter how long the fish may have been kept or how much it may have been handled.
On the other hand, the copepod merely clings to the outside surface of the fish and is
easily brushed off when alive and practically always falls off when dead. Only a few
of these fish have been examined under conditions favorable for finding the copepods,
while the conditions are always favorable for finding glochidia.

Such being the case, it seems reasonable to expect that an Argulus parasite will
be found upon the three fish just mentioned as the result of future examination; but
the argument ought to work equally well in the opposite direction, and hence we may
look for the future discovery of the glochidia of A. corpulenta upon the channel cat, its
copepod fellow having been already found.

2. The glochidia found upon the gills of fish may be divided into the two great
groups of Lampsilis species and Quadrula species. Accompanying the former we find
Ergasilus ceruleus in every instance, except upon the largemouth black bass, where it
is replaced by Ergastlus nigritus, one of the new species. Accompanying the Quadrulas
we find Ergastlus versicolor upon the catfishes and the skipjack and Ergasilus centrarchi-
darum upon the Centrarchide. In this instance the copepods and glochidia are equally
well protected, and the only hindrance to their discovery is the lack of fish specimens.
Some species of fish are always scarce, while others that may be ordinarily plentiful
may be scarce at just the time when they are likely to become infested with the copepods
or the glochidia. Hence, while one of the parasites might be well known upon the fish,
the other might have escaped notice.

Apparently something of this sort has happened to a few of the catfishes and Cen-
trarchide; copepods have been found upon them repeatedly, but thus far no mussel
glochidia have been discovered. It would seem reasonable, however, to expect them,
and some species of Quadrula will probably be found in the future upon the yellow cat,
the bullhead, and the Fulton cat, while some species of Lampsilis will be found upon

the common sunfish, Ewpomotis gibbosus, the warmouth bass, and the smallmouth black
bass.?

In connection with the association between FE. centrarchidarum and Quadrula
glochidia the following may be suggested:

(a) E. centrarchidarum is found on the gills of the largemouth black bass, but it is
accompanied by F. nigritus, one of the new species which evidently takes the place on
this host of E. ceruleus, the regular associate of Lampsilis species. The presence of
centrarchidarum, therefore, is not to be interpreted as indicating that it is here excep-

@ Since the writing of this paper two species of Lampsilis glochidia have been discovered upon the gills of the warmouth
bass and have been inserted in the table on page 338.

16825°—16 2

344 BULLETIN OF THE BUREAU OF FISHERIES.

tionally associated with Lampsilis species but, rather, that Quadrula glochidia will be
found in the future upon this fish as they have been upon so many of the sunfishes and
basses other than the largemouth.

(b) Upon the sunfishes it is worth noticing that the two copepods ceruleus and
centrarchidarum occur together, and we should expect such fish to become the natural
hosts of both Lampsilis and Quadrula glochidia. Two of them, the bluegill and the
green sunfish, have already yielded both kinds of glochidia, and it would seem probable
that future investigation will find both kinds upon the other sunfish where now there
is but a single kind.

(c) E. centrarchidarum is found upon the gills of the wall-eye, which have thus far
yielded only Lampsilis glochidia; but upon the sauger, another fish of the same genus
as the wall-eye, both kinds of copepods and both kinds of glochidia appear. Further-
more, both fishes yield the same species of Argulus, so that it does not seem presumptive
to suppose that the second species of Ergasilus and Quadrula glochidia will eventually
be found upon the wall-eye, as they have already been upon the sauger.

3. There is a single well-marked instance of individual association between a
glochidium and a copepod. Lampsilis anodontoides, whose glochidia are practically con-
fined to the gars, is found to be accompanied by a peculiar copepod, Evgasilus elegans,
another new species, which differs markedly from the others of its genus in the fact
that the female remains free swimming for a much longer period. Indeed, it seems
probable that they leave the fish’s gills after having fastened to them and swim about
freely. There are two other new species, Ergasilus lanceolatus from the gizzard shad
and E. elongatus from the spoonbill cat, which are fully as peculiar as EF. elegans and
which may well be the copepod half of other individual associations whose glochidial half
has not yet appeared. Furthermore, we may look for FE. elegans upon the alligator gar,
whose gills have already yielded specimens of Lampstlts anodontoides.

4. It has long been known that certain species of copepods are confined to particular
hosts and are not found upon any others. The table furnishes us several well-marked
examples of this: Argulus mississtppiensis and A. ingens are each found upon a single
host, and although the two hosts are gars and very closely related to each other the
copepods are distinct species. Again, the two species of Ergasilus just mentioned,
namely, /anceolatus and elongatus, are each restricted to a single kind of fish and are not
likely to be found elsewhere. The same is true of Ergasitlus megaceros and of Salmincola
oquassa and S. edwards; in fact, a good proportion of copepod parasites of both fresh-
water and salt-water fish show such restrictions.

When we look at the glochidia we find that there are fully as many of them confined
to a single host. Lampsilis alata, gracilis, and purpurata, and Quadrula solida, ebenus,
and frigona are good examples. Probably further investigations will modify many of
these as well as of the copepods, but it is equally probable that some of them will prove
to be always solitary. In the case of the glochidia we are not compelled to wait for
natural infections, for we can subject a fish to the glochidia of many mussels and deter-
mine experimentally whether or not it will make a suitable host for them. In fact,
this has been done by Dr. A. D. Howard, who, in the Bureau of Fisheries document
no. 801, calls attention on page 36 to what he calls ‘‘Restricted infection,’ which

he has demonstrated by actual experiment in the case of Quadrula pustulosa upon the
channel cat.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 345

Nothing of this sort can be tried with the copepods, since we can not supply larve
in the right stages of development as we can glochidia. But although our knowledge of
both kinds of parasites is rather limited as yet, enough data have been accumulated to
show that the two kinds of parasites behave very similarly in regard to their hosts.
There is thus a decided similarity between them when each is found by itself upon some
suitable host.

III. Does the actual presence of copepods on a fish’s gills exert any influence upon its
susceptibility to infection by-glochidia?

In other words, granting that the same fish do serve as hosts for both glochidia and
copepods, are the conditions favorable for both at the same time? ‘This is manifestly
something which can not be watched under natural conditions, and the only way to
answer the question is by artificial infection experiments. Accordingly a hundred crap-
pies, Pomoxis annularis, of nearly uniform size (5 to 6 inches long), which had been
caught and brought to the station for artificial infection, were carefully examined and
25 were found to be infested with Ergasilus ceruleus, while the other 75 were free from
them. The entire hundred were then infected in the usual manner and under exactly
the same conditions with the glochidia of the black sand-shell, Lampsilis recta. After
infection the 25 parasitized fish were killed, their gills were removed, and the number
of copepods and glochidia on each was counted with the following results:

Fish. Glochidia. | Copepods. Fish. Glochidia. | Copepods.
1 ° 350 14 102 87
2 46 Iso 15 7 393
3 176 I2r 16 190 36
4 126 140 TT, 63 310
5 104 78 18 495 8
6 337 7 19 4° 196
7 47 253 20 80 112
8 38 218 21 16 372
9 169 142 22 395 Io

10 257 44 23 9 403
1I 301 63 24 II 396
12 372 30 25 143 134
13 280 31

The average number of glochidia upon each of the nonparasitized fish was between
1,000 and 1,200. By comparing this with the numbers given in the table we deduce the
following:

1. The presence of even a small number of copepods upon the gills of a fish reduces
its susceptibility to infection by glochidia to one-third or one-fourth of what it would
be if no copepods were present.

Even the gills that contained 10 copepods or less showed the presence of only a
few hundred glochidia instead of the thousand or more upon a nonparasitized fish.
Such a marked reduction can not be explained by the mere presence of the copepods;
they do not occupy enough of the gills to exert any crowding influence, neither are they
ever found attached to the tips of the filaments where the glochidia mostly congregate.
Manifestly there is room enough for both kinds of parasites without serious crowding;
gills that will accommodate 1,200 glochidia with no apparent injury to the fish can
certainly find room for more than 400 when only 10 copepods are present.

Lefevre and Curtis say that the stimulus which causes the glochidium to close and
thus to fasten itself to the fish is purely a mechanical one (Bulletin Bureau of Fisheries,

346 BULLETIN OF THE BUREAU OF FISHERIES.

vol. XXvll, pt. 1, p. 622). Here again the mere presence of a few copepods upon the
gills of a fish could have no effect upon such a stimulus. The respiratory movements of
the fish may have considerable to do with it; the crappie’s respiration is not very vigor-
ous even at its best, and this is especially true of small fish (Lefevre Bea Curtis, Journal
Experimental Zoology, vol. 9, p. 103).

The irritation due to the presence of parasitic copepods may still further reduce
these movements and thus prevent infection by glochidia; but if this were the only cause
10 copepods could hardly produce so large an effect. It would seem as if there must be
something further, either chemical or physiological in its action, in order to accomplish
the known results. It will not be very easy to prove what this is, but meanwhile the
facts remain unaltered that in some way the presence of a very few copepods greatly
reduces the fish’s susceptibility to infection by glochidia.

2. As the number of copepods upon a fish’s gills increases its susceptibility to
infection by glochidia diminishes. Naturally a limit is soon reached beyond which the
susceptibility has diminished so much that practically there can be no infection at all;
this limit for small crappies is about 200 copepods. If more than this number is present,
the glochidia are very scattering and are usually below 50 in number. The copepods
often increase to 500, and in such instances there are no glochidia, or, if any, their —
number is expressed by a single digit.

Certain conclusions naturally follow from these facts. The first is that it is obvi-
ously disadvantageous to attempt to infect with glochidia fish that are already carrying
copepods. A few glochidia will always stick to their gills, but not in sufficient numbers
to repay the labor expended. Since the large fish are relatively freer from copepods
than the smaller ones, it follows that they make the better hosts. Not only are their
gills larger and thus capable of carrying more glochidia, but the latter will fasten to
them more readily because of the comparative absence of copepods.

Again, the fish from the main river, whatever their size, make better hosts than those
from the slews and “‘lakes,’’ because they, too, are freer from copepods. ‘This is espe-
cially true at those times when the water is very low; during a long-continued drought
it would be of little use to try infecting fish caught in such places because they would
be so infested with other parasites that very few of the glochidia would fasten to them.
The best thing to do with such fish would be to replace them in the main river and trust
to taking them again after they had gotten rid of their copepods.

3. It is obviously a poor rule that does not work both ways, and we find that the
presence of glochidia is as prohibitive to the copepods as are the latter to the former.
This also is something that can not be watched under natural conditions; neither can
it be proved by experiment, for we can not supply parasitic copepods as freely as we can
glochidia; but it is abundantly sustained by a study of natural infections on the gills of
fish taken in the river. There are in the possession of the biological station about 1,000
vials of gills showing natural infection by various glochidia. These were all carefully
examined for parasitic copepods under a dissecting microscope, and in not a single
instance where the number of glochidia exceeded 300 was there even a single copepod
present.

This mutual antagonism between the copepods and glochidia enables us to under-
stand clearly why the sheepshead’s gills are never infested with copepods. From the
nature of the fish’s food, as already explained, its gills are kept crowded with glochidia

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 347

all the time, and thus the copepods are shut out. This leads to the conclusion that when
a fish’s gills are artificially infected with glochidia the fish is thereby rendered immune
to the copepods. Artificial infection therefore, as regularly practiced at the biological
station, not only does the fish no harm but is even positively beneficial.

And this suggests a possible safeguard or remedy for some fish hatcheries. It occa-
sionally happens that parasitic copepods get to breeding in a hatchery in such numbers
that they kill the fish. Judging from the cases thus far reported, this seems more
likely to occur among trout than among other game fish. The European trout (Salmo
jario Linneeus) is the natural host of Margaritana margaritijera, but our American trout
have been examined very little for glochidia. However, if there is any virtue in the
conclusions here drawn, the very fact that they are more susceptible than other fish to
the copepod parasites indicates that they would make excellent hosts for glochidia.
If this be so, an infection with glochidia would be harmless to the fish, but at the same
time would render them immune to the copepods. At all events, the experiment is
worth trying.

4. The breeding season of the copepods thus acquires especial economic importance
with reference to mussel propagation. It is manifest that at the close of a breeding
season, when the larval brood of copepods have sought and found their hosts, their
numbers will be at a maximum. Consequently this would be the time least favorable
to infection with glochidia. On the other hand, the early spring, before the copepods
begin to breed, and the intervals between successive breeding periods, would be the
most favorable to glochidial infection.

We are not yet sufficiently acquainted with either kind of parasite to be able to
make a complete schedule of their times of breeding, but many interesting facts have
been ascertained.

Lefevre and Curtis in the Bulletin of the Bureau of Fisheries, volume xxx, page 141,
divide mussels into two groups according to the length of the periad of gravidity. Those
having a long period of gravidity, among which Lampsilis species predominate, produce
ripe glochidia during the fall and winter and spring months. Those having a short
period of gravidity, among which Quadrula species predominate, produce ripe glochidia
during the summer months. Turning now to the copepods, we find that the ergasilids
and argulids have three breeding seasons in the year, the first at the end of May or the
beginning of June, the second at the middle or latter part of July, and the third in the
latter part of September. We do not yet know all the breeding seasons of the lernzeids
and lerneeopods, but from the material here presented and that obtained from many other
investigations it is certain that they also have a breeding season during the middle or
latter part of July, and it is probable that there are two other seasons corresponding to
those just given.

Comparing the breeding of the copepods with that of the mussels, it will be seen
that the winter or early spring is the best time for infection with Lampsilis glochidia,
since the only copepods then on the fish’s gills are such adults as have lasted through
the winter. None of the Quadrula group produce glochidia early enough to be used
for spring infection, and the best months for them would be July and September, just
before the second and third copepod breeding seasons; and from what has already been
said of the cumulative effects of unfavorable conditions during low water the month of
July would ordinarily be preferable to September.

348 BULLETIN OF THE BUREAU OF FISHERIES. .

In the paper already referred to Lefevre and Curtis call attention to the desirability
of reducing the length of the parasitic period of the glochidium (p. 191), which is inversely
proportional to the temperature of the water. Whether the shortening of the parasitic
period during the warm summer weather will compensate for the increase in the num-
ber of parasitic copepods is a question that can be decided only after careful experi-
mentation. We now know, however, that the presence of these copepods and their
periods of breeding are factors that must be given due consideration before the question

can be solved.
SYSTEMATIC,

A complete description, fully illustrated with appropriate figures, is given of all the
species which are new to science. Of those which have been previously described only
such notes are included as are of interest or furnish additional information. The larve
of a few species were hatched out in the laboratory of the station, and they also are
fully described and illustrated, since they add considerably to our previous knowledge
of the species. Several parasites were obtained by H. Krdéyer, a Danish zoologist, from
fish taken near New Orleans and sent to the Royal Museumin Copenhagen. Most of these
fish were such as come up the Mississippi River from the Gulf of Mexico, and hence their
parasites can not be included amongst the strictly fresh-water species; but they are
included in the present list because they are likely to be found in that part of the river.

