he

Sg a,

et ah

Wea

Thaddeus

Ni

s
GR:

a

NOTES ON THE NATURAL HOSTS OF
FRESH-WATER MUSSELS : : By Thaddeus Surber

From BULLETIN OF THE BUREAU OF FISHERIES, Volume XXXII, ro12

DOCUMLENTNENO N77 Sines wisn Vein Selecd aces, Wes neu) Sh SOS ie 1 Issued June 28, 1913

SSE
CS aaeeeEeEeEeEeEeEeEeEeEE—EE—EEE—E=—E>EEE————————————————— eee

WASHINGTON Gt hc 0-0) 20) (GOVERNMENT PRINTING OFFICE: 70 3093: 23 3) 2 9s) 1913

. ‘ a
vf | .
2
“ “ ,
BLEW ey
eo
wen
.?
Sa aabemarpmetemesienaimanin 7pm esata erin ime TIN aaa ners
eae © Li tt pe — aw Cn AE i SA SE ST a id

Fadiet- ths Gre obearroreyenn antes woe, SANTEE eee

een

soe

OTES ON THE NATURAL HOSTS OF FRESH-WATER MUSSELS

&

aia By Thaddeus Surber
_ Assistant, United States Biological Laboratory, Fairport, Iowa

NOTES ON THE NATURAL HOSTS OF FRESH-WATER MUSSELS.
om

By THADDEUS SURBER,
Assistant, United States Biological Laboratory, Fairport, Iowa,

Bd

A study of the conditions pertaining to natural infection of fishes with the larve
of fresh-water mussels was begun by the writer, under the direction of Dr. R. E. Coker,
at the Fairport laboratory in 1910, but was interrupted by assignment to other work,
and, while an effort was made to resume the study in ro11, but little was done owing
to more pressing duty demanding the time. From the last week in June till the close
of November, 1912, however, work was pushed rapidly, 2,815 fish being critically
examined, and considerable knowledge gained in regard to certain mussel species.

The observations given in this paper indicate that the natural hosts of our fresh-
water mussels are divisible into two classes—i. e., specific distributors of particular species,
and accidental or occasional hosts. To the first class belong the skipjack (Pomolobus
chrysochloris), distributor of the niggerhead (Quadrula ebena) ; the sheepshead (A plodinotus
grunniens), distributor of the paper-shell (Lampsilis levissima) and the deer-toe (L. dona-
ciformis); and the shovel-nose sturgeon (Scaphirhynchus platorhynchus), distributor of the
slough sand-shell (L. jallaciosa). The sauger (Stizostedion canadense) may belong here
as distributor of another sand-shell (L. higginst), but it would be unwise to conclude this
on the strength of a single specimen. To the second class, in order of their importance,
belong the crappie (Pomoxis annularis), which has been observed to carry six species;
the sauger, carrying four species; two sunfishes (A pomotts cyanellus and Lepomis pallidus)
each carrying three; the strawberry bass (Pomoxis sparoides), two species; and another
sunfish (Lepomis humilis) and the white bass (Roccus chrysops), one each. A catfish
(Ameirus natalis) carries a few glochidia of the Quadrula type, but I have not been able
to identify the species, owing to accidental loss of material.

Upon consideration, the first class (specific distributors) will be found to agree
closely in geographical range with the species of which it is the host, as might be expected.
This, of course, is not an original theory, but was advanced years ago by Simpson,?
and I am convinced that he was right in his conjecture, and to that end shall attempt to
show that it is the case in at least three species of our mussels.

The second class of infections, accidental or occasional hosts, need not be taken up
systematically at this time. Reference can be made to table 11, however, which shows
the species and number of fishes that were observed to be infected with the various
species of mussels.

@Simpson, Charles T.: The pearly fresh-water mussels of the United States; their habits, enemies, and diseases, with
suggestions for their protection. Bulletin U. S. Fish Commission, vol. xv (1898), p. 282.
103

104 BULLETIN OF THE BUREAU OF FISHERIES.
HOSTS THAT ARE SPECIFIC DISTRIBUTORS.
SKIPJACK (Pomolobus chrysochloris).

This beautiful fish, variously known as ‘‘skipjack,” ‘“‘herring,’’ and, at New Boston,
Ill., as “‘nail-rod,”’ is of rather erratic habits, being abundant at times at certain places
along the Mississippi, and at others one of the rarest of fishes. The fishermen at New
Boston tell me that at times it is very abundant there, usually in September, but at
other times entirely absent. Mr. Will Morris, of Fairport, informs me that a number of
years ago while in a flatboat lying off the point of an island in the Mississippi near
Lansing, Iowa, he caught these fish nearly as fast as he could pull them aboard, using a
common spoon hook. They take live minnows readily also, but the New Boston fisher-
men tell me are very rarely caught in a trammel net, most of those taken being secured
by means of seines, or hook-and-line fishing in the vicinity of thewing dams. Frequenting
the most rapid water in the river, particularly that having a rocky, gravelly bottom,

Skipjack (Pomolobus chrysochloris).

the skipjack is predaceous in habits, feeding mostly on minnows, and Forbes tells us
the young feed on insects. I do not believe this fish is nearly so rare as we might infer
from Dr. Forbes’s records as given in his ‘‘Fishes of Illinois,’ but that the fishermen pay
no attention to it at all, considering it a nuisance and immediately throwing overboard
all that are caught.

