EXCHANGE

SCIENCE

THE FISHES OF LAKE VALENCIA,
VENEZUELA

BY

A. S. PEARSE

PROFESSOR OF ZOOLOGY

MADISON

SI

UNIVERSITY OF WISCONSIN STUDIES

IN SCIENCE
NUMBER 1

THE FISHES OF LAKE VALENCIA,
VENEZUELA

BY

A. S. PEARSE

PROFESSOR OF ZOOLOGY

MADISON
1920

CONTENTS

Introduction , 5

Lake Valencia , . '.", 7

List of Fishes with Remarks on Geographical and Eco-
logical Relationships 11

Food of Fishes 18

General Remarks on Food 26

Parasites of Valencian Fishes 28

List of Fishes with Remarks on Parasites 42

General Remarks on Parasites 47

Conclusions 50

Bibliography . . , 51

73074R

THE FISHES OF LAKE VALENCIA, VENEZUELA

> j -> j ' j j j ju j j '
INTRODUCTION 5"! '

Though the fishes of tropical lakes have often been studied
by systematists, morphologists, and those interested in geo-
graphic distribution, they have received scant attention from
ecologists. There are indeed few situations where ecological
investigations can be made in tropical fresh-water lakes. Most
of the lakes in Central Africa are brackish or salty. In South
America, the large lakes in the Amazon basin all fuse with the
rivers during the rainy season; those on the west coast are at
great altitudes and have a very scanty fish fauna. Lake
Valencia was selected from among those in northern South
America and Central America because it seemed to present
typically lacustrine conditions and to promise a reasonably
varied and abundant fish fauna.

The writer carried on investigations in Lake Valencia and
the rivers draining into it from July 4 to July 31, 1918; then
studied the rivers between the lake and the coast to August 5,
fishing in the Rio Tuy and its tributaries at El Concejo and
Caracas.

The University of Wisconsin granted a special fund for
travelling expenses; Dean C. H. Eigenmann induced the
University of Indiana to furnish a complete outfit of nets and
fishing tackle; and the Zoological Laboratory at the University
of Wisconsin generously provided the remainder of the outfit,
except a deep sea thermometer and apparatus for gas analysis
which were loaned by Mr. C. Juday of the Wisconsin Geological
and Natural History Survey.

In Venezuela the government officials and many private
citizens showed the greatest interest and courtesy. The writer
is particularly indebted to two Americans, Dr. H. Pittier and
Mr. Carl Magnus; an Englishman, Mr. Charles Lazzari; and

6 UNIVERSITY OF WISCONSIN STUDIES

to many Venezuelans, chief among whom are Coronel All
Gomez, Don Carlos Delfino, Dr. Juan Iturbe, and a most
admirable guide and compadre, Agapito Blanchar. It is a
pleasure also to acknowledge the great help received from the
writings and general advice of Dr. C. H. Eigenmann, whose
Stores ofc wisdopj relating to South America and its fishes were
•ff e'ely placetf'at 'tfty, disposal. Dr. Eigenmann also identified
<dj :i}i£ ;?jsKes- collected. The following persons were kind
"erio'ugh to worK up'otner groups of animals: Dr. J. B. Malloch,
insects; Dr. H. J. Van Cleave, acanthocephalans; Dr. N. A.
Cobb, nematodes; Mr. Bryant Walker, molluscs; Dr. Ruth
Marshall, mites; Miss M. J. Rathbun, decapod crustaceans.

The equipment used for fishing was as follows: 1 9-inch
dip net with 6 ft. handle; 1 seine 50X4 ft., Y± in. mesh,* with
4X4 bag in middle; 1 seine, 30X4 ft., % in. mesh; 2 common
sense minnow seines, 4X10 ft. and 4X25 ft.; 2 gill nets, 4X75
ft., % in. mesh; 2 gill nets, 4X75 ft., 1 in. mesh; 2 gill nets,
4X75 ft., V/z in. mesh; 2 gill nets, 4X75 ft., 2 in. mesh; 2 gill
nets, 4X75 ft., 3 in. mesh. Besides these nets a square dip
net 4X4 ft., a cast net, a trammel net, and equipment for trot
lines were taken along, but never used. There were no fishes
large enough for the trammel net. The cast net purchased in
the United States was found to be much inferior to those in use
by the Venezuelans; the latter were of great value, especially
in the swift streams.