The parasites of fish in the Great Lakes, the Lake of the Woods in Canada, and of
several isolated lakes are also enumerated, since they are all fresh-water forms and really
belong with the great fresh-water fauna of the interior of our continent. A few species
have been included from west of the Rocky Mountains and east of the Appalachians.

THE ARGULIDE.

Argulus canadensis, new species. (Pl. Lx.)

Host and record of specimens.—Three fine females were obtained by T. Surber at Le Claire, Minn.,
from fish caught in the Lake of the Woods. ‘Two were from a species of whitefish, Coregonus, while the
third was from a rock sturgeon, Acipenser rubicundus. ‘The better of the first two is made the type of
the new species and has been given catalogue no. 43521, U. S. National Museum. ‘The other has been
given catalogue no. 43525, U. S. National Museum, while the specimen from the sturgeon received
catalogue no. 43526, U. S. National Museum.

Specific characters of the female.—Carapace elliptical, a little longer than wide, the posterior lobes
broad, evenly rounded, and reaching to about the center of the third thorax segment, leaving the two
posterior pairs of legs fully visible in dorsal view. Instead of projecting anteriorly the cephalic area is
slightly reentrant, ovate, and relatively very small; posterior sinus one-third the length of the carapace,
its width posteriorly equal to its length, but narrowed and squarely truncated anteriorly. The support-
ing rods in the lateral areas of the carapace are peculiarly arranged, meeting at a point far forward and
giving the creature a sort of hunch-backed appearance. The respiratory areas are also peculiar, the
outer one club-shaped, the large end anterior, while the handle of the club extends backward along the
outer margin of the inner area, an arrangement wholly different from anything heretofore described.
Abdomen a little more than one-fourth the entire length, its width to its length as 5 to 8; anal sinus cut
beyond the center, its sides parallel, lobes narrow-elongate and rather bluntiy rounded, papille basal.
Eyes large and so far forward as to almost touch the anterior margin, but widely separated; sucking disks
also far forward and well separated, one-eighth the width of the carapace.

Antennz small and weakly armed, the terminal joints of the first pair not reaching beyond the
lateral claw, the anterior claw minute and nearly straight; second antenne slender, basal joint enlarged
with a small spine on its posterior margin. A pair of large accessory spines behind the antenne and
close to the median line; another pair between the bases of the maxillipeds or slightly posterior to them.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 349

The supporting rods of the membranous border of the sucking disks are made up of an oblong basal
joint and a series of ro or rr plate-like disks, overlapping one another like shingles and diminishing in
size distally, similar to those in Argulus megalops. ‘The basal joint of the maxillipeds is much swollen,
the basal plate does not quite reach the posterior margin, and is armed with three slender acuminate
teeth; this plate has a rounded lobe outside of the teeth, which carries a short spine at its center. The
ventral protuberance is large in area, oval in outline, and is put on diagonally, the small end filling
out the rounded external lobe just mentioned; there are also spiny areas at the distal end of the basal
and third joints, and over the whole surface of the second joint; there are two terminal claws and a
fingerlike process outside of them.

Color (preserved material), carapace, abdomen, and the entire ventral surface a clear creamy white;
dorsal surface of the thorax covered with rounded spots of a deep reddish purple, with a white streak
through the center above the intestine; these spots extend forward beneath the carapace as far as the
mouth; eyes and semen receptacles a lighter purple.

Total length, 12 mm.; carapace, 7.2 mm. long, 7 mm. wide; abdomen, 3.4 mm. long, 2.2 mm. wide.

(canadensis, Canadian. )

Remarks.—This is a large and powerful parasite and is evidently our American representative of
the European species coregoni. It would be interesting to ascertain whether they produce any such
effect on the fish in the Lake of the Woods as is recorded for the fish of the lakes in Jemtland by Dr.
Nystrom. (Proceedings U. S. National Museum, vol. 25, p. 725.)

That our species is distinct from coregoni is shown by the following differences. There are no
flagella on any of the legs, while in coregoni they are full sized. The cephalic area is reentrant anteriorly
instead of protuberant. The eyes almost touch the anterior margin and are rather small. There is no
ovate papilla on either side of the opening of the oviduct, which Thorell makes one of the prominent
characters of coregont. The respiratory areas are very different, not only from coregoni but from every
other known species of Argulus. This is evidently a northern species, since it has not been found upon
any of the numerous species of Coregonus in the Great Lakes. The male is as yet unknown.

Argulus flavescens, new species. (Pl. Lx1, fig. 7-12.)

Host and record of specimens.—Two females were obtained from the outside of the dogfish, Amia
calva, caught in ‘‘Sunfish Lake,’’ near Fairport, Iowa, August 8, 1914. The betterof the two is made the
type of the new species and has received catalogue no. 47759, U. S. National Museum; the other becomes
a cotype with catalogue no. 47760, U. S. National Museum. A third mutilated specimen was obtained
from the gills of the mud cat, Leptops olivaris.

Specific characters of female.—Carapace elliptical, a little longer than wide, and evenly rounded;
lateral sinuses scarcely perceptible; posterior sinus more than twice as long as wide, and two-fifths the
length of the carapace, with nearly parallel sides; posterior lobes not reaching the abdomen, broad and
plump; abdomen broadly ovate, as wide as long, and narrowed to a short neck where it joins the thorax;
anal sinus about one-third the length of the abdomen, considerably enlarged at the base; anal papille
spherical and basal.

Entire under surface of the body, including the abdomen, covered with small spines, pointing
backwards; eyes small, placed well forward and some distance apart, facets minute; lateral ramifications
of the stomach large and particularly prominent by reason of their color and lobed edges; respiratory
areas made up of a small anterior, nearly circular portion, and a long posterior portion, which reaches
nearly to the tip of the posterior lobes; sucking disks of medium size, placed well forward and close
together. First antenne slender, the anterior claw rudimentary, the lateral claw curved into three-
quarters of a circle, the two terminal joints slender and reaching well beyond the tipof the claw. Second
antenne with swollen basal joint and three long terminal joints, abruptly reduced to one-third the
width of the basal joint and sparsely armed with sete; a small flattened spine on the basal joint of each
antenna and an accessory pair of larger and sharper spines posterior to the second antennz and close to
the midline.

Basal plate of the maxillipeds small and narrow, with short, flattened, and bluntly rounded teeth;
raised area a long and narrow oval; the four terminal joints each with a roughened area along the anterior
and distal margins; last joint tipped with two minute claws and a fingerlike process. Swimming legs of
the usual pattern, the posterior pair with a small lobe, which is not boot-shaped, but flares at both ends,

350 BULLETIN OF THE BUREAU OF FISHERIES.

and which does not reach the margin of the abdomen. The supporting rods of the border of the sucking
disks are made up of a basal rectangular section and from four to six barrel-shaped terminal sections,
the distal one incomplete and shaped like the letter J, with the stem convoluted.

Color, a pale yellowish white; the entire digestive canal, including the ramifications of the stomach,
a rich creamy yellow, in strong contrast to the white background; eyes dark cinnamon brown; upper
surface of the body covered with irregular spots of jet black, thickly sprinkled along the center and over
the lateral ramifications of the stomach, but entirely lacking around the eyes and the anterolateral
sinuses; semen receptacles yellow, surrounded by a black line.

Total length, 6 mm.; carapace, 4.35 mm. long, 4.20 mm. wide; abdomen 1 mm. long and wide.

(flavescens, yellowish, alluding to the digestive system).

Remarks.—This is a small and highly colored species and is apparently rather rare, since only the
three specimens were found during the entire summer. It may be recognized at once by the prominent
yellow lateral lobes of the stomach, the jet-black pigment spots on the dorsal surface, and the compara-
tively minute abdomen, with its tiny anal papille in the enlarged base of the anal sinus. It seems
probable that the mud cat is the real host of this species and that the two specimens on the outside of
the dogfish were only seeking temporary lodgment.

Argulus mississippiensis, new species. (Pl. Lx1, fig. 13-15; pl. uxn, fig. 21; pl. LXmI.)

Host and record of specimens.—Six males and six females were taken by the author from the short-
nosed gar, Lepisosteus platostomus, at Fairport, Iowa, July 17,1912. They have been given catalogue no.
43571, U. S. National Museum. One of the largest females has been selected as the type of the species
and has received catalogue no. 43528, U. S. National Museum. ‘This species is found upon the back of
the gar’s neck just above the dorsal aorta, and there is usually only one parasite on each fish.

Specific characters of female.—Carapace about three-fifths of an ellipse, its long diameter transverse;
anterior sinuses narrow and deep; posterior sinuses one-quarter the length of the carapace, longer than
wide, its sides approximately parallel; lateral lobes very broad, obliquely truncated posteriorly, not
quite reaching the abdomen. Eyes comparatively minute and widely separated; respiratory areas
placed obliquely at the extreme posterior end of each lobe, the outer area semilunar, its ends consid-
erably enlarged and well rounded, the inner area about the same size as one of the sucking disks, inserted
on the inner side of the outer area near its anterior end, but separated from it by a considerable interval.
Abdomen elliptical, one-fourth longer than wide, and half as long as the carapace; posterior sinus narrow-
triangular, not cut to the center; papille lateral, near the tips of the lobes; semen receptacles elliptical
and close to the midline, their long diameters parallel with the axis of the abdomen.

Antennz small and stout; first pair with a medium-sized anterior claw and a long and stout lateral
one, the terminal joints linear and not projecting beyond the tip of the lateral claw; second pair with a
ventral protuberance on the basal joint just above the basal spine. Sucking disks small, only one-
fourteenth the width of the carapace and widely separated; supporting rods slender and made up of a vari-
able number of linear joints; no fringe on the margin. Maxillipeds also small but stout; basal plate
projecting far behind the margin of the basal joint and carrying a large lobe distal to the spines; the latter
large and acuminate; ventral protuberance small and circular; a roughened plate on the third joint;
terminal claws and papilla minute. A pair of small accessory spines between the bases of these maxilli-
peds and another larger pair some distance behind the antenne.

Each of the three posterior pairs of swimming legs carries a ventral lobe fringed with sete on the
basal joint; the lobes on the second and third legs are small, that on the fourth legs is much larger and
projects beyond the lateral margin of the abdomen; the second joint of the endopod of the fourth legs
also carries a small posterior lobe. There is a small anal papilla on either side of the opening of the
oviduct.

Total length of figured specimen, 15 mm.; carapace, 10 mm. long, 12 mm. wide; abdomen, 4.80
mm. long, 3.75 mm. wide.

Specific characters of male.-—The general make-up of the male is similar to that of the female, the
carapace lobes slightly overlapping the base of the abdomen; the testes are elliptical and not much
larger than the semen receptacles in the female; the basal portion of the anal sinus, proximal to the
papille, is a mere slit, whose sides are in contact or even overlap slightly. The secondary sexual appa-
ratus is very complicated and closely resembles that of A. lepidostei. There isa roughened plate, armed

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 351

with short spines, on the ventral surface of the basal joint of the second legs, at each end of which is a
stiff fingerlike projection; the basal joint of the third legs carries a boot-shaped posterior lobe fringed
with sete; on the anterior margin, parallel with the axis of the joint, is a fingerlike process, covered with
short spines, whose tip is turned forward just beyond the distal end of the joint; inside of this tip is
the base of another long process, flattened anteroposteriorly and covered with short spines, which extends
outward parallel with the second joint and overlaps the bases of the rami; on the posterior margin of
this second joint, distal to the opening of the semen receptacle, is a small laminate process, fringed with
long sete; the musculature of these two basal joints is peculiar, as may be seen in fig. 27. The peg on
the fourth leg is double and stouter than in most species.

Total length of figured specimen, 11 mm.; carapace, 7.50 mm. long, 9 mm. wide; abdomen, 3.50
mm. long, 2.50 mm. wide.

Color of both sexes: Carapace, abdomen, and the ventral surface a light yellow, thickly sprinkled
on the dorsal surface with small circular dots of light cinnamon brown. ‘There are no spots on the thorax
but the dorsal surface of the oviducts beneath the muscles is dark cinnamon brown, and it shows through
very plainly; semen receptacles and testes dark orange yellow; eyes deep cinnamon brown.

(mississippiensis, of or belonging to the Mississippi River.)

Remarks.—With the exception of Argulus ingens, this is the largest species of the genus in eee,
and the measurements sometimes exceed those given above. For example, one female was found which
measured 20 mm. in length, while one of the males was 15 mm. long. In addition to its large size it
presents many peculiarities of structure, the most noticeable being the double lobes on the fourth legs,
the peculiar papillz on the sides of the anal sinus, and the complicated respiratory areas. One of these
parasites is as large as an ordinary copper penny and must drain the blood of its host quite severely.
Fortunately for the fish, it is rare to find more than one parasite on a single fish; otherwise they would
soon drain its blood. The present species completes the list and is the third found upon the gars, so
that each gar now has its peculiar parasite, Argulus lepidostei upon the long-nosed gar, A. mississippiensis
upon the short-nosed gar, and 4. ingens upon the alligator gar.

Argulus lepidostei Kellicott. (PI. Lxn, fig. 16-19; pl. Lxrv; pl. Lxv.)

Argulus, lepidostei, Kellicott, Bull. Buffalo Soc. Nat. Sci., vol. 3, p. 214, 1877; Wilson, Proc. U. S. Nat. Mus., vol. 2s,
p. 712, pl. 16.

Host and record of specimens.—Twenty males and twenty-one females were obtained from the short-
nosed gar, Lepisosteus platostomus, at Fairport, June 23, 1914, by Dr. A. D. Howard; they have been
given catalogue no. 43543, U.S. National Museum. One male and a female were taken from the long-
nosed gar, L. osseus, at Defiance, Ohio, by H. W. Clark; these have received catalogue no. 43522, U.S.
National Museum. Most of these were found near the pectoral fins of their host, as was recorded of the
original specimens by Prof. Kellicott.

Specific characters of female.—In addition to the descriptions given in the above references we may
note the following: The respiratory areas are situated close to the posterior end of the lateral lobes; the
outer and larger area is curved parallel with the margin of the carapace, its anterior end is narrowed,
while the posterior end is thickened; the smaller and inner area is elliptical in outline and is inserted
in the inner margin of the outer area near its anterior end (see fig. 29).

The ventral surface of the carapace is covered with orange-colored spines pointing backward. The
color of the living female is a pale lemon yellow in young specimens, with only a few spots of cinnamon
brown. These spots increase in size and number with advancing age and in full-grown adults become
continuous along the dorsal surface of the free thorax. The eyes are deep violet brown, the semen
receptacles a much paler yellowish brown.

Specific characters of male.—The accessory sexual apparatus of the male is complicated; the posterior
flap on the second legs is roughened and armed with short spines; the peg on the fourth legs has an
accessory peg distal to itself, which is solid and is not connected with the receptacle inside the first
peg; the boot-shaped flap on this leg has no heel.

On the third legs a long slender and flattened process extends outward from the anterior margin of
the ventral surface of the basal joint, parallel with the axis of the leg. Its tip is curved upward around
the end of the second basal joint and often extends back toward the body on the dorsal surface. Above
this process, on the anterior margin of the dorsal surface of the second joint, are two peculiar structures.