The geographical range of this fish, as given by Jordan and Evermann, is ‘“‘ Mississippi
Valley, etc., abundant and resident in larger streams; introduced into Great Lakes.
Also in Gulf of Mexico.”

The range of Q. ebena as given by Simpson is “Mississippi drainage generally
except its western portion; Alabama and Tombigbee Rivers; northeast Texas(?).”’

The importance of the skipjack to mussel culturists prompts the hope that it may
be possible in the course of time to propagate this fish artificially, and in the meantime
it is suggested to those who believe in the introduction of western forms into eastern
waters to try one of its eastern congeners, P. pseudoharengus or P. e@stivalis as an experi-
mental host for this desirable mussel. The introduction of mussels into other waters by

NATURAL HOSTS OF FRESH-WATER MUSSELS. 105

transportation of the infected fish, entirely feasible with some fish,* would not be
possible in this case, as the skipjack is very delicate and will not admit of handling
during the warm summer months.

SHEEPSHEAD (A plodinotus grunniens).

From its feeding habits we should expect to find this fish more often infected than
any other species. In writing of it Dr. Forbes ® says:

‘This fish is of a sluggish habit, living on the bottom of muddy waters, where it feeds especially on
mollusks, the shells first being crushed by the powerful, paved millstone-like, pharyngeal jaws. Often
the stomach contains only the soft bodies and opercula of gastropod mollusks, the crushed shells having
been thrown out. Crawfishes are also sometimes found in the food. Half-grown specimens feed largely
on aquatic insects, especially the larve of May-flies, mingling larger and larger proportions of mollusks
with this food as they increase in size, until they come finally to depend almost wholly upon water
snails and the relatively thin-shelled clams.

As it is known to be the specific host for both L. levissima and P. donaciformis, it
is of rather more than usual interest.© It can no doubt readily crush the papery shells of
levissima, and, from their small size, swallow entire the shells of donactformis, from which
we can readily understand the enormous numbers that are attached to the gills of
this fish.

The geographical range of the fish is given as ‘‘Great Lakes to Texas and Georgia;
abundant in all lakes and large streams west of the Alleghanies and east of the plains”’
(Jordan and Evermann).

Simpson gives the ranges of the two mussels as follows:

L. levissima: ‘‘ Mississippi drainage generally; eastern Texas, southern Michigan,
western New York.”’

@ Dr. Ortmann, in an interesting article in a recent issue of ‘‘ The Nautilus’’ (vol. xxv1, p. 51), records the accidental intro-
duction of the ‘‘ pocketbook’’ (L. ventricosa) into the upper Potomac drainage in Maryland and West Virginia.

b Forbes, S. A.: Fishes of Illinois, Natural History Survey of Illinois, State Laboratory of Natural History, vol. m, p. 324.

c Since the above was written the author has had the opportunity to examine a number of fish taken by him in White and
Cache rivers near Clarendon, Arkansas. During the first half of January (1913) 18 specimens of A plodinotus grunniens were
secured, eight of which bore natural infections, and from the number of glochidia borne by each fish I should accept it as the
specific host of Lampsilis (Proptera) purpurata; five examples were infected on the gills and another both on gills and
caudal fin. The cysts are very large and consequently vety noticeable. While all are not of the same development the growth
in the majority of cases is very marked; the infant mussels have assumed about the development indicated in the figure of levis-
sima shown in figure 2, plate xxix. Itis presumed these fish became infected some time during the autumn, but as many gravid
mussels of this species, all with active glochidia, were taken during January, some may have become infected more recently. In
these infections the number of infant mussels borne by individual fish varied from 68 to as many as 500 in two cases. The glo-
chidium of purpurata resembles very closely that of L. (Proptera) alata both in shape and size, measuring 0.200 by 0.360 mm.; the
hooks, however, are better developed than in alata.

A still more interesting discovery is the finding of a number of glochidia of Quadrula heros, heavily encysted and of consider-
able development, on the fins of two of these A plodinotus. ‘This glochidium being of the hookless type it was naturally supposed
-to be a gill parasite, but this does not seem to be the case, as none were found on the gills of the fish.

In the White River material is also a specimen of rock bass (A mbloplites rupestris) carrying on its gills six glochidia of Arcidens
confragosa beautifully encysted and of considerable development. The hooked glochidium of Arcidens is closely related, in form
at least, to the Anodonta group, one species of which (cataracta), according to Lefevre and Curtis (Bulletin U. S. Bureau of Fish-
eries, vol. XxX, p. 158), would not metamorphose on the gills of the carp. A crappie (P. annularis) was also secured bearing the
same species on the gills; but this mussel is probably more frequently found on the fins of fishes, as two hickory shad (Dorosoma
cepedianum) were taken bearing considerable numbers on the fin margins, particularly the caudal, where they are deeply embedded
in the epithelium.