*A11 references to meshes of nets indicate "bar mesh.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 7

LAKE VALENCIA

Lake Valencia lies between two mountain ranges about
thirty miles south of Porto Cabello, Venezuela. It is surrounded
by a basin of considerable size and the level of the lake has
apparently been falling for some time. The shores, except
around the islands, are everywhere composed of soft mud
which supports a thick growth of rushes (Fig. 1). A mile or
more from the shores the soil consists of soft black bottom
deposits containing numerous weathering snail shells and the

FIG. 1. Rush-grown shore of Lake Valencia near Maracay.

remains of other aquatic organisms. According to Dr. A.
Jahn, a topographic engineer residing in Caracas, Lake Val-
encia drains through the Rio Pao, a tributary of the Orinoco,
in the rainy season, but during the long dry season water
often flows from the river into the lake. Dr. Jahn stated that
the surface of the lake has varied from 412 M. to 415 M.
above sea level during the past twenty years. He said that
he had made extensive soundings and found the greatest depth
to be about fifty meters. The lake is about fifty kilometers
long.

Lake Valencia contains twenty-two islands, the shores of
which are for the most part rocky, pebbly, or sandy (Fig. 2).
The largest, Isla del Euro, is about five kilometers long. The

8

UNIVERSITY OF WISCONSIN STUDIES

importance of means for dispersal and isolation are shown by
the fact that there are no frogs or snakes on Isla del Euro while
another island (Culebra) in the lake is so heavily infested with
poisonous snakes that the natives avoid it.

In order to gain some idea of general conditions in Lake
Valencia a few limnological observations were made. Table I

FIG. 2. Shore of Isla del Euro and tishing crew.

TABLE I

Temperature and gases (determined by the Winkler method) at various
depths in Lake Valencia July 17, 1918. Gases are given in c.c. per liter at 0°
— indicates that the water was alkaline as judged by phenapthaline titration

with -TJQ sulphuric acid solution. The depth of the water where samples were
taken was 26 m.

Depth

Temperature

Oxygen, c.c. per liter

Carbon diox., c.c.
per liter

0.5
1

27.6

27 5

4.897

2

27 25

3

27.25

4

27.2

5
7.5

27.2
27 16

4.792

-14.2

10

27 15

4 735

12 5

27 15

15
20

25

27.15
27.01
26.85

4.872
4.755
4.435

-14.2
-9.77
-9.77

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA

TABLE II

Catches with mud dredge at various depths in Lake Valencia, July 18,
1918. Under "number" the figure in parentheses indicates the individuals (n)
actually caught in two hauls of the dredge; the figure following indicates the

44 44

number per square meter (n X —^ — )• Figures under "volume" indicate per-
centage by volume of total catch after mud had been washed out through
bolting cloth having 10 meshes per c.m.

Depth

Organism

Number

Volume

4.7m

Fish scales

(123)
(78)
(2)
(1)
(1)
(1)
(1)

(3895)

2733
1733
45
22
22
22
22

86547

2
2
3
.1
1
.2
.1

52.6
40

Chironomus larva,

Perithemis? nymph

Insect larva . .

Corixa nymph

Arrhenurus

Leech
Planorbis pronus Mts., Ancylus moricaud
Orb., A. sp.? Amnicola valenciae Prest.*
Potamopyrgus crystallinus Pfr., andAmni
cola ernesti Mts

Plant remains

9.6m

Fish scales . .

(80)
(3)

(25700)

1778
67

571054

1

12

85
2

Physa venezuelensis Mts

Amnicola valenciae Prest., Potamopyrgus
crystallinus Pfr., and Amnicola ernesti Mts,
Filamentous algae

15 m

Symbranchus marmoralus
Fish scales
Planorbis pronus Mts
Amnicola valenciae Prest., Potamopyrgus
crystallinus Pfr., and Amnicola ernesti Mts

(1)
(2)
(4)

(6304)

22
45
89

140075

8
.2
.3

91.5

20 m

Fish scales

(3)
(1)
(671)
(4)

(-235)

(3800)
(1)

67
22
14909
89

5221

84436
22

.3
.2
60

.2

15

24.2
.1

T any pus larva

Planorbis pronus Mts., shells

Planorbis pronus Mts., alive. . .

Amnicola valenciae Prest. and Potamopyrgus
coronatus Pfr alive

Amnicola valenciae Prest., Potamopyrgus
crystallinus Ph., and Amnicola ernesti Mts..
shells

Ancylus moricaudi Orb., shell

26 m

Hoplias malabaricus scales
Planorbis pronus Mts., shells

(3)
(107)
(5)

(22)

(5400)

(2)

67
2378
111

489

119988
44

.3
3
1

1

93.4
.3
1

Planorbis pronus Mts., alive. .

Amnicola valenciae Prest. and Potamopyrgus
crystallinus Pfr., alive. . . .

Amnicola valenciae Prest., Potamopyrgus
crystallinus Pfr. and A mnicola ernesti Mts..
shells

Ancylus moricaudi Orb., shells
Plant remains

* According to Mr. Bryant Walker this species was described as an Amnicola, but is more
likely a Potamopyrgus.