352 BULLETIN OF THE BUREAU OF FISHERIES.

The proximal one is a curved papilla, solid and thickly covered with short spines; the distal one is a
hollow conical papilla, split along its dorsal surface, its free edge and much of its dorsal surface covered
with short spines. In the posterior portion of this second basal joint is the usual semen receptacle
within easy reach of the peg on the fourth legs (see fig. 17).

The color of the male is similar to that of the female but paler; the brown on the dorsal surface of
the free thorax forms in adults a continuous line over the intestine; testes at first brownish yellow, then
light reddish brown, and finally cinnamon brown. The ventral surface of both sexes is pale yellowish
white without any pigment.

The newly hatched larva.—Two females of this species full of ripe eggs were captured July 3, 1914;
one of them laid a string of 30 eggs the following night and these all hatched on July 14, an interval of
ro days, the water being kept at the same temperature as that in the river (72° F.). This is the shortest
incubation period yet observed for any species of Argulus, and since the eggs were kept at the same
temperature as the river water it must be close to the normal period.

The eggs are similar to those of A. maculosus (Proceedings U. S. National Museum, vol. 32, pl. 31,
fig. 15), the chief differences being that they are not inclined to one another but are all in the same
straight line, and while there are two large jelly masses at the junction of every two eggs there is no
row of them standing out like the spokes of a wheel. The eggs were transparent and cream colored
when first laid but became opaque within 36 hours, and the eyes appeared on the fifth day.

The newly hatched larve are much more active than those of maculosus and swim about rapidly
with a steady gliding motion similar to that of the adult. At first they swim largely at the surface but
later sink to the bottom. They are much more heavily pigmented than any larve thus far observed,
especially through the center of the carapace and along the midline of the thorax, the pigment being
the same color as that of the adult.

Carapace broadly elliptical, the width to the length in the proportion of 13 to 14; anterior margin
evenly rounded and with a scattering fringe of very short hairs, amongst which are one or two longer
ones on either side; posterior sinus broad and very shallow; free thorax and abdomen forming a wide
triangle, whose base, the second thorax segment, is a little less than half the width and whose altitude
is a little more than half the length of the carapace. Abdomen half the width of the last thorax segment
and a Httle longer than wide; anal lamine small and rectangular, each armed with two short spines of
about the same length.

In the first antennz the hook of the basal joint is long and slender and reaches to the base of the
terminal joint; the latter is spherical and armed with seven large sete, whose tips reach beyond the
margin of the carapace, while all the rest of the appendage is covered.

In the second antenne the entire endopod projects beyond the carapace, the distal joint of the basipod
is twice the length of the proximal joint, the temporary exopod is curved backward, is distinctly three-
jointed, and is tipped with a single short spine.

The temporary mandibular palps are exactly like those of the maculosus larva, even to the spine
connected with their base. The second maxille (‘‘anterior maxillipeds’’) are also similar and termi-
nate in two sickle-shaped claws, of which the dorsal one is armed with three barbs.

The maxillipeds (“posterior maxillipeds’’) are five-jointed, the second and third joints armed on
their ventral surface with spines and bristles. The first swimming legs have a two-jointed basipod, the
distal joint armed along its anterior border with a row of short spines; the exopod is three-jointed and
ends in two short spines; the endopod is one-jointed and terminates in two long nonplumose sete. All
the other swimming legs are uniramose, immovable stumps, each ending in a short and blunt spine.
There are no traces of skin glands.

The eyes are large and close to the lateral margins; the ocelli are also exceptionally large and there
are only 1oor 12 ineacheye. The pattern of the median eye is also peculiar and very different from
that of any other species. The sting connected with the mouth is long and projects far in front of the
carapace.

Total length, 0.66 mm.; carapace, o.40 mm. long, 0.35 mm. wide.

Remarks.—This species is fairly common on the gars in the river, and as it was recorded by Kellicott
from the Niagara River at Buffalo it is probably as widely distributed as its host. Young specimens of
both sexes, fully developed but only 1.50 mm. in length, were obtained in the tow in considerable
numbers during the middle and latter part of August in several of the slews and in ‘‘Sunfish Lake,”
near Fairport.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 353

‘These tiny specimens were very active and moved about much more constantly and with more
speed than the free-swimming forms. They were so thin as to be almost perfectly transparent and made
excellent microscope mounts. Their abnormal abundance was doubtless due to the congested con-
ditions in the places where they were found, as already noted (p. 335).

Argulus stizostethii Kellicott. (Pl. Lx, fig. 20.)

Argulus stizostethii, Kellicott, Amer. Jour. Micros., vol. 5, p. 53; Wilson, Proc. U. S. Nat. Mus., vol. 25, p. 713, pl. 17.

Host and record of specimens.—This species was originally obtained by Kellicott from the wall-eye,
Stizostedion vitreum, in the Niagara River near Buffalo. Adult specimens have been obtained by the
author from wall-eyes and saugers, S. canadense, in the Mississippi River and from wall-eyes in Lake
Maxinkuckee. Young specimens of both sexes less than 1.50 mm. in length were taken in considerable
numbers in the tow at ‘Sunfish Lake,’’ near Fairport, August 2, 1914. These were associated with
A. lepidostei, the numbers of the two species being about even, but the males of both species much more
numerous than the females.

Specific characters of female.—These small Arguli being transparent, it was possible to make out the
nervous system with ease. Comparing it with that of other species, we may notice first the exception-
ally large size of the eyes, each of which is as large as the entire supraesophageal ganglion. The optic
nerves are also very large and swollen into a barrel shape.

The first of the ventral chain of ganglia is enlarged laterally to nearly twice the diameter of the
four following ones, which are all the same width, but the second and fifth ones are three times the
length of the third and fourth. The nerves are given off exactly like those in A. americanus (Proceedings
U.S. National Museum, vol. 25, p. 633).

The supporting rods in the membranous border of the sucking disks are made up of to or 12 parts;
the basal one is a narrow oblong with concave sides, the second, third, fourth, and fifth are much wider
but about the same length, convex posteriorly and concave anteriorly; the remaining parts are more or
less completely fused into a narrow threadlike rod.

The bordering fringe is narrow and made up of short and stiff hairs. The male was fully described
in the references above given, and there is nothing to add here.

Remarks.—This species is not as common as the preceding; it was originally obtained from the
wall-eye, but Kellicott records that specimens placed in an aquarium with the long-nosed gar and
some minnows fastened on them and eventually killed the minnows. This suggests that under natural
conditions they may often fasten on other fish than their usual host, especially under the conditions
prevailing in the slews and “‘lakes.”’

Its presence in such numbers in the tow is indicative that the species must be fairly common in the
vicinity.

Argulus appendiculosus Wilson.

Argulus appendiculosus Wilson, Proc. U.S. Nat. Mus., vol. 32, p. 419, pl. 32.

Host and record of specimens.—The types of this species were obtained from a sucker (species not
given) at Montpelier, Vt., and were sent to the United States Bureau of Fisheries at Woods Hole, Mass.,
in August, 1808.

Since the original description it has been found in several places in the Mississippi Valley, as follows:
A single female from the outside of the channel cat, Ictalurus punctatus, at Cumberland Falls, Ky.,
July 7, 1911, catalogue no. 39588, U. S. National Museum; a male and female from the outside of the
sheepshead, A. grunniens, at Lock 21 on the Cumberland River in Kentucky, catalogue no. 43523,
U. S. National Museum; several specimens of both sexes from the largemouth black bass, M. sal-
moides, at Fairport, Iowa, July 20, 1912, catalogue no. 43527, U. S. National Museum; two males and
two females from the outside of the redmouth buffalo, Ictiobus cyprinella, at Fairport, May 27, 1910,
catalogue no. 43542, U. S. National Museum; a male and female from the smallmouth buffalo, J. bubalus,
at Fairport, June 28, 1914, catalogue no. 47761, U. S. National Museum. Isolated specimens were also
obtained from the gizzard shad, Dorosoma cepedianum, the crappie, Pomoxis annularis, and the white
bass, Roccus chrysops, which goes to prove that these fish at least serve as occasional hosts.

Remarks.—This species was established in 1907 upon 20 specimens taken from a sucker at Mont-
pelier, Vt., and both sexes were fully described and figured in the reference above given. All that can
be added here is a few data with reference to the color. Both sexes when alive are a transparent creamy
white, covered on the dorsal surface of the carapace and abdomen with opaque white dots, circular in

354 BULLETIN OF THE BUREAU OF FISHERIES.

outline, very minute and thickly scattered, especially near the margin of the carapace. On the carapace
there are also blotches of pale reddish brown, much larger than the white spots and more widely scattered.
Each blotch has a small spot near the center where there is no pigment; immediately around this spot
the pigment is deeper in color and pales gradually toward the edges. The dorsal surface of the thorax
over the eggs is a rich golden yellow, thickly streaked with longitudinal rows of purplish brown blotches,
smaller than those on the carapace, deeper in color, more uniform in size, and more regular in shape.
Most of these blotches also have small circular spots free from pigment, sometimes two to four in the
same blotch and of different sizes. The eyes are deep golden yellow, each separate facet with a dark
purple center. The sperm receptacles are golden yellow.

Although the species was originally found outside of the Mississippi Valley, there seems to be no
doubt that it belongshere. Its wide distribution and the variety of hosts show that its range is universal
throughout the eastern and central United States.

Argulus ingens Wilson.

Argulus ingens Wilson, Proc. U. S. Nat. Mus., vol. 42, p. 233, pl. 30.

Host and record of specimens.—Both sexes of this species were obtained from the alligator gar, Lepiso-
steus tristoechus, at Moon Lake, Miss.

No alligator gars were captured during the present summer, but they are fairly common in the
Mississippi River, and when carefully examined will probably yield specimens of this parasite.

Argulus nobilis Thiele.

Argulus nobilis Thiele, 1904, Mitteil. aus dem Zool. Mus. Berlin, II Band, 4 heft, p. 28, pl. 7, 8, fig. 64-76.

Host and record of specimens.—Thiele found six females and one male of this species among the
specimens of the Berlin Zoological Museum; the name of the host upon the museum label was given as
““Lepidosteus aculeatus.’’ No such association of names is known in ichthyological literature, noris
there any hint as to whether the mistake was made in the generic or the specific name, so that we are left
in a quandary as to its identification. Thiele suggested that it may have been “ L. viridis,’’ which is the
name given by Giinther to the alligator gar, but this was only a guess and was unaccompanied by any
proof.

Remarks.—The present species differs from ingens in the relative size of the abdomen and carapace,
in most of the details of the first and second antenne, in the general structure and armature of the
maxillipeds, and especially in the accessory sexual apparatus of the second and third swimming legs
of the male. The two species resemble each other in their exceptionally large size, in the general form
of the abdomen, and in the approximation of the two outer spines on the basal plate of the maxillipeds.
Nothing is stated with reference to the respiratory areas of nobilis, but those of ingens are very peculiar,

If Thiele’s conjecture that the alligator gar is the host of this species should prove true, it would
greatly increase the probability that ingens and nobilis are synonymous, and Thiele’s name would take
precedence.

At present, however, there are so many specific differences, and the identity of the host is so uncer-
tain, that we can only leave the species as described and await future developments.

Argulus maculosus Wilson.

Argulus maculosus, Wilson, Proc. U.S. Nat. Mus., vol. 25, p. 715, pl. 19.

Host and record of specimens.—The original types of this species were 11 females and 3 males, found
unlabeled in the National Museum collection, and a single female from the muscalonge, Esox nobilor,
at Clayton, N. Y. Since then two females were obtained from the red-eye, Ambloplites rupestris, at
Lake Maxinkuckee, Ind., August 8, 1906, and a single female from the yellow catfish, Amezurus natalis,
August 22, from the same locality. Numerous specimens were subsequently obtained from the two
catfish, Ameiurus nebulosus and A. natalis, at Lake Maxinkuckee, and these are evidently their true
hosts. (Proceedings U. S. National Museum, vol. 32, p. 416).

Some egg strings were obtained from these last ripe females and have received catalogue no. 32826,
U. S. National Museum; the newly hatched larve (catalogue no. 32822, U. S. National Museum) were
fully described in the last reference above given.

Remarks.—There is nothing to add to the full descriptions already given. Only one mutilated
specimen has yet been found from the Mississippi River, but as the two catfish are plentifully distributed
throughout the valley no doubt more will be discovered in the future.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 355

Argulus versicolor Wilson.

Argulus versicolor Wilson, Proc. U. S. Nat. Mus., vol. 25, p. 716, pl. 20; vol. 27, p. 643, fig. 22-33, text.

Host and record of specimens.—This species was originally obtained from the common pickerel,
Esox lucius, at Warren, Mass. It was also found at other localities in the same State. A male and
female were taken from the same host at Lake Maxinkuckee, Ind., August 15, 1906.

Remarks.—The single pair above mentioned are the only specimens of this species thus far found
in the Mississippi Valley, but the host is one of the most widely distributed fish in America and other
specimens should be discovered in the future. They are usually found inside the mouth or in the gill
cavity and not on the outside surface.

Argulus catostomi Dana and Herrick.

Argulus catostomi Dana and Herrick, Amer. Jour. Sci., vol. 31, p. 297, unnumbered plate; Wilson, Proc. U. S. Nat. Mus.,

vol. 25, p. 709, pl. 13; vol. 32, p. grr, pl. 209. P

Host and record of specimens.—This species was originally found upon a sucker near New Haven,
Conn. It was taken by the present author from Catostomus bostonensis in Massachusetts, and from
C. catostomus at Lake Maxinkuckee, Ind., and from C. nigricans and C. catostomus in the Missequoi
River at Swanton, Vt. The Maxinkuckee specimens have been given catalogue no. 32820, U.S. National
Musevm.

Remarks.—Only one or two suckers were taken during the summer of 1914 and no specimens were
found upon them, but the species is in the valley and is probably as widely distributed as its host.

Argulus americanus Wilson.

Argulus americanus Wilson, Proc. U.S. Nat. Mus., vol. 25, p. 718, pl. 21; vol. 27, p. 627, fig. 1-21, text.

Host and record of specimens.—Originally obtained by Prof. Reighard from Amia calva in the labo-
ratory aquaria at Ann Arbor, Mich., this species was afterward found on the same host at Lake Maxin-
kuckee, Ind. (catalogue no. 32825, U. S. National Museum), and at Fairport, Iowa, August 26, 1912
(catalogue no. 43601, U. S. National Museum), and on Umbra limi in one of the AGRnE at Fairport,
Iowa, February 7, 1911 (catalogue no. 43529, U. S. National Museum).

Remarks.—This species is a great aquarium pest and thus is more likely to attract notice than some
of the others. It is widely distributed throughout the valley but fortunately sticks closely to the dogfish
forahost. Its presence on the mud minnow as above recorded was probably only temporary, and appar-
ently it does not infest other fish.

Both sexes of the adults and the larve are fully described and figured in the references given above.

Argulus trilineatus Wilson.

Argulus trilineata Wilson, Proc. U.S. Nat. Mus., vol. 27, p. 651, fig. 34-38, text.