106 BULLETIN OF THE BUREAU OF FISHERIES.

P. donactformis: ‘‘Mississippi drainage generally; Alabama River area; southwest
to the Trinity River, Tex.; Michigan.”

In artificial infections this fish takes readily almost any glochidia of the Lampsilis
group, but with indifferent results, more probably due to the difficulty of handling it in
hot weather than from any other cause.

SHOVEL-NOSE STURGEON (Scaphirhynchus platorhynchus).

Sturgeons as a rule are bottom feeders, and this species is no exception, so that we
should expect to find it very frequently infected. Such, however, does not seem to be
the case. The heavy gill filaments of this fish render difficult the detection of glochidia;
therefore all that were obtainable were carefully gone over, and it is not believed any
were overlooked which were carrying larve in any numbers. On October 15 and again
on November 7 specimens were taken holding larve of Lampsilis jallaciosa, and these
were in sufficient numbers to indicate that it is the specific host of this particular species.

While it is unsafe probably to consider this fish the only distributor of jallaciosa,
it is interesting to note the known geographical ranges of the two species, which is as
follows:

S. platorhynchus: “Mississippi Valley and streams of the Western and Southern
States” (Jordan & Evermann).

L. fallaciosa: ‘‘Upper Mississippi drainage; south to the Cumberland River, Tennes-
see, and to Arkansas; Red River of the North?”’ (Simpson).

MUSSELS AS PARASITES.

We shall now consider the matter from another point of view, taking up in their
order the various mussel species as parasites. It will be noted that all species considered
in this study are gill parasites with one exception, A. corpulenta, and consequently nearly
all of commercial value.

SLOP-BUCKET (Anodonta corpulenta).

But one fish has been taken bearing larve on the external parts, and this is found
to be corpulenta. On November 10, 1910, along the river shore within the grounds of
the biological station, a young skipjack about 3 inches in length was picked up which
held 24 glochidia, mostly on the caudal fin, but a few on ventrals and pectorals. By
reference to the accompanying figure (fig. 1, pl. xxrx) it will be noted that encystment
is incomplete, though but a small portion of the dorsal edge of the shell protrudes, and
that the infection is quite recent is further shown by the condition of development in the
adductor muscle. This glochidium is saddled over the edge of the caudal fin and grasps
two of the cartilaginous rays up almost to the adductor muscle; the other glochidia
occupied relatively the same positions on the fins as shown in this figure.

NATURAL HOSTS OF FRESH-WATER MUSSELS. 107

YELLOW SAND-SHELL (Lampsilis anodontoides).

During the latter part of June and early in July this mussel was found on the two
species of crappie and on A pomotis cyanellus and Lepomis humilis, but in such limited
numbers that it is extremely doubtful if any of these fish are the actual host, as the
greatest number occurring on any one species was six. As this time is the height of
the spawning season of this particular mussel, and all the infections were recent, it is
presumed they were more or less accidental.

Some sunfish infected artificially with glochidia of this mussel July 1, 1911, appar-
ently took well and were deeply encysted at the end of three and three-fourths hours,
but two days later not a single glochidium could be found on any of the fish, due proba-
bly to unfavorable conditions. On June 27, 1910, a lot of fish, chiefly Pomoxis and
Lepomis, with a few Micropterus, A plodinotus, and Roccus were infected and apparently
took well, but the glochidia never completed their metamorphosis. However, on August
II, 1910, a few metamorphosed on a sunfish (A. cyanellus) in four days, about 1 per cent
of those encysted.

SLOUGH SAND-SHELL (Lampsilis jallaciosa).

On June 27 a crappie (P. annularis) was taken holding 16 glochidia of this species,
but it was not again found till October 15, when a sturgeon (S. platorhynchus) was
taken holding 125. On November 7 another sturgeon was taken holding 56.

This glochidium does not, as a rule, take very near the tips of the filaments in the
sturgeon, but rather deep, a great many as deep as the fork of the filament, and encyst-
ment is very heavy. The October infection indicates but very slight development,
or none at all; cysts enormous. Examination of the November infection reveals the
fact that the adductor muscle is dividing and traces of the foot are clearly discernible.
It is believed these sturgeon become infected sometime during September or October,
and the metamorphosis would, therefore, not be completed till some time during the
following spring.

HIGGINS SAND-SHELL (Lampsilis higginst).

The only fish so far taken which unquestionably holds this glochidium is a specimen
of Stizostedion canadense taken October 4, 1912; it holds approximately 600 glochidia.
The infection was recent and no development is clearly indicated; cysts very heavy.

PAPER-SHELL (Lampsilis levissima).