10 UNIVERSITY OF WISCONSIN STUDIES

shows the temperatures and the gaseous contents of the water
at various depths. The lower temperature of the deeper water,
with the decrease in oxygen and increase in carbon-dioxide,
indicates a stratified condition. However, there was an abun-
dance of oxygen for fishes at all depths. A Secchi disc 20 cm.
in diameter at 10:45 A.M. in bright sunlight disappeared at
3.5 meters, July 18.

Catches with fine (18 mesh per cm.) and coarse (10 mesh)
tow nets in deep and in shallow water indicated that plankton
was not very abundant. Practically nothing was caught in
the coarse net; the fine one yielded some Diaptomus, Cyclops,
considerable numbers of Moinodaphnia, and a few algae.

Hauls with Juday's (1916) improved Ekman mud dredge
were more productive of results. The dredge used was of
brass and cubical in form. It took samples of the bottom to
a depth of 15 cm. over an area 15X15 cm. Table II gives the
results of ten hauls made at various depths on July 18. It will
be seen that the midge larvae, so characteristic in temperate
regions of deep lakes with muddy bottoms, are largely replaced
by snails. Most of the snails were of small size and the catches
after they had been freed from mud consisted largely of
"dead" snail shells. A young eel (Symbranchus marmoratus)
caught at a depth of fifteen meters was placed in a bottle with
bottom mud and water. It at once burrowed into the mud
but in a few minutes protruded its head and kept it out. On
July 25 thirty hauls were made with the dredge where the water
was 14.2 M. deep and another small eel was thus secured. A
thorough study of the bottom of Lake Valencia would doubtless
add to the known fauna, but the data presented in Table II is
indicative of the general conditions. It will be noticed that
snails are very abundant in deep water. Systematic and
extensive use of a mud dredge in the lake would doubtless give
interesting results relating to the ecological distribution of the
different species.

Reviewing the conditions afforded by Lake Valencia as an
environment for fishes it may be said to be a tropical lake with
muddy bottom and receding shore line. The water is of average
turbidity and hardness. Distinctive habitats are the muddy
bottom in deep water; the sandy, pebbly, and rocky shores
of the islands; the rush-grown shores about the margin of the
lake, and the mouths of rivers where emergent plants other than
rushes are found.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 11

LIST OF FISHES WITH REMARKS ON GEOGRAPHICAL
AND ECOLOGICAL RELATIONSHIPS

Professor C. H. Eigenmann (1920) lists twenty-three species
of fishes from the Valencia basin. These fall into four groups
according to their geographic distribution. In the following
list colloquial names follow scientific names when they are
known:

(1) Species widely distributed in South America:
Rhamdia quelen Quoy & Gaimard — bagre.
Plecostomus plecostomus Linnaeus — panaque.
Hoplias malabaricus (Bloch) — guabina.
Astyanax bimaculatus (Linnaeus) — sardina.
Gymnotus carapo Linnaeus — lamprea.
Symbranchus marmoratus Bloch — anguila.

(2) Species found in Trinidad:

Chorydoras aeneus Gill — plated nematognath.
Curimatus argenteus Gill — cula.
Odontostilbe pulcher (Gill) — sardina.
Lebistes reticulatus (Peters) — sardina.
Aquidens pulcher (Gill) — chusco.

(3) Species ranging through Venezuela, Rio Meta, and
probably elsewhere.

Pimelodella metae Eigenmann — bagre.
Pimelodella tapatotoe Eigenmann — bagre.
Cochliodon plecostomoides Eigenmann — panaque.
Chaetostomus pearsei Eigenmann — coroncho.
Chaetostomus guarensis Steind. — coroncho.
Chaetostomus nudirostris Liitken.
Moenkhausia pittieri Eigenmann — sardina.
Astyanax metae Eigenmann — rabo de candela.
Gephyrocharax valenciae Eigenmann — sardina.
Menidia venezulae Eigenmann.
Crenicichla geayi Pellegrin — mataguaro.

(4) Species found in the lake itself. All but two species
are also found in Classes 1 and 3. Hemigrammus marginatus

12 UNIVERSITY OF WISCONSIN STUDIES

is also found in Southern Brazil; Creagrutus beni ranges along
the base of the Cordilleras from Bolivia to Caracas.

Plecostomus plecostomus Linnaeus — panaque.

Hoplias malabaricus (Bloch) — guabina.

Hemigrammus marginatus Ellis — sardina.

Astyanax bimaculatus (Linnaeus) — sardina.

Gephyrocharax valenciae Eigenmann — sardina.

Creagrutus beni Eigenmann — sardina.