Host and record of specimens.—The type was a female taken from goldfish in an aquarium at Macon,
Ga. Another female was obtained by L. V. Lewis in a bowl of goldfish at Henderson, Ky., October
30, 1914, and sent to the National Museum for identification. It was afterward returned to Mr. Lewis.

Remarks.—In the reference given above the specific name ended in the letter “a’’ through an
oversight of the author; it should end in “‘us’’ so as to agree with the genus name, and that change is
here made.

It was gratifying to obtain a second specimen from Kentucky and thus to know that the species
was a valid one and quite widely distributed. This latter location comes within the range of the present
paper and so the species is here included.

Argulus funduli Krgyer.

Argulus funduli Kréyer, Naturhistorisk Tidsskrift, 3 Raekke, 2 bd., p. 92.

Host and record of specimens.—Kréyer found this species on the gills of a species of Fundulus near
New Orleans. While this brings it into the Mississippi River, its host is a marine or brackish-water
fish, and hence the parasite does not rightly belong among the fresh-water forms. The present author
has found it repeatedly at Beaufort, N. C., and at Woods Hole, Mass., but always in salt water.

356 BULLETIN OF THE BUREAU OF FISHERIES.

ERGASILIDA.

Ergasilus lanceolatus, new species. (Pl. LXvi, fig. 40-46.)

Host and record of specimens.—Twenty females with egg strings were obtained from the gills of the
gizzard or hickory shad, Dorosoma cepedianum, at Lock 21 on the Cumberland River in Kentucky, July
16, 1911. This lot has been given catalogue no. 43555, U. S. National Museum, and from it has been
selected a single female (catalogue no. 43556, U. S. National Museum) to serve as the type of the new
species.

Specific characters of female.—General body form long and narrow, lanceolate; cephalothorax ellip-
tical, one-half longer than wide, almost squarely truncated posteriorly, projecting a little anteriorly,
with a small knob at the center of the anterior margin. First three free segments narrowed regularly
backwards, the first of them (second segment) a little more than half the width of the carapace and
about twice the width of the fourth segment; fifth segment very short and narrow; genital segment one-
half wider than the fifth segment, with strongly convex sides. Abdomen the same width as the fifth
segment, three-jointed, the basal joint longer than the others; anal laminz small, rectangular in out-
line, each armed with two sete, the inner of which is 7 or 8 times the length of the outer one.

First antenne six-jointed, the basal joint much longer than any of the others and armed with a
very long, jointed seta, the other joints carrying shorter and simple sete. Second antennae not very
large but powerful, basal joint short but much swollen and projecting strongly on the outer margin;
second joint with a small stout spine near the center of the inner margin; terminal claw long, stout, and
strongly curved.

The mouth parts project much more strongly than in any species thus far examined, both the
upper and the under lips standing out prominently to form a long and sharp cone, from whose summit
project on either side the long first maxilla. Mandibles exceptionally large and thickset, the terminal
portion turned forward at right angles to the basal. The latter carries on its anterior margin, just out-
side the narrow neck, a bluntly rounded process projecting forward; the cutting blade is triangular in
outline and armed with sete along its inner margin only.

The palp is exceptionally long; starting from the posterior corner of the basal joint and reaching
nearly to the center of the cutting blade with a row of corrugations along its outer margin.

First maxille small but projecting strongly, each armed with two plumose setz; second maxilleze
much smaller than the mandibles, but otherwise of the usual size and pattern. Endopods of the first,
third, and fourth legs longer than the exopods; exopods of second legs longer than the endopods; all
three joints of the endopods of the first legs and the two basal joints of the endopods of the second legs
armed with minute teeth along their outer margins; exopod of fourth legs two-jointed, the basal joint
twice the length of the terminal one. The arrangement of spines and sete is as follows: First exopod,
I-0, 0-0, 1-5; endopod, o-1, o-1, 1-4; second exopod, mI-o, 1-1, 1-6; endopod, o-1, 0-2, 1-4; third
exopod, I-o, o-1, o-6; endopod, o-1, o-2, 1-4; fourth exopod, o-o, 1-4; endopod, o-1, o-1, I-2.

The egg strings when first extruded are conical, largest at the base and tapering to a single egg at
the tip; when fully developed they are cylindrical and considerably shorter than the body; eggs in
5 or 6 rows, about Io eggs in a row.

Color (preserved material), a uniform light brown without pigment markings.

Total length, 1 mm.; cephalothorax, o.60 mm. long, o.40 mm. wide. Length of egg strings, 0.60
to o.80 mm.

(lanceolatus, lanceolate, alluding to the general body shape.)

Remarks.—This species is not associated as yet with any glochidium, but may well take the place of
ceruleus or centrarchidarum or versicolor.

Its presence on the shad indicates that this fish would make a good host for some of the gill glochidia
as well as for those already found upon its fins. Like other parasites found upon the herrings and their
close relatives, this species does not infest any fish except its immediate host, and hence it is not likely
to be found except on the gizzard shad.

Ergasilus nigritus, new species. (Pl. Lxvm.)

Host and record of specimens.—Ten females, most of them with egg strings, were obtained from the
gills of the largemouth bass Micropterus salmoides, in the Mississippi River at Fairport, Iowa, July 20,
1914. They have received catalogue no. 43562, U. S. National Museum, and become cotypes of the

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 357

new species, while a single female (catalogue no. 43561, U. S. National Museum) has been selected to
serve as the type.

Specific characters of female.—General body form short and squat; cephalothorax three-quarters of
the entire length, one-fifth longer than wide, and strongly flattened dorsoventrally; dorsal surface mod-
erately convex, ventral surface flat, with the mouth projecting but little, if any.

Antennal area rectangular in outline with rounded corners and projecting strongly anteriorly, so
that the bases of both pairs of antenne are carried in front of the body of the carapace. This latter is
about as long as wide, is slightly narrowed posteriorly, and shows a distinct dorsal groove and marginal
sinus separating the head from the first thorax segment, which is only one-fifth the length of the head.
Second (first free) segment abruptly narrowed to half the width of the first and very short; remaining
thorax segments also short and narrowed regularly backward; fifth segment concealed dorsally between
the fourth and genital segments; the latter considerably wider and three times the length of the fourth
segment, with strongly convex sides. Abdomen three-jointed, joints about the same length but nar-
rowing posteriorly and indistinctly differentiated; anal lamine small and rectangular, each bearing two
sete, of which the inner one is twice the length of the outer, and about the same length as the free thorax
and abdomen.

Egg strings ovate and strongly divergent, only one-fourth longer than wide, and so much inflated
that they meet dorsally at the midline; eggs large, arranged in eight or nine longitudinal rows, about
seven eggs in the longest rows. First antenne six-jointed, the penultimate and basal joints longer
than the others and all the joints heavily armed with sete; second antenne long and stout, the basal
joint much inflated and quite convex externally, the terminal claw stout and strongly curved.

Mouth parts rather small and effectively concealed beneath the upper lip, not projecting as in other
species but flattened with the rest of the ventral surface. Mandibles with a narrow cutting blade,
armed with sete along the inner margin only; palp about as long as the cutting blade, armed with setz
or toothed along the posterior margin.

First maxille with a large base and two stout sete; second maxille with a straight cutting blade,
fringed with sete along both margins, basal joint large and rectangular. Endopods of first and
fourth legs much longer than exopods, the two rami of the second and third legs equal; exopod of fourth
legs two-jointed. The arrangement of the spines and sete is as follows: First exopod, I-o, o-1, 1-5;
endopod, o-1, o-2, I-4; second exopod, I-o, o-1, 0-6; endopod, o-1, I-2, o-5; third exopod, o-o, o-1, 0-5;
endopod, o-1, o-2, o-5; fourth exopod, o-o0, o-4; endopod, o-1, o-2, o-5.

Color (preserved material), young females a uniform creamy white without pigment; in later
development black pigment appears in scattered spots on the dorsal surface of the carapace and gradu-
ally covers the entire copepod, including even the swimming legs and anal lamine and sete but not
the second antennez.

Total length, 0.70 mm.; carapace, 0.50 mm. long, 0.40 mm. wide. Egg strings, 0.35 mm. long, 0.23
mm. wide.

(nigritus, blackened.)

Remarks.—This tiny species may be recognized at once by the jet-black color of the mature adults
and by the very short and thickset egg strings.

It can not be very common, since only the single lot has been obtained from many hundreds of
largemouth black bass which have been examined for copepod parasites. It seems to take the place
on this bass of ceruleus upon the other Centrarchide, being associated with Lampsilis glochidia.

Ergasilus megaceros, new species. (Pl. xvi, fig. 49; pl. Lxvm, fig. 57-61.)

Host and record of specimens.—Four females, two of which had egg strings, were taken from the
lamellar plates in the nasal fosse of a Fulton cat, Ictalurus anguilla, captured at Fairport, Iowa, May
16, 1914. Three of these specimens have been given catalogue no. 43548, U. S. National Museum, and
become cotypes of the new species, the fourth and best one (catalogue no. 43544, U. S. National Museum)
becoming the type.

Specific characters of female.—General body form long and slender; cephalothorax ovate, one-half
longer than wide, narrowed and pointed anteriorly, squarely rounded posteriorly; first thorax segment
as wide and half as long as the head and separated from the latter by marginal sinuses and a distinct
dorsal groove; eye far forward just behind the bases of the first antenne; thorax segments diminishing
regularly in size backward, the fifth one very short; genital segment the same width as the fourth seg-

358 BULLETIN OF THE BUREAU OF FISHERIES.

ment, with strongly convex sides. Abdomen three-jointed, the joints all about the same width and
length; anal lamine nearly as long as the entire abdomen, narrow and enlarged at the tip into a rounded
knob on the outer margin, each tipped with two long plumose sete, the inner of which is one-half
longer than the outer. Egg strings elongate ellipsoids, a little shorter than the cephalothorax; eggs
large, arranged in 6 or 7 longitudinal rows, about 8 eggs in the longest rows.

First antenne exceptionally large, six-jointed, the jointing indistinct, the fourth segment carrying
on the inner distal corner a huge jointed seta, which reaches back to the center of the second thorax
segment; the terminal joint is tipped with another huge seta, unjointed but nearly as long as the jointed
one. Second antenne also long but slender, the terminal claw bluntly rounded. Mouth tube pro-
truding strongly; mandibles with a short neck and cutting blade, turned forward diagonally; palp long
and narrow and armed along its inner margin with short bristles.

First maxilla of the usual pattern; second maxille meeting on the midline, the cutting blade short
and small and armed with a few sharp spines. Endopods of the first and fourth legs longer than the
exopods; rami of the other legs equal; arrangement of the spines and setz as follows: First exopod,
I-o, I-1, I-6; endopod, o-1, o-1, 0-6; second exopod, I-o, I-1, I-5; endopod, o-1, o-2, 1-4; third exopod,
I-o, I-1, I-5; endopod, o-1, o-2, 1-4; fourth exopod, I-o, 1-4; endopod, o-1, 0-2, I-3.

Color, a transparent yellowish white, oviducts white, egg tubes yellow, the ventral surface of the
carapace and thorax covered with irregular patches of a light sky-blue pigment.

Total length, 1 mm.; carapace, o.50 mm. long, 0.40 mm. wide; first antenne, including setz, 0.60
mm. long. Egg strings, 0.40 mm. long.

(megaceros, uéyas, large, and xépas, horn, alluding to the large first and second antennz.)

Remarks.—So far as known, this is the first parasitic copepod to be found in the nasal fosse of any
fresh-water fish. They are common in both the nasal fosse and spiracles of salt-water fish, sharks, and
rays, and probably the reason why they have never been found in fresh-water fish is simply because
they have never been looked for. The nostrils of this catfish were only quarter of an inch in diameter,
and hence the ergasilid larva must do some strenuous hunting to find its chosen place on the host. It
is more than likely that the examination of similar fossee on other large fresh-water fish will yield speci-
mens of this or similar species. Being found thus in the nose, the species can not be associated in any
way with mussel glochidia, but its presence emphasizes the testimony of those species found on the
gills, that the Fulton cat would make a good host for glochidia. If the ergasilid larva can find its way
into the nose of these fish, it is possible that the mussel glochidium can perform the same feat. At all
events it will be worth while to examine the nose of large fishes for both copepods and ylochidia.

Ergasilus elongatus, new species. (Pl. uxvI, fig. 47, 48; pl. uxvit, fig. 62-66.)

Host and record of specimens.—Twenty-five females with egg strings were obtained from the gill
rakers of the spoonbill cat, Polyodon spathula, from the Mississippi River at New Boston, Ml., July,
1914, catalogue no. 47764, U. S. National Museum. Thirty females from the same host at Keokuk, Iowa,
August 28, 1914, catalogue no. 47763, U. S. National Museum. A single female (catalogue no. 4776s,
U. S. National Museum) has been selected from this last lot to serve as the type of the new species.
Sections of two gills of the same fish, with specimens of the species in situ, have received catalogue no.
47762, U. S. National Museum.

Specific characters of female.—General body form an elongate ovoid, the larger end anterior; cephalo-
thorax one-half longer than the rest of the body, widest at its center, strongly tapered anteriorly, almost
squarely truncated posteriorly. Antennal area reaching the entire width of the anterior end and dis-
tinctly separated from the rest of the head.

Free thorax segments diminishing regularly in width and length from in front backwards; fifth
segment plainly visible and half the width of the fourth; genital segment barrel shaped, its sides mod-
erately projecting. Abdomen segments the same length but diminishing regularly in width; anal
laminz half as long again as the last abdomen segment, narrow with square corners, each tipped with
two short setz, the inner of which is one-half longer than the outer. Egg strings to the entire length of
the body as 8 to 11, rather narrow; eggs arranged in 6 or 7 longitudinal rows, about 25 in the longest rows.

First antenne rather slender and short, six-jointed, and sparsely armed with sete; second antennze
also short but stout, not long enough to reach more than halfway around the gill raker, but clasping it
so tightly as to make a groove init. Mouth tube exceptionally far forward and not projecting as strongly
as in most species; upper lip rather square, and entirely covering the mouth parts. Mandibles as large

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 359

as the second maxillez, cutting blade turned forward at right angles to the base, very wide and armed
with setz along both margins; palp short and narrow, with a row of comblike teeth along its inner margin.
First maxille small and inconspicuous, not visible in side view owing to the fact that they are covered
by the upper lip; second maxillz small, the cutting blade narrow and armed with sete along both
margins. This species resembles elegans in having the endopod of the first legs as well as the exopods
of the fourth pair two-jointed.

The arrangement of the spines and setz is as follows: First exopod, I-o, 1-2, 1-5; endopod, o-1,
m-6; second exopod, I-o, I-1, I-7; endopod, o-1, o-2, 1-5; third exopod, I-o, 11-0, I-5; endopod, o-1,
0-2, II-5; fourth exopod, o-o, 1-5; endopod, o-1, o-2, 1-4. The oviducts are so arranged that when
filled with ripening eggs they do not distort the shape of the cephalothorax as in other species.

Color, a transparent grayish white, oviducts and egg strings dark yellow, ventral surface covered
with an interlaced network of lines and patches of indigo blue.