For the past three years we have been taking sheepshead (A plodinotus grunniens)
bearing enormous numbers of young /evissima, generally in a high state of development.
The sheepshead, from its habits, should be expected to be found more frequently infected
than most any other species of fish, yet the percentage of infected fish is small.

Only 2 per cent of the fish taken during the period from June to November were
infected with this larva, the number carried by each fish varying from 112 to 850. It
was hoped that a critical study of the material would indicate the period of parasitism,
but such is not the case, though I am of opinion that it covers a period of nearly a year.

89967°—13 2

108 BULLETIN OF THE BUREAU OF FISHERIES.

The only fish so far taken carrying what is apparently recent infection is one taken October
21, but only a few, about 1 per cent, are of this stage, i. e., the glochidium still simple.
The next stage is indicated in specimens secured October 15, where the growth is quite
decided, the infant mussel having assumed a nearly circular form when viewed from the
side; this phase is clearly shown in figures 2 (side view) and 3 (postero or antero ventral
view). In figure 2 the larval mussel is on the extreme tip of the gill filament, while
figure 3 is encysted about 3 mm. back from the tip and on the flat side of the fila-
ment. Another fish, taken October 30, holds larval mussels in a more uniform state of
development, of a stage clearly shown by figure 4; by reference to this figure it will be
found that the young mussel has apparently grown more rapidly in length than in
height, and that in the region of the umbones, both anteriorly and posteriorly, it has not
grown at all, except in thickness, giving it a curious depressed effect there. Figure 4
exhibits the sharpness of the ventral points of the glochidial shell on the upper side,
caused by the growth of the shell of the young mussel expanding the glochidial shell;
in figure 5 a dorsal view is given of another specimen of the same relative development
to show increase in thickness.

The greatest development seems to be reached during October, when they have
assumed the shape and size indicated in figures 6 and 7, where it has increased three to
four times in length over glochidium and the inflation (thickness) is so marked as to
suggest anything but the parent shell, when viewed dorsally (fig. 7). [his stage has
been shown before (Coker and Surber, Biological Bulletin, vol. 20, p. 179-182, fig. 5,
6, and 7). It is believed that at this stage the parasitism is completed, or nearly so,
and this belief is strengthened by the fact that on November 2 a fish was taken holding
comparatively few (120) mussels and a number of ruptured cysts which had probably
held others a very short time previously, though it is of course possible that the ruptures
may have been caused by other parasites, but this is not deemed probable. We might
infer from this that the fish became infected either the preceding spring (1912) or during
September of the preceding year (1911), the latter seeming the more probable. Levis-
sima with ripe glochidia has been taken in the vicinity of Fairport during April, June,
and September.

So far, this mussel has been found on but one other species of fish, the crappie, in
which the same development is indicated as occurs in the sheepshead.

TasBLe I.—NumBER OF LaRvaL L. LavISSIMA CARRIED BY THE Host.

Date Number 2
Species of fish. eectired of glo- Locality.
2 chidia.

Aplodinotis eriimniens see secretes seer raiteraicek-ti- late esteleleter si holeeisismimn cis teiet-tale eletels sit) June 16,1910 670 | Fairport, Iowa.
Oct. 18,1910 375 Do.
Oct. 15,1912 325 Do.
Oct. 17,1912 112 Do.
Oct. 15,1912 850 Do.
Oct. 30, 1912 200 Do.
Oct. 21,1912 240 Do.
Nov. 2,1912 120 Do.
Nov. 9,1912 549 Do.

IRN Ge SAM IET Es sogocantddoadtsando gas neon 0DbboosanagoODasboUdaKddGobHqNbaaDeRGOO Nov. 17,1912 12 Do.
Noy. 21,1912 210 Do.

NATURAL HOSTS OF FRESH-WATER MUSSELS. ioe)
Mucket (Lampsilis ligamentina).

On the 26th of September a rather large Roccus chrysops was taken holding upward
of 200 glochidia of this species; cysts are heavy but glochidia show no development at all,
so that it is presumed to be a recent infection.

A great many other fish were taken during September and October, principally
crappie and sunfish, infected with this mussel, but as the crew of the station were at
work infecting and liberating fish with this larva, all were presumed to be artificial
infections. No Roccus had been artificially infected previous to September 26, so that
the above record is deemed permissible.

BLACK SAND-SHELL (Lampsuilis recta).

The only time this mussel has been found a natural parasite was July 2, 1912, when
a Lepomis pallidus was taken bearing 35 glochidia. The infection was recent, deeply
encysted, and I have no doubt would have metamorphosed in a very short time, the
fish being extremely strong and robust.

DEER-TOE (Plagiola donaciformis).

This small mussel, so far, seems to be found almost exclusively on the sheepshead,
the only exception being a sauger taken quite recently. Discovered first at New Boston,
Til., in August, 1910, it has since been found at frequent intervals, both there and at
Fairport.