Total length, 1.40 mm.; cephalothorax, 0.85 mm. long, 0.30 mm. wide. Egg strings, 1 mm. long.

(elongatus, elongate, alluding to the general body form.)

Remarks.—This species is unique in its general body form as well as in its habitat and may be
recognized by either peculiarity. It will be remembered that in the paddle fishes, to which the spoon-
bill cat belongs, the gill rakers are very long and slender and in a double series on each gill arch, the
series separated by a broad membrane. These copépods were fastened to the rakers, sometimes on the
outside, sometimes on the inside between the raker and the membrane, with their head indifferently
in either direction, toward the arch or away from it, and the short but stout second antennze grasped the
raker firmly enough to make around it a groove from which the copepod could not be separated except
by cutting the raker close to the antenne.

So far as known this is the only instance of any of the Ergasilide fastening itself to the bony gill
rakers instead of the soft filaments, and this makes the strength of the attachment the more worthy of
notice.

Apparently this species is not connected with any glochidium, but this may be changed later when
the spoonbill cat has been further and more extensively examined. The body is fully as thick as it
is wide and the carapace fits snugly on the general contour, giving the copepod a peculiarly clean and
graceful appearance.

Ergasilus elegans, new species. (PI. Lxrx, fig. 67-73.)

Host and record of specimens.—This species was captured several times in the tow at Patterson
Lake and ‘‘Sunfish Lake’’ before it was found on any fish host; these free-swimming specimens have been
given catalogue no. 47767, U.S. National Museum, and are all without egg strings. A second lot with egg
strings was obtained from the gills of the bullhead, Amezurus melas, caught in ‘‘Sunfish Lake,’’ August
24, 1914; they have been numbered catalogue no. 47768, U. S. National Museum. A single female
has been selected from this lot to serve as the type of the new species, with catalogue no. 47769, U. S.
National Museum. A few were also obtained from the gills of the long-nosed gar, Lepisosteus osseus, in
the Mississippi near Fairport, Iowa, catalogue no. 47766, U. S. National Museum. Others were found
on the gills of the short-nosed gar, L. platostomus, from Patterson Lake, August 6, 1914.

Specific characters of female.—General body form elongate; cephalothorax one-half longer than wide,
the first thorax segment distinctly separated from the head and somewhat narrower; carapace well
rounded and scarcely projecting anteriorly; antennal area poorly differentiated.

Second, third, and fourth thorax segments about the same length and diminishing regularly in width,
fifth segment scarcely visible; genital segment barrel-shaped, with moderately projecting sides. Abdo-
men three-jointed, joints about the same length but diminishing slightly in width; anal sete as long as
the last two segments, twice as long as wide, with square corners, each tipped with two sete, a longer,
jointed one at the inner corner, and a shorter oblique one at the outer corner.

Egg strings less than half the length of the body and rather wide; eggs exceptionally large and
arranged in two rows, 15 or 18 eggs in each string. First antenne six-jointed and heavily armed with
sete; second antenne very long and slender, basal joint short and not swollen; second joint and terminal
claw the same length, the former with a small spine on its ventral surface, the latter bent into a half circle.
Mandibles with a rectangular base abruptly narrowed into the neck, which is half as long as the base
and is tipped with a triangular cutting blade, heavily fringed with sete around its entire margin; palp
as long as the cutting blade, narrow and armed along the inner margin with a row of heavy, comblike

16825°—16——3

360 BULLETIN OF THE BUREAU OF FISHERIES.

teeth. First maxilla small but protruding well and armed with long sete; second maxille with a
broadly triangular blade, fringed only along its posterior margin; muscles and rudiments of the maxilli-
peds present behind the second maxilla; lower lip a small narrow, semicircular piate behind the tips of
the second maxilla. Endopod of the first swimming legs and exopod of the fourth legs two-jointed; all
the other rami three-jointed; arrangement of the spines and sete as follows: First exopod, I-o, o-1, 1-5;
endopod, o-1, 11-5; second exopod, I-o, o-1, I-6; endopod, o-1, o-2, 1-4; third exopod, I-o, o-1, I-5;
endopod, o-1, o-2, I-4; fourth exopod, I-o, I-5; endopod, o-1, 0-2, I-3.

Ground color that of transparent cartilage, covered over the entire ventral surface with large irregular
patches of deep purplish blue; these coalesce into a line along either side of the digestive tract, which
latter is a rich golden yellow; on the bases of the antennz and mouth parts, around the eyes, and out-
side the blue line in the genital segment are patches of pale brick red; the compound eye is dark purple.

Total length, 1.25 mm.; cephalothorax, 0.60 mm. long, o.40mm. wide. Egg strings, 0.50 mm. long.

(elegans, elegant, neat in appearance.)

Remarks.—This species closely resembles versicolor, but can be readily distinguished by the two-
jointed endopod of the first legs. From all the other species it is at once distinguished by its varied
coloration, as well as by its free-swimming habits. It is associated with Lampsilis anodontoides, the
yellow sand-shell, and apparently with no other glochidia. Accordingly it is likely to be found upon
the alligator gar at the right season.

In swimming the large second antennz are folded like arms across the thorax, and neither they nor
the first antenne are used for locomotion.

Movement is accomplished entirely by means of the swimming legs and consists of a series of rapid
dashes, without any particular direction.

These movements are swifter and they carry the copepod many times farther than those of the
regular free-swimmers, so that if the tow be placed in a large shallow glass these free-swimming parasites
can be at once detected by their movements. Apparently this species swims about freely in the slews
until its eggs are ripe, since the females obtained from the tow are fully as large as those from the fish.

Like the young Arguli they frequent the surface in the daytime and sink to lower depths at night,
and they must fasten upon the fish when fully matured rather than in a larval stage.

Ergasilus ceruleus Wilson. (Pl. Lx1x, fig. 74.)

Ergasilus ceruleus Wilson, Proc. U. S. Nat. Mus., vol. 39, p. 334, pl. 43.

Host and record of specimens.—When this species was established it was found only upon bluegills
in Tippecanoe Lake and Twin Lakes, Ind. Here in the Mississippi River, however, it is extremely
abundant; its chief hosts are the two crappies, Pomoxis annularis and P. sparoides.

From the former lots have been obtained which have received catalogue no. 43531, 43535, 43539,
43532, U. S. National Museum; from the latter the lots are catalogue no. 43545, 43514, U. S. National
Museum. Catalogue no. 43541, U. S. National Museum, contains a set of gills just as they were taken
from P. annularis, with the parasites preserved in situ, and nearly 500 of them upon the single fish.

A single female (catalogue no. 43538, U. S. National Museum) was obtained from the blue-spotted
sunfish, A pomotis cyanellus; several (catalogue no. 47774, U. S. National Museum) were taken from the
bluegill, Eupomotis gibbosus, captured near Fairport, Iowa; two were found on the sauger, Stizostedion
canadense (catalogue no. 47776, U. S. National Museum); three on the gills of the white bass, Roccus chry-
sops (catalogue no. 47777, U. S. National Museum); and one on the gills of the long-nosed gar, L. osseus.
These fish were all captured in the Mississippi River at or near Fairport during the present season.

Newly hatched nauplius larva.—Some of the females obtained on August 14 were carrying eggs whose
blue color showed that they were ready tohatch. These were accordingly placed in a suitable aquarium
and all hatched out on the following day. The issuing nauplius proved to be quite similar to that of
Ergasilus centrarchidarum, but with these differences:

General body form ovate, considerably narrowed and pointed posteriorly, and nearly twice as long
as wide; the knob at the posterior end, the future abdomen, is much larger than in centrarchidarum and
projects farther. The three pairs of appendages are similar in all their general features to those of the
other Ergasilide and differ only in little details. The basal joint of the first pair is somewhat swollen;
the masticatory process on the second pair is proportionally large and carries a very long spine which
is not much curved; the lamina shaped like the blade of a case knife, found upon the endopod of the
third appendages, is sometimes jointed and is relatively large.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 361

The upper lip is diamond shaped, considerably longer than wide, the anterior end well rounded,
the posterior end pointed, and reaching some distance behind the masticatory processes of the second
antenne.

The balancers at the posterior end of the body are straight instead of curved and stand at an angle
of about 45 degrees with the body axis.

Remarks.—The large numbers (500 or more) of specimens found upon a single fish are worthy of
notice; in some instances it does not seem as if any more could be crowded upon the gills, three or four
copepods being found, one above another, upon the same filament. Like the original specimens from
the bluegills, they are always found on the inner side of the gill filament, between the rows of filaments
on the same arch.

Here in the Mississippi Valley the two crappies are evidently the chief hosts of the species and it
is worthy of note that they are vegetable feeders like the bluegill. This species of Ergasilus therefore
may be fairly regarded as a parasite of the vegetarian Centrarchide.

It is also worth recording that of the many hundreds of ceruleus examined every one was scrupu-
lously clean; there were no protozoa or alge upon any of the specimens. ‘This is in marked contrast to
the following species from the catfishes, nearly every specimen of which is covered with these para-
sites. The present species is associated with the Lampsilis group of glochidia and has been found upon
every species of fish that serve as hosts for these glochidia except the sheepshead and the largemouth
black bass, on which latter fish it is replaced by E. nigritus, a new species.

Ergasilus versicolor Wilson.

Ergasilus versicolor Wilson, Proc. U. S. Nat. Mus., vol. 39, p. 341, pl. 4s.

Host and record of specimens.—Originally found upon two species of catfish at Lake Maxinkuckee,
Ind., this ergasilid proves to be even more abundant upon the catfishes of the Mississippi, and the fol-
lowing lots were obtained during the summer: Catalogue no. 43558, U. S. National Museum, from the
gills of the skipjack, Pomolobus chrysochlorus, taken in Lake Pepin and seat to Fairport July 23; cata-
logue no. 47770, U. S. National Museum, from the gills of the channel cat, Ictalurus punctatus, taken at
Fairport July 25; catalogue no. 43533, U. S. National Museum, from gills of channel cat taken at Fair-
port September 2, 1910; catalogue no. 43560, U. S. National Museum, from gills of the bullhead, A mei-
urus nebulosus, taken in Patterson Lake July 3; catalogue no. 43509, U. S. National Museum, from
gills of the Fulton cat, Ictalurus anguilla, taken at Fairport May 14, 1914.

Remarks.—All these specimens except those included in no. 47770 were heavily infested with
parasitic protozoa and fresh-water alge, and some were so thoroughly covered as to be effectively con-
cealed. This is probably due in part to the feeding habits of their hosts, all of whom stick close to the
mud at the bottom of the river.

The species is associated with the Quadrula group of glochidia and in all probability will be found
upon Leptops olivaris, the mud cat.

Ergasilus centrarchidarum Wright.
Ergasilus centrarchidarum Wright, Proc. Canadian Institute, n. s., vol. 1, p: 243, pl. 1; Wilson, Proc. U. S. Nat. Mus., vol.
39, D- 331, pl. 42.

Host and record of spectmens.—In addition to those found upon various hosts at Lake Maxinkuckee,
Ind., and recorded in the last reference given above, the following lots were obtained during the past
summer: Catalogue no. 43507, U. S. National Museum, from the gills of Pomoxis annularis, taken in the
Mississippi at Fairport, May 25, 1910; catalogue no. 43537, U. S. National Museum, from the gills of the
largemouth black bass, M. salmoides, taken in Crooked S Slew, Fairport, May 26, 1910; catalogue no.
47778, U.S. National Museum, from the gillsof the white bass, Roccus chrysops, taken at Fairport, August
6; catalogue no. 47775, U. S. National Museum, from the gills of the sauger, S. canadense, taken at Fair-
port, August 14; catalogue no. 47779, U. S. National Museum, from the gills of the largemouth black
bass, taken in Patterson Lake, August 6; catalogue no. 47780, U. 5. National Museum, from the gills
of the warmouth, Chenobryttus gulosus, taken in Patterson Lake, August 6. A single female was also
obtained from the gills of the green sunfish, A pomotis cyanellus, taken at Fairport, August ro.

Remarks.—This species is frequently associated with ce@ruleus upon the same host, but the two can
always be separated by their position on the gill filaments; centrarchidarum is always on the outside,
while ceruleus is as constantly on the inside between the two rows of filaments, and no exception has
yet been found to this rule.

362 BULLETIN OF THE BUREAU OF FISHERIES.

This species is associated with glochidia of the Quadrula group, and its presence in considerable
numbers upon any fish indicates that its host would make a good carrier of Quadrula glochidia. It is
worthy of note that these two species, centrarchidarum and ceruleus, which accompany the two groups
of glochidia, are associated upon those fish which serve as hosts for the glochidia and are often found
together, while centrarchidarum and versicolor are never found upon the same fish although they accom-
pany the same group of glochidia.

Ergasilus chautauquaensis Fellows. ,

Ergasilus chautauquaensis Fellows, Proc. Amer. Soc. Microscopists, vol. 9, p. 246, 1 plate, unnumbered; Wilson, Proc.

U.S. Nat. Mus., vol. 39, p. 343, pl. 46.

Host and record of specimens.—This species was originally discovered in the tow of Lake Champlain
and both sexes were afterwards found by the present author in some samples of tow from Lake Mendota
at Madison, Wis.; these specimens received catalogue no. 38617, U. S. National Museum. It has not
thus far been found upon any fish, but in all probability its habits are like those of the new species elegans.
The males are free-swimmers throughout life and the females swim freely until their eggs are ready to
pass out into the external sacks. The present species will probably be found at another time of year
upon the gills of some fish in Lake Champlain or Lake Mendota.

Ergasilus funduli Krdyer.

Ergasilus funduli Kréyer, Naturhistorisk Tidsskrift, (3), vol. 2, p. 228, pl. x1, fig. x, a-f; Wilson, Proc. U. S. Nat. Mus.,

vol. 39, p. 328. ;

Host and record of specimens.—Kr¢yer found a few specimens of this species on the gills of Fundulus
ocellaris (F. limbatus Krdyer) taken near New Orleans in the Mississippi River. This is another of the
marine or brackish water fish that comes up the river a little ways, but its parasites can not be regarded
as true fresh-water species.

Ergasilus lize Krgyer.

Ergasilus lize Kréyer, Naturhistorisk Tidsskrift, (3), vol. 2, p. 232; Wilson, Proc. U. S. Nat. Mus., vol. 39, p. 340.

Host and record of specimens.—This is another species captured by Krgyer near New Orleans on the
gills of Mugil curema (M. liza Krgyer). Like the preceding, it can not be regarded as a true fresh-water
species, neither have any further specimens ever been found.

LERNAOPODID.

Salmincola californiensis (Dana). (PI. Lxx.)

Lerneopoda californiensis Dana, U.S. Exploring Expedition during the years 1838 to 1842, vol. 12, p. 1379, pl. 96, fig. 1a, rb.

Salmincola californiensis Wilson, Proc. U. S. Nat. Mus., vol. 47, p. 605.

Host and record of specimens.—EHight females were obtained from the gills of Oncorhynchus nerka at
Big Payette Lake, Idaho, June, 1914, and were sent to the auther from the United States Bureau of
Fisheries. They have received catalogue no. 43563, U. S. National Museum, and since Ddna’s original
specimens have been lost they will serve as surrogate types of the species.