The number of young mussels found on a fish varies considerably, but is usually
great, a fish taken October 30 holding about 2,800, which is the greatest number found.
The duration of parasitism is problematical; no fish have been found recently infected,
all infections so far found being highly developed. As we have secured gravid mussels
of this species with fully developed glochidia only during the latter part of July, it
seems probable, and is possible, that the enormous development indicated occurs in the
short space of two months, but this of course can only be proved by artificial infection
of the specific host. Specimens of least development, so far known, are some taken
July 20, 1911, one of which is shown in figure 8 (postero-dorsal view) ; this would indicate
one of two facts, either that it was an infection of the previous year, in which case
growth is comparatively slow, or that it was very recent and growth correspondingly
rapid. On a fish taken August 16 occur 1,495 young mussels, the development of
which is very great, far exceeding that shown previously in J/evissima; one in side
view is shown by figure 9, which is found to have increased seven times in length,
and about three and one-half times in depth over glochidial shell, yet all on this fish
were not uniformly developed, as is shown in figure 10 (a). Figure 10 shows a portion
of a filament with young mussels in situ, two of which are on the edge, while the other
(a) is encysted on the flat side of the filament.

110 BULLETIN OF THE BUREAU OF FISHERIES.

TABLE II.—NUMBER OF LARVAL P. DONACIFORMIS CARRIED BY THE Host.

‘ Date Number i
Species of fish. Bectred of glo- Locality.
. chidia.
A PlodiNOUUS ELUNE tele oe) =leletes slolelo wiclalaleiclelslete(eiels cleinieialaie cielseisialsencicinisnisisc asians Aug. 9,1910 1,100 | New Boston, Il.
Aug. 15,1912 300 Do.
Aug. 16,1912 1,495 Do.
Dowod doteeene 1, 200 Do.
Aug. 15,1912 76 Do.
Aug. 22,1912 2 | Fairport, Iowa.
Aug. 24,1912 280 Do.
Oct. 30,1912 2,800 Do.
Nov. 9,1912 1,000 Do.
Stizostedion\canadenser yee cy. /sjcis sicielsteveisievsis cis] -seielovetaleie s)ete leyareileters ote eisisieleierasteteyereinielersisjeia| sevens Gowren ine 1, 800 Do.

BUTTERFLY (Plagiola securis).

But a single glochidium, well encysted, has been found by the writer, this being
found ona sunfish (A pomotis cyanellus) taken July 1, 1912; no development was indicated.

Experiments in artificial infection of the black bass, crappie, sunfish, and catfish
with this larva have proved unfavorable, so that we must conclude the specific host is
as yet unknown.

BULLHEAD, SHEEPNOSE (Pleurobema @sopa).

A sauger (S. canadense) was taken July 20, 1911, holding 17 glochidia of this mussel.
As the anterior and posterior adductor muscles were clearly defined and the foot more or
less conspicuous, indications are that this fish is at least an occasional host of this larva.
As the mussel itself is not at all common, the sauger may eventually prove to be the
specific host. An infection is shown in figure 17.

NIGGERHEAD (Quadrula ebena).

The discovery of the specific host of this mussel on August 13, 1912, was a great
gratification, occurring as it did after almost three years’ experimentation. Repeated
failures in obtaining artificial infections with all the species of fish obtainable in the
vicinity of Fairport led me to search for fish not previously taken, of which the skipjack
(P. chrysochloris) was about the only one remaining. The taking of a specimen of this fish,
June 18, 1910, by H. Walton Clark, was overlooked till after the August, 1912,
material was identified, when his note was looked up and later the fish itself secured and
found to be heavily infected. Mr. Clark, while recognizing at the time of taking that his
I9IO specimen was carrying glochidia in great numbers, was unable to identify the
species of mussel owing to lack of material, no glochidia of QO. ebena being available at
that time for comparison. Owing to the great commercial value of this shell, which is
exceeded by none, the final discovery of the host is of far-reaching importance.

During the season of 1912, 15 specimens of Pomolobus were secured in the vicinity
of Fairport and New Boston, the 5 specimens secured during August all bearing glochidia
in large numbers, ranging from 1,895 to 3,740 for each fish. During this month little
development of the glochidia was shown which would indicate recent infection, but a

» NATURAL, HOSTS OF FRESH-WATER MUSSELS. III

specimen taken at Fairport, September 11, had only 48 glochidia remaining, and two
specimens out of a total of nine taken at New Boston, September 24, held 26 and 3r1,
‘respectively, all the September materia! indicating much development. The same
results are shown by some material from the upper Mississippi which Mr. W. B. Gorham
secured while with the reclamation work of the steamer Curlew, when, on August 26, at
La Crosse, Wis., he secured one fish holding 365 glochidia, well along in development, and
another fish at Genoa, Wis., September 23, with development about completed. In the
vicinity of Fairport ebena has been secured with well-developed embryos during the last
week in May and during June, July, and August. This would indicate a comparatively
rapid metamorphosis, which, in my opinion at least, does not much, if at all, exceed two
months.

A study of the material shows us that ebena undergoes no important increase in
size of shell, and consequently no change in form, during metamorphosis. Figure 11
shows a glochidium (side view) on the edge of a filament. By reference to the figure it
will be noted that considerable development is indicated, the posterior adductor showing
in place, and the foot considerably developed; this was taken August 13, and figure 12
shows dorsal and ventral views of the same development. In the specimens taken
September 24, shown by figure 13, the development is very clearly defined, the foot
having reached what might be considered normal size, while the position of the anterior
and posterior adductors and the protractor pedis is distinct; it is believed this young
mussel would have left its host in a very short time. In the specimens taken June 18,
1910, practically no development at all has occurred; the distal third of a gill filament of
this infection is shown in figure 14.

Particular attention is called to figures 12 and 13, where the cysts are shown off
to one side of the young mussel, a characteristic feature of those which have attained
sufficient development. It seems the young mussel has shifted its position, migrating
as it were from its normal position in the cyst to a new one among the delicate filaments,
disarranging them as indicated in the figure (12) on the right side; this movement is
preliminary to its ultimate freedom. The young mussels are now lying on the surface
of the filament beneath the mucous membrane covering it, while the epithelial cells
forming the cyst proper remain unbroken, so that it has evidently pushed along beneath
the membranaceous covering to its present position, the membrane having now adapted
itself to the new conditions and formed, as it were, a new cyst which covers the entire
filament and gives to the parasite much increased freedom of movement. This condition
is more clearly shown by reference to figure 18, where the distinctly swollen area com-
prising the new cyst is accentuated, though the magnification in this figure is much less
than indicated in figures 12 or 13.

In the more recent infections—that is, the young still in the glochidial stage, as shown
by figure 14—this remarkable condition does not exist, the development being such that
the animal has no power of locomotion as yet. On the other hand, in specimens taken
during September, there are many cysts having the appearance of these shown in figure
13, simple, hollow, globular areas suggesting small tumors, unmistakably the former
abode of some young mussel which has completed its metamorphosis and departed with-

112 BULLETIN OF THE BUREAU OF FISHERIES.

out apparent serious injury to the cyst. This condition is interesting, nothing like it
having previously been noted in the parasitism of any of our mussels, so far as I know,
and the causes leading up to it will bear careful investigation. This can be done only by
a thorough study of the relations existing between host and parasite, in which connection
it will be well to study in detail the structure of the gills of the host.

TaBLE IT].—NuMBER OF LARVAL Q. EBENA CARRIED BY THE Host.

Date Number

Species of fish. of glo- Locality.
secured. | chidia.
i}
‘Pomolopusichrysochlormsyeeciicseisciee ceeiaceeceeaniceciereceieiereeeeiere Aug. 13,1912 2,100 | Pearl Slough, Fairport.
RG dowieeces 3,740 Do.
Aug. 14,1912 1,895 | Buttermilk Slough, Fairport.
Been doveerteer 2,700 | Upper end Geneva Island.
Aug. 17, 1912 3,200 | New Boston, IIl.
Aug. 26, 1912 365 | La Crosse, Wis.
Sept. 11, 1912 48 | Fairport, Iowa.
Sept. 24, 1912 26 | New Boston, Ill.
baad GMEse6onne 31 Do.
Sept. 23, 1912 9 | Genoa, Wis.
June 18, 1910 2,570 | Fairport, Iowa.

MONKEY-FACE (Quadrula metanevra).

During the early part of July five blue sunfish (Lepomis pallidus) and one green
sunfish (A. cyanellus) were taken bearing a comparatively small number of glochidia of
this mussel. The two heaviest infections are one of 50, the other of 69, and it is there-
fore probable the sunfishes may be found to be the specific hosts of this mussel. By
reference to figure 15 it will be found that one of the infections, taken July 2, is develop-
ing, the adductors having become clearly defined and rudiments of the foot apparent.
No change in form nor increase in size of shell is anticipated in this species.

TaBLE IV.—NUMBER OF LARVAL Q. METANEVRA CARRIED BY THE Host.

Species of fish Date ak ates len epee
pecies of fish. of glo- cality.
secured. | chidia.
Wepomis! pallid usty- erttttraael ela era sceetettere ce eile tine ate tetheieie le cles -faichee ets July 1, 1912 6 | Fairport, Iowa.
July 2, 1912 50 Do.
ek doe... 4 I Do.
gonue COsca0¢an0 6 Do.
Rene Gksdocane 69 Do.
A POMOUISICVANELLUS Hel yepaerceistetarebrerleie tae tetriiteer tenis tetctactetrelsinieritbisvestcetelval tetetere GM@saa5a600 15 Do.

BLUE-POINT; THREE-RIDGE (Quadrula plicata).

The only fish so far taken infected with this species was on June 28, 1912, when a
sauger (S. canadense) carrying 28 and a crappie (P. annularis) 4 glochidia were secured.
The development is decidedly progressing as indicated in figure 16, where the foot and
both adductor muscles are clearly defined. The figure (16) is a glochidium attached to
edge of gill filament of the sauger.