Specific characters of female.—Dana’s original description and figures were excellent as far as they
went, but he included only the general body characters and no appendages were mentioned except the
second maxille.

These new specimens show a wider and shorter body, strongly flattened on the ventral surface, and in
the larger females showing distinct ventral grooves of segmentation. The cephalothorax is inclined
nearly at right angles to the trunk; the contour of its dorsal surface is clearly shown in figure 77 and is
very different from that of any other species of the genus, approaching most closely that of salmonea.

The first antennz are very short, apparently three-jointed, and tipped with a minute spine; the
second antennz are long and stout, the basal portion two-jointed, the rami one-jointed and about the
same size, the exopod tipped with a fairly large chela, the endopod with two or three small spines; on
the ventral surface of the exopod near the base of the chela is a peculiar compound spine. The mandi-
bles are long and slender, with strongly hooked teeth; the first maxillz are short, somewhat swollen at
the center, and end in three small spines of about the same size; the second maxillz in younger speci-
mens are smooth and longer than the trunk, in older females much wrinkled and shorter than the trunk.
The maxillipeds are large and stout, the basal joint considerably swollen and armed on its inner margin

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 363

near the distal end with a small papilla like those in other species; the terminal joint is slender and is
tipped with a larger and a smaller claw, somewhat like a chela.

Total length (larger specimens), 4.40 mm.; cephalothorax, 1.60 mm. long, 2.40 mm. wide; trunk,
2.75 mm. long, 3.30mm. wide. Eggstrings, 5.4omm. long, 1.25 mm. wide. Bullaz.6s mm. in diameter.

Remarks.—It is gratifying to obtain new specimens of Dana’s species, probably from the same host.
They confirm his description in all its essential features and enable us to supply the details of the
appendages which were lacking. They also establish the species beyond any doubt, as is shown by the
dorsal contour of the cephalothorax, the general body form and proportions, and the details of the man-
dibles, second antenne, and first maxille.

Salmincola siscowet (Smith).

Lerneopodua siscowet Smith, Report U. S. Commissioner Fish and Fisheries for 1872-73, pt. 2, p. 664, pl. 3, fig. 15, 16; Wilson,
Proc. U. S. Nat. Mus., vol. 47, p. 608, pl. 30, fig. 23-29.

Host and record of specimens.—Seven females were taken from the gills of Cristivomer namaycush
siscowet at Outer Island, Lake Superior, by J. W. Milner; they are numbered 39597, U. S. National
Museum.

Salmincola edwardsii (Olsson).

Lerneopoda edwardsii Fasten, Report Wisconsin Commissioners of Fisheries for 1911-12, p. 11, 4 unnumbered plates; Biol
Bull., vol. 27, p. 116, pl. 1-3.
Salmincola edwardsii Wilson, Proc. U. S. Nat. Mus., vol. 47, p. 609, pl. 30, fig. 30-35.

Host and record of specimens.—Twenty-five females (catalogue no. 43574, U. S. National Museum)
from gills of brook trout, Salvelinus fontinalis, at Wild Rose, Wis. Others have been obtained from the
same host at Caledonia, N. Y.; Houghton, Mich.; Northville, Mich.; St. Paul, Minn.

Remarks.—This species often causes serious trouble in fish hatcheries, loading the gills of the trout
until they are suffocated and large numbers of them perish. Each of the lots mentioned above have
come from hatcheries thus afflicted, and Fasten’s first paper gives an excellent account of the disease
produced in brook trout by this parasite.

Salmincola oquassa Wilson.

Salmincola oquassa Wilson, Proc. U.S. Nat. Mus., vol. 47, p. 611, pl. 31, fig. 36-40.

Host and record of specimens.—Five females were obtained from the blueback trout, Salvelinus
oquassa, at Rangely Lakes, Me., November 27, 1884; they have received catalogue no. 39604, U. S.
National Museum.

Salmincola bicauliculata (Wilson).

Lerneopoda bicauliculata Wilson, Proc. U. S. Nat. Mus., vol. 35, p. 472, pl. 82.
Salmincola bicauliculata Wilson, idem, vol. 47, p. 612, pl. 31, fig. 41, 42.

Host and record of specimens.—A single female was taken from a ‘‘trout’’ at Mapleton, Oreg., by
Dr. S. E. Meek in 1896 and has received catalogue no. 38575, U. S. National Museum.

Salmincola falculata (Wilson).

Lerneopoda falculata Wilson, Proc. U. S. Nat. Mus., vol. 35, p. 473, pl. 83.
Salmincola falculata Wilson, idem, vol. 47, p. 613, pl. 31, fig. 43, 44.

Host and record of specimens.—Four females from the gills of Oncorhynchus nerka at Baker Lake,
Wash., in rgo2, catalogue no. 38586, U. S. National Museum. Three other lots were obtained by the
Bureau of Fisheries from trout in California, catalogue no. 38588, 38589, 38590, U. S. National Museum.

Salmincola inermis (Wilson).

Lerneopoda inermis Wilson, Proc. U. S. Nat. Mus., vol. 39, p. 632, pl. 68.
Salmincola inermis Wilson, idem, vol. 47, p. 614, pl. 32, fig. 47-51.

Host and record of specimens.—This species has been found abundantly upon the lake herring,
Argyrosomus artedi, in Lakes Huron and Superior and in rivers running into them.

Salmincola beani (Wilson).

Lerneopoda beani Wilson, Proc. U. S. Nat. Mus., vol. 35, p. 470, pl. 8.
Salmincola beani Wilson, idem, vol. 47, p. 615, pl. 32, fig. 52, 53.

Host and record of specimens.—Found in considerable numbers on the gills of the quinnat salmon,
Oncorhynchus tschawytscha, in McCloud River, Cal., and at Battle Creek, Colo.

364 BULLETIN OF THE BUREAU OF FISHERIES.

Salmincola carpenteri (Packard).

Achtheres carpenterit Packard, Annual Report U.S. Geol. and Geog. Survey of the Territories for 1873, p. 612, 1 text figure.

Salmincola carpenteri Wilson, Proc. U.S. Nat. Mus., vol. 47, p. 616, pl. 33, fig. 54-60.

Host and record of specimens.—From the gills of ‘‘trout’’ in a tributary of the East River, Colo., and
from ‘“‘salmon’’ at Battle Creek, Colo.; the former host has been identified by R. R. Gurley as Salmo
mykiss.

Remarks.—Neither this nor any of the other species of the genus have ever been found associated
with any glochidium, but not because the two are uncongenial. Very few, if any, of the species of
trout and salmon have been examined for glochidia, because usually the streams and lakes in which
they live are inhabited by only a few mussels, none of which are of any value commercially. Further-
more, neither of the two kinds of fish are found in those localities where artificial infection has been
tried, and thus there has been no chance to ascertain whether they will take the glochidia or not. But
the susceptibility of these fish to copepod parasites would lead us to suppose that they would make
good hosts for glochidia. In all probability future examination will discover glochidia upon some of
them, and if artificial propagation is tried in lakes as well as rivers there would seem to be no reason
why these fish could not be used as carriers for the glochidia.

Achtheres pimelodi Krgyer. (Pl. Lxx1.)
Achtheres pimelodi Krdéyer, Naturhistorisk Tidsskrift, 3 Raekke, 2 bd., p. 272, pl. 17, fig. 5a, 5b; Wilson, Proc. U. S. Nat.
Mus., vol. 47, p. 628, pl. 38.

Host and record of specimens.—Both sexes have been obtained from the gill arches of various catfish;
from Ictalurus punctatus at Cincinnati, Ohio; from Ameiurus nebulosus at Put-in Bay, Ohio; from Ictalu-
rus anguilla and Leptops olivaris at Fairport, Iowa. From the former of the last two a female was
obtained and numbered 47726, U. S. National Museum; from the latter a female with ripe eggs, which
has been given catalogue no. 47771, U.S. National Museum,

First copepodid larva.—The egg strings of the ripe female just mentioned were detached and the larve
hatched out in an aquarium, August 22, 1914. These larve differed in several important particulars
from those of ambloplitis already described (Proceedings U. S. National Museum, vol. 39, p. 208), as
may be seen by the following:

Cephalothorax elliptical, the breadth to the length as 11 to 17, not enlarged anteriorly over the base
of the second antennz; head separated from the first thorax segment by lateral notches, but without a
well-defined groove; posterior lobes large and evenly rounded. Attachment end of the filament excep-
tionally large, somewhat quadrate in dorsal view, and close to the frontal margin; coiled portion of the
filament also unusually long and situated far back in the cephalothorax. Dorsal color patch about the
same size as the attachment end of the filament, shield-shaped, and placed nearly at the center of the
cephalothorax. Posterior portion of the body made up of four segments, all the same width, but dimin-
ishing in length backwards, the fourth one about one-third the length of the first, which latter carries
on its sides, the rudiments of a third pair of swimming legs. Anal laminze twice the length and more
than half the width of the last segment, so that they overlap on the midline, each armed with two large
sword-shaped, jointed sete on the inner side and three shorter ordinary ones on the outer margin.

First antenne four-jointed and heavily armed with sete; second antenne similar to those in amblo-
plitis; mandibles short and thickset, made up of a single spherical joint tipped with a stout spine and
carrying a triangular palp on the outer margin. First maxilla two-jointed, the basal joint spherical,
the terminal one long and pointed; second maxille with a strongly swollen, almost spherical basal joint
and a stout terminal claw, bent at right angles near its center; maxillipeds comparatively slender, with
two unarmed joints and a stout curved claw. Swimming legs similar in all respects to those of amblo-
plitis, biramose, each ramus one-jointed, the exopods tipped with four plumose sete, the endopods
with six.

Total length, 0.45 mm.; width of cephalothorax, 0.20 mm.

Remarks.—The most noticeable differences between the present larva and that of ambloplitis are
the lack of separation of the first thorax segment, the comparatively enormous attachment filament, the
swordlike setz on the anal lamine, and the bulky, swollen form of the mandibles, first and second
maxillz. In the present larva also the mandibles have a rudimentary palp while the first maxillz
have none, the reverse being the case in ambloplitis. There are four patches of pigment, but the dorsal
patch and the posterior ventral one are relatively much larger than the others, which are reduced to
minute spots.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES 365

Achtheres corpulentus Kellicott.
Achtheres corpulentus Kellicott, Proc. American Soc. Microscopists, vol. 1, p. 54, pl. 1, fig. 1-3; Wilson, Proc. U. S. Nat.
Mus., vol. 47, p. 619.
Host and record of specimens.—This species has been obtained from Avgyrosomus artedi in Buffalo
Harbor and Niagara River; from A. prognathus in Lake Ontario and Lake Michigan; from A. hoyi in
Lake Michigan; and from Coregonus clupeiformis in Lake Erie.

Achtheres micropteri Wright.
Achtheres micropteri Wright, Proc. Canadian Institute, n.s., vol. 1, p. 249, pl. 2, fig. 1-11; Wilson, Proc. U. S. Nat. Mus.,
vol. 47, p. 620, pl. 34.

Host and record of specimens.—Found by Wright on the smallmouth black bass near Toronto, Canada,
and by the present author on the same host in the Kankakee River, Ind.; also found upon the large-
mouth black bass in the Kankakee River and at Lake Maxinkuckee, Ind., and at Constantia, N. Y.

Remarks.—On the gills of the largemouth bass this species, together with Ergasilus centrarchidarum,
is often associated with glochidia of the Lampsilis group. Thus far none of these glochidia have been
found on the gills of the smallmouth bass, but since both of the copepod parasites are found there it is
reasonable to believe that future search will reveal some of the glochidia. Atall events, the presence of
the copepods shows that both bass are good subjects for artificial infection.

Achtheres lace Kroyer.
Achtheres lace Krgyer, Naturhistorisk Tidsskrift, 3 Raekke, 2 bd., p. 348, pl. 17, fig. 6; Wilson, Proc. U. S. Nat. Mus., vol.
47, D. 622, pl. 35.

Host and record of specimens.—Found originally by Kr@yer in the mouth of a North American perch,
which he called “ Perca laca,’’ probably P. flavescens. Eight females were obtained from the gills of the
striped bass, Roccus lineatus, in the Potomac River near Washington, D. C.

Remarks.—lf Kr@yer’s specimens really came from P. flavescens, they were strictly fresh-water
species; the striped bass, on the other hand, goes back and forth from fresh to salt water. This fact of
course would make it of no use as a carrier of glochidia; none have ever been found upon its gills nor are
they likely to be in the future.

Achtheres coregoni (S. I. Smith).

Lerneopoda coregoni Smith, Report U. S. Commissioner Fish and Fisheries for 1872-73, pt. 2, p. 664, pl. 3, fig. 17.

Achtheres coregoni Wilson, Proc. U. S. Nat. Mus., vol. 47, p. 623, pl. 36.

Host and record of specimens.—This species has been found upon the whitefish, Coregonus clupei-
formis, in Lake Michigan, upon Argyrosomus artedi in the Niagara River, and upon A. hoyi in Lake
Michigan. It has not yet been associated with any glochidium.

Achtheres ambloplitis Kellicott.

Achtheres ambloplitis Kellicott, Proc. American Soc. Microscopists, vol. 1, p. 56, pl. 3, fig. 6, 7; Wilson, Proc. U. S. Nat.

Mus., vol. 47, p. 626. 1

Host and record of specimens.—Found on the red-eye, Ambloplites rupestris, at Lake Maxinkuckee,
Ind., and in the Shiawassee River, Mich., and upon “redfish’’ at Big Payette Lake, Idaho.

Remarks.—This species is associated with Lampsilis glochidia on the gills of the red-eye, and its
presence indicates that these fish are good hosts for artificial infection, as has been proved by actual
experiments.

LERNAID.

Lernezocera variabilis, new species. (Pl. Lxxm.)

Host and record of specimens.—Ten females were obtained from the scales and flesh of Lepomis
pallidus in Whisky Slew, Fairport, Iowa, July 10, 1912, and have received catalogue no. 47727, U.S.
National Museum; fifteen females were obtained from the same host in the Mississippi River at Fairport,
July 25, 1912, and have received catalogue no. 47738, U. S. National Museum; six females from the
same host in McPhersons Slew, Fairport, August 8, 1912, catalogue no. 47739, U. S. National Museum;
eight copepodid larve from the gill filaments of the short-nosed gar, Lepisosteus platostomus, in ‘“‘Sun-
fish Lake,’’ Fairport, July 24, 1914, catalogue no. 47740, U. S. National Museum; five copepodid larve
from gill filaments of the sauger, Stizostedion canadense, in Whisky Slew, Fairport, August 12, 1914,
catalogue no. 47741, U. S. National Museum; four copepodid larve from gill filaments of sauger in Dark

366 BULLETIN OF THE BUREAU OF FISHERIES.

Slew, Fairport, August 14, 1914, catalogue no. 47742, U. S. National Museum; three copepodid larve
from gill filaments of sauger in Lake Pepin, Mississippi River, August 28, 1914, catalogue no. 47743,
U.S. National Museum. One or two copepodid larve were also obtained from the gills of the bullhead,
Ameiurus melas, in ‘‘ Sunfish Lake,’”’ August 20, 1914; these were preserved and used for sectioning.