NATURAL HOSTS OF FRESH-WATER MUSSELS. 113
PIMPLE-BACK (Quadrula pustulata).

But two glochidia of this species have so far been detected and this on a crappie
(P. annularis) taken September 12,1912. While it is rather late in the season to expect
to find this mussel still parasitic, it is not believed that the identification is wrong, yet
the development should have progressed more rapidly than is the case in this instance.

PIMPLE-BACK (Quadrula pustulosa).

October seems extremely late to find any Quadrulas persisting, but the gills of a
crappie taken the 17th of that month reveals a single glochidium of what I am com-
pelled to regard as this species. No development whatever is indicated and the pres-
ence of the glochidium at this late season may be due to some freak physiological
characteristic not easily understood.

QUADRULA SOLIDA.

Two sunfish (Lepomis pallidus) were taken July 1, 1912, bearing glochidia of this
mussel, one having 50 present, the other only 6. The development is similar to that
noted in plicata, the foot and adductors being clearly indicated. The shell itself is not
at all common in this region, and one would naturally expect to find few fish infected.
The glochidium of this species closely resembles that of ebena and might be mistaken
for the latter by a careless observer, but may be recognized by its greater comparative
depth and shorter, straighter hinge line.

PIG-TOE (Quadrula trigona).

From the frequency with which this shell is found in the vicinity of Fairport, it is
surprising more infected fish are not taken, its spawning season being July and August.
So far only a single black crappie (Pomoxis sparoides) taken June 25, 1912, has been
found infected, and it held but three glochidia, none of which showed any development
whatever, thus indicating recent infection.

SUMMARY.

In conclusion attention is directed to the table of fish examined (table v), following.
The remarkably small percentage of fish infected in a state of nature will be apparent
at once, even of those species known to carry glochidia, if we except the skipjack
(Pomolobus chrysochloris). In the case of the sheepshead, known to be the specific host
for two species of mussels, the percentage is about 324, while in Pomoxis annularis, which
carries more species of mussels than any other fish, it is only seven-tenths of 1 per cent.
Out of a total of 38 species examined, numbering some 2,815 individuals, only 46 fish were
infected, but of course only 11 species are apparently susceptible to natural infection.
Further investigations will reveal much, the work having only begun. A summary of
the present known hosts is shown in table v1.

Il4 BULLETIN OF THE BUREAU OF FISHERIES.

By reference to table v the advantages of artificial infection can be readily
imagined when the small percentage found infected in a state of nature is considered.
Some one has long ago estimated that in the case of some fishes but 10 per cent of the
eggs deposited naturally are even fertilized, whereas by artificial means it is now an
established fact that fully 90 per cent, and even better, is not only possible, but a rule,
in handling these same fishes. Now in the mussel the eggs are fertilized and the young
developed ready for their parasitic life while still in the gills of the parent, so that all
man has to do is find the specific host of a given species, procure that host, and load it
to the limit, which may exceed the optimum infection of Lefevre and Curtis % in some
cases. The simplicity of the proceeding is startling when we consider the ease with
which the glochidia can be procured, a fair sized mucket (L. /igamentina), for instance,
producing as many as 3,500,000 young and the niggerhead (Q. ebena) about 350,000.

TABLE V.—FisH CAUGHT AND EXAMINED FOR NATURAL INFECTION, JUNE TO NOVEMBER, 1912.

June-July. August. September. October. November. Total.
Species of fish.
Exam-| In- |Exam-| In- |Exam-| In- |Exam-| In- |Exam-| In- |Exam-| In-
ined. |fected.| ined. |fected.) ined. | fected.) ined. | fetced.| ined. | fected.) ined. | fected.
x. Petromyzon castaneus I
2. Petromyzon concolor............. id aaa 4|-
3. Polyodon spathula............... 1p 2
4. Scaphirhynchus platorhynchus...|....... 65
5. Lepisostets osseus...............- 7
Oh EEE CAKES oe aonepooodepdooconeay 2 : 8 |.
7. Ictalurus furcatus................ uawanda ia : 3 |!
8. Ictalurus punctatus | eps ae 168
9. Ameiurus natalis................. 8
to. Ameiurusnebulosus.............. I
rr. Ameiurus melas 61.
12. Leptops olivaris 67
13. Carpiodes carpio f
TA Carpiodesiveliter- m-th decnoe 4
15. Cycleptus elongatus.............. 2
x16. Minytrema melanops............. i
17. Moxostoma breviceps............- i
18. Moxostoma aureolum............. a
19. Hiodon alosoides. ................ I
20. Pomolobus chrysochloris. ........ 15
21. Dorosoma cepedianum........... 16
22. Hsox vermiculatus............... 2
23. Anguilla chrisypa . 3
24. Pomoxis sparoides. . 258
25. Pomoxis annularis................ I, 155
26. Ambloplites rupestris............. 2
27. Apomotis cyanellus............... 58
28. Apomotis symmetricus........... I
29. Lepomis humilis................- 43
30) Wepomiis|pallidts. 0)... +--.---»- 245
31. Eupomotis gibbosus.............- 4
32. Micropterus dolomieu............ 4
33. Micropterus salmoides...........- 22
34. Stizostedion vitreum,............ 9
35. Stizostedion canadense............ 95
36. Roccus chrysops..............--.- 2
37. Morone interrupta...............- 73
38. Aplodinotus grunniens........... 322
Potale ea ethno ieneek ee Ee 2,815 46