Specific characters of female.—Body club-shaped, enlarged two or three diameters posteriorly; horns
varying in number, size, and arrangement; usually they are four in number, short and very wide and
strongly flattened dorso-ventrally, so that they become thin lamin; the four are arranged in pairs,
attached to the sides of the thorax, behind the head, the first pair just in front of the first swimming
legs, the posterior pair just in front of the second legs; they are all about the same size, nearly as wide
as long, and each is attached separately to the thorax and extends out nearly at right angles to the long
axis of the body. Sometimes the two anterior horns are much larger than the posterior ones (fig. go)
and are turned forward like a large horseshoe, whose sides are parallel to the body axis; sometimes the
two posterior horns are more or less fused into a single one, much smaller than the lateral anterior ones.
Instead of being buried in the flesh these horns are often applied to the surface of the scales (fig. 92),
with whose substance they apparently fuse quite solidly, so as to furnish a secure attachment.

The body is segmented and the diameter posteriorly is three times that anteriorly; at the posterior
end there is a small lateral tubercle on either side, ventral to the egg string, and a much larger median
dorsal tubercle, the abdomen, which reaches far behind the lateral ones; the anal papillz are compara-
tively large and jointed, and each carries three or four small sete around the base in addition to the
large terminal one. .

The egg strings are narrow and elongate, less than a third the length and width of the body.

Head elliptical, a little longer than wide, without an anterior rostrum; first antenne three-jointed,
the two basal joints considerably longer and wider than the terminal one, and all of them heavily armed
with sete; second antennz two-jointed, the terminal joint half as long again as the basal and ending in
a single large claw and a tuft of sete, the basal joint unarmed. Mandible a single slender curved claw
mounted on a stout hemispherical base inside the lips; first maxilla a very much stouter claw, curved
abruptly near the base and bluntly rounded at the tip; second maxilla armed with the usual two stout
claws, also abruptly curved, but nearer the tip, which is much sharper than in the first maxilla.

Maxilliped comparatively large and stout, tipped with five strong curved claws, with a large blunt
knob at their base and a medium-sized papilla on the inner margin, tipped with a single seta.

Color a dark creamy white.

Body length (excluding horns and egg strings), 6 mm.; greatest diameter, 1 mm. Length of egg
strings, 3 mm.; diameter of same, 0.36 mm.

(variabilis, variable, alluding to the size, number, and position of the cephalic horns.)

Remarks.—This species is chiefly characterized by the four flattened horns, which are entirely
separated to their base and which are often attached to the surface of a scale instead of being buried in
the flesh. The antennz are also quite different from those of other species.

The discovery of the copepodid larve upon the gills of the sauger, the catfish, and the short-nosed
gar serves to associate this species, and presumably the others also, with gill glochidia. These larve
are very similar to an adult ergasilid but are smaller and of course without egg strings. They are very
lively and loosen their hold (which is made by means of the curved claws on the second antennz) on
the gill filament at the slightest provocation and dart around over the gills rapidly, taking a new hold
somewhere else. For this reason they would probably offer more hindrance to the attachment of the
mussel glochidia than the sluggish ergasilids. At the same time the hindrance would be only tempo-
rary, since these are larve whose transformation only requires a brief period for its accomplishment,
after which they leave the gills and fasten themselves elsewhere upon the body of a new host.

Lernezocera tenuis, new species. (Pl. Lxxiu, fig. 102-107.)

Host and record of specimens.—A single female was taken from the side of the body of a sheepshead,
Aplodinotus grunniens, at Fairport, July 16, 1914; it becomes the type of the new species and has been
given catalogue no. 47737, U. S. National Museum.

Specific characters of female—Body long and slender with very little posterior enlargement; a single
horn on either side of the head attached farther back than in other species, extending out at right angles
to the body axis, and divided into two branches, the dorsal of which is much larger and nearly four
times as long as the ventral; both branches are somewhat enlarged and bluntly rounded at the tip.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 367

Behind the head the body narrows for a short distance, then widens gradually, and there is no abrupt
posterior enlargement. At the posterior end on either side above the base of the egg string is a small
tubercle which is single and does not project much from the body; the dorsal median tubercle, the
abdomen, is considerably larger than the lateral ones and terminates in the usual anal papilla. Each
egg string is half the length of the body and four-fifths the width and tapers posteriorly to a narrow
rounded point; the eggs are minute and there are about 150 in a string.

The head is circular in outline and a little wider than long; first antenne three-jointed, joints
diminishing a little in length and diameter from the base outward and heavily armed with sete; second
antenne two-jointed, joints the same length, the basal one unarmed, the terminal one with the usual
armature of stout curved claw and sete. Second maxille as large as the maxillipeds, with stout ter-
minal claws; maxillipeds short and thickset, each with four terminal claws, a small knob at their base
and a minute process on the inner margin.

Color (preserved material), a grayish white.

Body length (excluding the horns and egg strings), 9.60 mm.; greatest diameter, 0.60 mm.; trans-
verse length of both horns and head, 5.66 mm. Length of egg strings, 4.25 mm.

(tenuis, slender, alluding to the body as a whole.)

Remarks.—This species may be recognized by the fact that its horns stand out at right angles to
the body axis and are cylindrical instead of flattened; its body is not enlarged posteriorly, and the egg
strings are very long and slender. It does not appear to be common, since only a single specimen has
thus far been found, and it is not known to be associated with any glochidium.

Lernzocera cruciata Le Sueur. (Pl. Lxxm, fig. 108, 109; Pl. Lxxtv, fig. r1o.)
Lerneocera cruciata Le Sueur, 1824, Jour. Acad. Nat. Sci. Philadelphia, vol. 3, p. 286, pl. 2; Kellicott, 1880, Proc. Amer.
Soc. Microscopists, vol. 1, p. 64, pl. 1, fig. x.

Host and record of spectmens.—This species was originally reported by Le Sueur from the “rock bass,
Cichla enea”’ (Ambloplites rupestris) of Lake Erie. Kellicott’s specimens were taken from “rock bass
in the Shiawassee River, the Upper Saginaw, at Corunna, Mich., about 25 per cent of the fish being
parasitized. * * * They are taken occasionally from the Niagara at Buffalo.’’ (p. 68.) Gurley in
his manuscript identified this species from the following hosts and localities: On rock bass from Lake
Erie at Erie, Pa., June 21, 1894; from the Sandusky River at Fremont, Ohio; and from Fox Creek (tribu-
tary of the Detroit River) at Detroit, Mich., the latter on August 22, 1894 (collector, Cloudsley Rutter).
On the sunfish, Eupomotis gibbosus, from Cattaraugus Creek (tributary of Lake Erie) at Gowanda,
N. Y., August 17, 1893; from Elk Creek, Girard County, Pa., August 3, 1893; and from the Maumee
River at Perrysburg, Ohio. On the redhorse, Moxostoma macrolepidotum duquesnei, from Maple River
in Cass County, N. Dak. Gurley adds: “It should further be noted that the specimen in question is
clearly L. cruciata and not Krfyer’s L. catostomi, which also infests the redhorse.’’

Three lots of specimens were taken from the flesh along the sides of the body of the largemouth
black bass, Micropterus salmoides; 10 females from Black Creek, N. C., catalogue no. 42306, U. S. National
Museum; 7 females from Crooked S Slew, Fairport, Iowa, catalogue no. 47728, U. S. National Museum;
5 females from Scott, Lonoke County, Ark., catalogue no. 47729, U. S. National Museum.

Specific characters of female.—Body club-shaped, rather slender toward the head, gradually increas-
ing in diameter posteriorly and terminating in a sudden enlargement at the posterior end. From either
side of the cephalothorax extends a stout horn, chitinous in texture, which immediately divides into two
conical branches, one of which is turned forward and the other backward at varying angles. The basal
portion of each horn is short and very broad, while the base of the posterior branck is often twice the
diameter of the anterior. Body obscurely segmented, with a large double tubercle on either side at
the posterior end, the median dorsal tubercle, the abdomen, being still larger though single and termi-
nating in two small anal papille, each armed with two or three sete. Egg strings conical, the base
attached to the body, the pointed end free, one-third as wide as long; eggs small, not arranged in rows,
about roo in each string.

Head one-quarter wider than long, with a narrow rostrum projecting from the center of the anterior
margin; first antenne four-jointed, the basal joint the shortest, the next joint the longest, all the joints
heavily armed with sete; second antenne two-jointed, joints about the same length, the basal one
unarmed, the terminal one ending in two curved claws, two long sete and a shorter one, with four minute
spines along the inner margin.

368 BULLETIN OF THE BUREAU OF FISHERIES

First maxilla ending in a single claw; second maxilla with two claws of the same size; maxillipeds
two-jointed, the basal joint unarmed, the terminal joint ending in five curved claws, at the base of which
is a large rounded knob, and back of the knob on the inner margin a tiny process terminated by a single
spine. The bases of the maxillipeds are so far behind the mouth tube that their tips do not quite reach
the bases of the second maxille.

Color of young specimens a uniform creamy white, turning more or less dark reddish brown with
age, the tips and sometimes the entire branches of the cephalic horns dark brown, almost black.

Body length (excluding horns and egg strings), 8 mm.; greatest diameter, 0.70 mm.; diameter of
posterior enlargement, 1.40 mm. Length of egg strings, 2.10 mm.; greatest diameter of same, 0.70 mm.

(cruciata, torturing or tormenting.)

Remarks.—The parasite is usually attached nearer the head than the tail of the fish; the head, horns,
and one-third of the body are buried in the flesh, usually beneath a scale or in the angle between two
scales, and in such a way that the posterior two-thirds of the body points diagonally backward, and
when the fish is in motion hangs close to the body of the latter. This species is associated with the
glochidia of Anodonta corpulenta upon the largemouth black bass, and suggests that these external glo-
chidia will subsequently be found also upon the other fish which serve as Hosts for this Lerneoceran.

Lernzocera tortua Kellicott. (Pl. Lxxiv, fig. 111-113.)

Lerneocera tortua Kellicott, 1881, Proc. Amer. Soc. Microscopists, vol. 2, p. 41, 1 unnumbered plate.

Host and record of specimens.—Originally obtained by Kellicott from Grindstone Creek, a tributary
of Lake Ontario, in July, 1880. Each Lerneocera was deeply buried in a tumor caused by its presence
just behind, or in the axilla of, a pectoral fin of ‘‘Ameiurus catus Gill.’’ According to Dr. B. W. Ever-
mann A. catus does not occur in Lake Ontario, the forms found there and usually referred to it being
either melas or nebulosus, in this instance more probably the latter. Seven females were taken from
A. nebulosus at Thomaston, Ga., by B. B. White and have been given catalogue no. 12030, U. S. National
Museum. A single female was taken from Ictalurus furcatus at Fairport, Iowa, June 2, 1910, and has
received catalogue no. 47772, U. S. National Museum.

Specific characters of the female.—Body straight and somewhat enlarged posteriorly; a lateral horn on
either side of the cephalothorax, dichotomously branched, tuberculated, and standing out from the
head at right angles to the body axis, so that the two horns are in the same straight line; a single dorsal
horn, forked at the apex; all three horns strongly flattened anteroposteriorly and half as wide as long.
In the Iowa specimen the horns are flattened, but the branches are much smaller and more slender
than those of the Georgia specimens. Body sometimes obscurely segmented, with no lateral tubercles
at the posterior end; the median dorsal tubercle or abdomen comparatively long and three-quarters of
the diameter of the body; anal papille large and well armed with plumose sete; egg strings moderately
long (one-third the length of the body) and subcylindrical, tapering posteriorly.

Head ovate, considerably longer than wide; first antenne four-jointed, the three distal joints about
the same length, the proximal joint shorter; second antenne three-jointed, the two distal joints about
the same length, the proximal one much shorter; the terminal joint is enlarged and tipped with a long
curved claw and several curved sete; second maxilla comparatively stout, each terminating in two
large curved claws; maxillipeds rather short and stout, the terminal joint much narrower than the
basal and ending in four or five slender claws, with a large knob at their base, but no papilla on the inner
margin.

The two lateral cephalic horns are united across the front of the head and the ridge thus formed
projects a long ways ventrally, owing to the anteroposterior flattening of the horns. On the ventral edge
of the ridge, or a little removed from it on the posterior surface, is the first pair of swimming legs.

Color (preserved material), a rich reddish brown.

Body length (excluding horns and egg strings), 11.25 mm.; greatest diameter, 0.75 mm.; combined
length of lateral horns, 3.90 mm. Length of egg strings, 4 mm.

Remarks.—The foregoing description and the accompanying figures agree fully with those given
by Kellicott, except in the position of the fourth swimming legs (see p. 111). In all the specimens
obtained at Thomaston, Ga., the fourth legs are relatively much nearer the posterior end of the body
than is represented by Kellicott, and there is no indication of another groove posterior to them or between
them and the third pair. This species does not seem very widely distributed nor very abundant in any

locality. While its hosts are common in the Mississippi River, only a single specimen of the parasite
has thus far been found.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 369

Lernzocera catostomi Krgyer.

Lerneocera catostomi Kryer, 1863, Naturhistorisk Tidsskrift, vol. 2, p. 321, pl. 18, fig. 4, ae.

Host and record of specimens.—Two females were found by Krg¢yer upon a Moxostoma macrolepidotum
duquesnii from the Mississippi River near St. Louis, Mo. None have been found since and the original
specimens are probably lost, so that we are compelled to rely wholly upon Krgyer’s description and
figures, which may be summed up as follows:

Specific characters of female.—Body long and club-shaped, enlarged two or three diameters posteri-
orly; a short horn on either side of the cephalothorax, flattened anteroposteriorly and cleft at the tip;
a similar median dorsal horn. Body segments indistinct; lateral tubercles at the posterior end poorly
defined, median dorsal tubercle, the abdomen, but little longer and comparatively wide; egg strings
narrow and elongate.

Head circular in outline, with a small broadly obtuse rostrum on the anterior border; first antennz
three-jointed and heavily armed with sete; second antenne two-jointed, the basal joint long and linear,
the terminal joint small, oval, and armed with small sete and spines; maxillipeds with a swollen basal
joint and an oval terminal joint, tipped with four large and strong claws, gradually increasing in size,
the outermost one as long as the segment; knob at the base of these claws small, papilla on the inner
margin also small and tipped with a single spine.

Color, a uniform whitish yellow.

Body length (excluding horns and egg strings), 8 mm.; greatest diameter, 1.35 mm.

Remarks.—Neither of Krgyer’s specimens had complete egg strings, so that their length can not
be given, but the remnant left on one of the females indicated that they were long and narrow and the
eggs were small. The species is readily distinguished from cructata, which is found on the same host
by the fact that it has three horns instead of two. From fortua it may be distinguished by the smaller
size of the horns and the larger size of the abdomen and by the details of the antenne and maxillipeds.

Lernzocera pomotidis Krdyer. (Pl. Lxxiv, fig. 114-118.)