@T,efevre, George, and Curtis, Winterton C.: Studies on the reproduction and artificial propagation of fresh-water mussels.
Bulletin of the Bureau of Fisheries, vol. xxx, D. 159. :

NATURAL HOSTS OF FRESH-WATER MUSSELS. II5

TaBLE VI.—NatTuRAL Hosts oF FRESH-WATER MUSSELS.

Species of fish.

Scaphirhynchus plato-
THYNCHUS Ys. cease. cls

Ameiurus natalis.......

Pomolobus chrysochlo-

Pomoxis sparoides.....
Pomoxis annularis... .
Apomotis cyanellus...
Lepomis pallidus

Lepomis humilis....... |

Stizostedion canadense.

Roccus chrysops....... :

Aplodinotus grunniens.

Species of mussel and number of fish infected.

4 a a B 3 na 3 | «& 3 Cj a a Cy ao 3 a
(lon ete] ot & By pas} ou a § — mle re ee) 7

Sa | el ice g@)/=a|/= |] Su] oy] oe 3 se} s | 28] 38] Ee
Sy 2g |fq 26/25) a8) a) Sse Sai se | sei ssississi se
Bo l|eS| BS | we | da] Se) Ss) we] Oo) re / 9s) VS | Ce) Oe | ea] es
Ge} Go|) ch) ce) ce BE] 22S) ae/ 58) eS] e¢8| s3] 08] a9] a9] ot
Bs|& g Be} eal as | Fo) 7] 2 x ag] 3 ey || S|] El hehe
=i H Hw n a cl a a ey a a Qa Qa a Qa a

Norte.—Anodonta cor pulenta has been found but once, a young Pomolobus chrysochloris carrying a few on the fins; being an
external parasite, it is not included in this table. A meiurus natalis is included in the table because it was found to harbor one
glochidium, the species of which was, however, indeterminable.

EXPLANATION OF PLATES.
PLATE XXIX.

Fic. 1. Glochidium of slop bucket, Anodonta corpulenta, on caudal fin of a young skipjack, Pomo-
lobus chrysochloris.

Fic. 2. Young paper shell, Lampsilis levissima, on gill of sheepshead, A plodinotus grunniens (side
view) in an early stage of development.

Fic. 3. Postero- or antero-ventral view of young levissima of about the same development as
figure 2.

Fic. 4-5. Another stage of development of levissima, figure 4 representing side and figure 5 dor-
sal views.

Fic. 6-7. Side and dorsal aspects of lJe@vissima upon reaching what is considered its greatest
development as a parasite.

PLATE XXX.

Fic. 8. Postero-dorsal view of young deer-toe, Plagiola donaciformis, on gill of sheepshead, Aplo-
dinotus grunniens.

Fic. 9. Side view of donaciformis on gills, the metamorphosis about completed.

Fic. ro. Portion of gill of Aplodinotus with young donaciformis in situ.

Fic. rr. Glochidium of niggerhead, Q. ebena, on gill filament of skipjack, Pomolobus chryoschloris,
taken August 13. :

Fic. 12. Dorsal and ventral views of ebena of same relative age as figure 11.

PLATE XXXII.

Fic. 13. Quadrula ebena presumed to have about completed its metamorphosis; a specimen taken
September 23, 1912.

Fic. 14. Distal third of gill filament with glochidia of ebena in position.

Fic. 15. Glochidium of Quadrula metanevra on gill filament of sunfish, Lepomis pallidus.

Fic. 16. Glochidium of Quadrula plicata on gill filament of sauger, Stizostedion canadense.

Fic. 17. Glochidium of Pleurobema @sopa on gill filament of the sauger (S. canadense).

Fic. 18. Young ebena on gill filament, showing shifted position.

116
O

PLATE XXIX.

ot

IPG MOOG:

Bow, Wh Sy 1s oy LEU,

OAnmm,

FIG. 9.

0.2mm.

JES, Ie

. Io.

FIc

»
»)
5
>
ate
»
)
}
a)

ed

GHo LS

EU, WA.

PLATE XOX XT.

BULL US. Ba Ee hom.

Fic. 18.

Fic. 14.

- (3!
Gs
4
aL
Wy

ng

ig
at
is
Ye

seer
i aS

1H
Oo -
4 Uv
a 2
ano

ow
rh
ica
dp)

Qn
o co
© s

on =
Ba &
Go) N
= =
(e) =
= a.
al E
Ay =