Lerneocera pomotidis Krfyer, 1863, Naturhistorisk Tidsskrift, vol. 2, p. 323, pl. 1s, fig. 5, a-h.

Host and record of spectmens.—Six or seven females were originally obtained by K¢ryer from the gills
of a “‘Pomotis’’ species near New Orleans. These are the types of the species and if extant are in the
Royal Museum at Copenhagen. A single female was taken from the gill cavity of the bluegill, Lepomis
pallidus, at Fairport, August 29, 1914. It has received catalogue no. 47773, U.S. National Museum,
and will serve as a surrogate type of the species if the original specimens are no longer in existence.

Specific characters of the species.—Body long and slender, only slightly enlarged posteriorly; a horn
on either side of the cephalothorax, divided into two branches which are longer than those in cruciata,
more slender, and more nearly parallel with the long axis of the body; each horn is two-fifths the entire
length of the body and about the same diameter as the anterior portion of the thorax. Body obscurely
segmented, the lateral tubercles at the posterior end large, distinct, and with a slight emargination at
the center; the median dorsal tubercle, the abdomen, heart-shaped and but a trifle longer than the
lateral ones; egg strings narrow and elongate.

Head circular in outline, about the same length and width and without any anterior rostrum; first
antenne four-jointed, the three terminal joints the same length and well armed with sete, the basal one
shorter and unarmed; the terminal joint carries at its tip two curved claws, similar to those on the second
antenne; the latter are two-jointed, the terminal joint considerably longer than the basal and more slen-
der; second maxille small with slender terminal claws; maxillipeds also small and slender, two-jointed,
and terminating in three claws, with no knob at their base but with a large process on the inner margin,
tipped with a tiny spine; these maxillipeds do not quite reach the posterior border of the maxille.

Color a uniform creamy white.

Total length (excluding horns and egg strings), 10.45 mm.; greatest diameter, 0.50 mm.; length of
horns, 4.20 mm.

Remarks.—This is undoubtedly the same as Krdéyer’s specimens and shows that the species is not
confined to the lower part of the river nor to one host, but is likely to be found elsewhere. The present
host is one of the sunfishes and is closely related to Kréyer’s “‘ Pomotis sp.,’’ and may even possibly be
identical with it. The species may be distinguished by the long, sharp, and slender horns and by the
fact that the body has almost no posterior enlargement. It is also worth special notice that it is found
on the gills or in the gill cavity and not on the outside of the body. It is not well enough known as
yet for it to be associated with any glochidium.

370 BULLETIN OF THE BUREAU OF FISHERIES.

Lerneocera pectoralis Kellicott.

Lerneocera pectoralis Kellicott, 1882, Proc. Amer. Soc. Microscopists, vol. 4, D. 77.

Host and record of specimens.—A dozen females were obtained from the red-finned shiner, Notropis
cornutus, in the Shiawassee River at Corunna, Mich., in July and August, 1881. They were fastened
to reddish lumps in the axils of the pectoral fins. None of these original specimens have been preserved
and no others have been obtained, so that Kellicott’s description gives us all the knowledge we possess
of the species; he published no figures.

Specific characters of female.—Body strongly bent and club-shaped; three horns on the cephalo-
thorax, the two lateral ones three or four pronged, the dorsal one stout and forked at the apex. Body
indistinctly segmented; the lateral tubercles at the posterior end small, the median dorsal tubercle,
the abdomen, much longer and wider, and extending far over the bases of the ovisacs; the latter are
short and club-shaped.

Total length, 7.50 mm.; width of horns, 1.70 mm.

Remarks.—This species resembles L. tortua but is little more than half as long, the dorsal horn is
forked, the egg strings are shorter and club-shaped, and the terminal sete on the anal papille are not
plumose.

None of these species of Lerngocera are as yet well enough known to enable us to
establish their relations with the mussel glochidia. Whatever may be the relations of
the adult fastened in the flesh of its host to the mussel glochidia on the fins, it is reason-
ably certain that the copepodid larvee of the various species of Lerneocera are much more
closely related to the glochidia on the gills. Before we can understand this relation
thoroughly, there must be considerable more research and observation on the genus.

To facilitate the distinctions between the different species, the following table may
be presented; in it the entire length of the parasite is taken as 100 units, and the distance
of the four pairs of swimming legs from the anterior border of the head (excluding the
horns) is given in percentages of 100.

Species. 1 leg. 2 legs. 3 legs. 4 legs.
West ahs aire aise goo bad ote Sica open nie in. CoG sithwist overt fein ofs Patera alayehevcreerelauejeraate teraetorsiaceateroietey a 4 8.3 30 7°
CTTTCh TR ne Os See eC Te GUE Aan ORC Ge aA hope bero Gob cacdn SC OaGaLC 764 II 35 7°
bt Ta) 3 0 7: pee ena a Be Oe Pe Rn On ci entrar Gis CORPO BCE a onacRaaAC sano nears 5-4 7 30 70
nt 20 1 C} Sen POR an Ber BOR RuOnn ae HAC rGe tu 200 DOTeneDo Ie COs anor oO bODooUm ON adaus bos 12 38 52 88
(ere (al dee BE Sant Gone quOnmao ro Oc BOUnT a GAD On OUC On OnadoEManogOedeGouDON. Io 15 42 15
Catostorrada cs. cco.5 oe ok ccsieteees Shel io rerela aid a DG a eheredere sas cla he wearer aia a'ofeteve oe bletarere arepehoyar are RehaeS 4 8 48

It is almost certain that the absolute distances vary in the same species with the
development of the individual; the older the parasite becomes the farther removed are
the legs from the head; but the relative distance of the pairs one from another ought
not to vary much, and it is these relative distances that are expressed in the above table.

The male does not develop beyond the fourth copepodid stage and never attaches
itself to the flesh of a fish nor to the body of the female, but after the mating of the
sexes the male dies. This makes it necessary to secure the male from the tow or from
the gills of some fish prior to the mating, by no means an easy task; but these males
and the copepodid stages of the females furnish the data which will eventually decide the
validity of the various species, as well as their economic relations.

GENERAL REMARKS.

In a recent paper by Dr. W. A. Cunnington, which is a report on the parasitic
Eucopepoda and forms part of the “Zoological Results of the Third Tanganyika Expe-
dition,’’* he says: “It is clear that whatever may be the case for marine fishes, the fishes

@ Proceedings Zool. Soc. London, 1914, p. 819-829, pl. r.

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 371

of fresh water are relatively seldom the prey of parasitic Eucopepoda under natural
conditions” (p. 828’. And he adds: “‘A study of the literature of the subject confirms
our conclusion.”’

His judgment is based upon the results of this African expedition, during which he
says very large numbers of fish were examined, but only two of them were found infested
with eucopepods.

While such a conclusion seems inevitable from the data he has given, it must be
understood as applying to Africa, and perhaps to that portion covered by these Tan-
ganyika expeditions and not to the world at large. There has been very little work
done on the parasites of fresh-water fishes, as has been already shown (p. 333), and no
one can say what the future holds in store. It is possible that other portions of Africa
are richer in these parasites, and it is certain that the results of the present investigation
are not essentially inferior to those obtained from salt-water fishes. It has already been
stated (p. 341) that a fish’s efficiency as a host may be measured either by the number
of any single parasite it harbors or by the variety of species. If we are comparing
fresh-water fish with salt-water fish, or the fish from one region in the world with those
from another region, we should take into account both the number and the variety.
In variety of forms the salt-water fish considerably surpass those from fresh water, but
in number of specimens the latter sometimes surpass the former. The present author
never has obtained any salt-water fish that could compare with the two crappies in
numbers of parasites. Furthermore, in the variety of species found upon any single
kind of fish the fresh-water fish present an average fairly comparable with those from salt
water. Three and four from the same fish are the general rule rather than the exception.
(See table, p. 338.)

And if we were to include the mussel glochidia and all other kinds of gill parasites
with the copepods, the salt-water fish would be hard pushed for a victory. Not many
salt-water fish can compare with the crappie (P. annularis), which harbors 13 species of
glochidia, 3 species of copepods, and 3 species of trematode ectoparasites, 19 in all; or
with the sheepshead, which acts as the host of 11 species of glochidia, 2 species of trema-
todes, and two of copepods, 15 in all; or with the sauger, upon which have been found
6 species of glochidia, 2 species of trematodes, and 4 species of copepods, 12 inall. And
it must be remembered that these are all natural infestations, which have occurred under
perfectly ‘normal conditions. When we come to the abnormal conditions which are
favorable to the copepod parasites, then their numbers increase to such a degree that
they cause serious epidemics in the breeding ponds and often kill off large numbers of
the fish; and since it is fresh-water fish only that are bred in this way it follows that
this sort of damage is confined to them and does not occur amongst salt-water fish.

The facts presented in the present paper open up a very fascinating chapter in the
book of copepod parasitology, and one that bids fair to become far-reaching in its prac-
tical relations; but it must be remembered that we have as yet scarcely made a begin-
ning, and that a vast amount of work is still to be done before we can reach a final solu-
tion of the problems. From the facts here presented, however, it would seem as if fresh
water presented fully as rich a field to the parasitologist as can be found in the ocean.

Fic
Fic
Fic
Fic

EXPLANATION OF PLATES.

PLATE LX.

Female of Argulus canadensis.

. 1. Dorsal view. Fic. 5. Maxilliped.

. 2. Respiratory areas. Fic. 6. Basal joints of fourth leg.
. 3. First and second antennz.

. 4. Chitin ribs supporting the margin of the

sucking disks. |

PLATE LXI.

Females of Argulus flavescens and A. mississippiensis.

Fic. 7. Dorsal view of A. flavescens. Fic. 12. Basal joints of fourth swimming leg.
Fic. 8. Respiratory areas. Fic. 13. Chitin ribs of sucking disk of A. missis-
Fic. g. First and second antenne. sip piensis.
Fic. ro. Chitin ribs supporting the margin of the | Fic. 14. Maxilliped.
sucking disk. Fic. 15. Second, third, and fourth swimming legs
Fic. 11. Maxilliped. of male.
PLATE LXII.
Male and female of A. lepidostet and male of A. mississippiensis.
Fic. 16. Dorsal view of male of A. lepidostei. Fic. 19. Maxilliped of female.
Fic. 17. Third leg of male, showing accessory | Fic. 20. Chitin ribs supporting sucking disk of
sexual apparatus. A. stizostethit.
Fic. 18. Chitin ribs supporting margin of sucking | Fic. 21. Dorsal view of male of A. mississippiensis.
disk.
PLATE LXIII.
Male and female of Argulus mississippiensis.
Fic. 22. Dorsal view of female. Fic. 25-27. Second, third, and fourth legs of
Fic. 23. Respiratory areas. male, showing accessory sexual apparatus.
Fic. 24. First and second antenne.
PLATE LXIV.
Male and female of Argulus lepidostet.
Fic. 28. Dorsal view of female. Fic. 31, 32. Second and fourth legs of male, show
Fic. 29. Respiratory areas. ing accessory sexual apparatus.
Fic. 30. First and second antenne.
PLATE LXV.
Newly hatched larva of Argulus lepidostei.
Fic. 33. Dorsal view. Fic. 37. Second maxilla.
Fic. 34. First antenna. Fic. 38. Maxilliped.
Fic. 35. Second antenna. Fic. 39. First swimming leg.
Fic. 36. Mouth tube and first maxilla.

372

COPEPOD PARASITES AND MUSSEL GLOCHIDIA ON FRESH-WATER FISHES. 373

Pirate LXVI.

Females of Ergasilus lanceolatus, elongatus, and megaceros.

Fic. 40. Dorsal view of E. lanceolatus. Fic. 47. Side view of E. elongatus.
Fic. 41. Mouth parts. Fic. 48. Mouth parts.
Fic. 42. Second antenna. Fic. 49. Mouth parts of E. megaceros.

Fic. 43-46. First, second, third, and fourth
swimming legs. |

PLATE LXVII.
Female of Ergasilus nigritus.

Fic. 50. Dorsal view.
Fic. 51. Second antenna.
Fic. 52. Mouth parts.

Fic. 53-56. First, second, third, and fourth swim-
ming legs. |

PLATE LXVIII.
Females of Ergasilus megaceros and E. elongatus.

Fic. 62. Dorsal view of E. elongatus.
Fic. 63-66. First, second, third, and fourth swim-
ming legs.

Fic. 57. Dorsal view of E. megaceros.
Fic. 58-61. First, second, third, and fourth swim-
ming legs.

PLATE LXIX.
Female of Ergasilus elegans.

Fics. 70-73. First, second, third, and fourth swim-
ming legs.
Fic. 74. Nauplius larva of E. ceruleus.

Fic. 67. Dorsal view.
Fic. 68. Second antenna.
Fic. 69. Mouth parts.

PLATE LXX.

Female of Salmincola caltforniensis.

Fic. 75. Dorsal view. | Fic. 79. Ventral view of same.
Fic. 76. Side view. Fic. 80. Mandible.
Fic. 77. Top of head. Fic. 81. First maxilla.
Fic. 78. Second antenna, side view. Fic. 82. Maxilliped.
PLATE LXXI.

Male and first copepodid larva of Achtheres pimelodi.

Fic. 83. Side view of male. Fic. 87. Mouth parts: md, mandible: mx, first
Fic. 84. First and second antenne. maxilla.

Fic. 85. First maxilla. Fic. 88. Second maxilla.

Fic. 86. Dorsal view of larva. Fic. 89. Maxilliped.

PLATE LXXII.

Female of Lerneocera variabtlis.

Fic. 90. Ventral view. Fic. 95. Mouth parts: md, mandible; mx!, first
Fic. 91. Headand anterior thorax, much enlarged. maxilla; mx”, second maxilla; Jb, labium.
Fic. 92. Scale of fish host, showing mode of | Fic. 96. Maxilliped.

attachment. Fic. 97-100. First, second, third, and fourth
Fic. 93. First antenna. swimming legs.

Fic. 94. Second antenna. Fic. ror. Anal lamina.

374 BULLETIN OF THE BUREAU OF FISHERIES.

PLATE LXXIII.

Females of Lerneocera tenuis and L. cruciata.

Fic. 102. Ventral view of L. tenuis. Fics. 105-107. First, second, and third swim-
Fic. 103. First and second antenne. ming legs.
Fic. 104. Mouth parts: mx?, second maxilla; mxp, | Fic. 108. Ventral view of L. cruciata.

maxillipeds. Fic. 109. Dorsal view of same.

PLATE LXXIV.
Females of Lerneocera tortua, cruciata, and pomotidis.

Fic. 110. Mouth parts and antenne of L. cruciata: | Fic. 114. Ventral view of L. pomotidis.
an', first antenna; an, second antenna; mx’, | Fic. 115. Dorsal view of posterior end of body.
first maxilla; mx’, second maxilla; mxp, max- | Fic. 116. First antenna.
illiped. Fic. 117. Second antenna,
Fic. 111. Ventral view of L. tortua. Fic. 118. Maxilliped.
Fic. 112. Dorsal view of horns.
Fic. 113. Antenne and mouth parts, lettering as
in figure 110.

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