Lebistes reticulatus (Peters) — sardina (top minnow).

Symbranchus marmoratus Bloch — anguila.

Crenicichla geayi Pellegrin — mataguaro.

Aquidens pulcher (Gill) — chusco.

Of the twenty-three species listed, seventeen are widely
distributed or indigenous. Five other species are also found
in Trinidad. The geographical relationship of the fish fauna
of Lake Valencia and its tributaries is largely with the territory
toward the east.

Fifteen of the species were collected in rivers, and five of
these were found in no other habitat. Thirteen species were
taken at the mouths of rivers and two of these were not found
elsewhere except in rivers. Ten species were found along the
shores of the islands in Lake Valencia; seven in and near the
rushes about the margin of the lake; four species in the deeper
parts of the lake. Three species found in rivers were found
nowhere else except on the shores of the islands. Four of the
species present in the lake were not collected in rivers; eleven
of those from rivers were not found in lakes. The three species
found in all habitats (Hoplias malabaricus, Astyanax bimacu-
latus, Symbranchus marmoratus) are widely distributed geo-
graphically. Aquidens pulcher, another widely distributed
species, was found in all habitats except rivers.

The facts described in the last paragraph may be taken to
mean that the river is the oldest habitat and the lake the
newest for the fishes in this region, because the former contains
the larger number of species. This view is supported by the
fact that toward the east, where the geographical affinities of
these fishes lie, there are practically no lake habitats and many
rivers.

The same facts may be interpreted as indicating that,
because a river contains a greater variety of conditions (habitats),

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 13

there is opportunity for more species to live in it. The lake,
being more uniform as to conditions, contains fewer species.
This view is supported by the ecological distribution of the
fishes in the lake. The habitats have species in direct ratio
to the variety of conditions they possess — ten species frequent
the shores of the islands; seven occur on the rush covered mud
bottom about the margin of the lake; only four are found on
the soft ooze in deep water.

Fishes unquestionably choose particular habitats which in
general suit their particular needs. The mataguaro, panaque,
and a sardina (Hemigrammus marginatus) were found in
turbulent water formations (on the sandy and pebbly shores
of islands, in the swift flowing streams), never on muddy
bottoms or in quiet water. The chusco (Aquidens pulcher)
occurred wherever there were muddy bottoms and quiet
water and, as both these conditions were lacking in the swift
flowing streams draining into Lake Valencia, the species is
confined to the lake itself. Two sardinas, Gephyrocharax
valenciae and Creagrutus beni, and a top minnow, Lebistes
reticulatus, were found only at the mouths of or in streams.
The sardina, Gephyrocharax valenciae, was abundant along the
shores of islands and along the rushes on the lake's margin, but
was never found in streams or in deep water. Another sardina,
Creagrutus beni, was common along the shores of Isla del Euro,
but was not found on muddy rush-grown shores.

The fishes invading all habitats are those in general having
a wide range geographically. Among the three examined
intensively at Lake Valencia, the guabina is a fish-eater (90
per cent); the sardina, Astyanax bimaculatus, feeds on plants
(51), insects (30), and fish (15); the anguila eats insects (63),
bottom deposits (22), and fish; the chusco, common in all lake
habitats, partook largely of snails (49), insects (22), and fish
(16). Although these four species are more or less specialized
in their food habits, they feed on common ubiquitous foods.
The two other species (Rhamdia quelen and Plecostomus
plecostomus) of wide geographic range which occur in the
Valencia region are largely associated with rivers, but feed on
ubiquitous mud and insects. Ecologically the ability of a
species to extend over a wide range depends upon an abundant
food supply and the ability to invade a variety of habitats.

14

UNIVERSITY OF WISCONSIN STUDIES

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PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 15

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16 UNIVERSITY OF WISCONSIN STUDIES

The latter conclusion is clearly indicated by the fact that
two-thirds of all the species with wide geographic ranges
invade every habitat in the lake, while none of the species
with limited geographic ranges are found in all habitats. The
species confined to rivers are not restricted in habitat, except
that they are confined more or less to turbulent water forma-
tions. The cula is a mud eater and hence has an ubiquitous
food but is limited in range and in ecological distribution,
ranging geographically through Trinidad and the Valencia
basin and being limited ecologically to the rushes along the
lake shore and to the streams. The coroncho is still more
limited in geographic range and is restricted ecologically to
swift streams which contain large boulders. It clings to the
under side of rocks and subsists entirely on the fine muddy
deposits which collect in the eddies.

Perhaps enough has been said to bring out the point the
writer wishes to make; a wide-ranging species usually feeds
upon an ubiquitous food and is often able to invade a number
of habitats; species with a limited geographic range are limited
ecologically in food, habitat, or both. The fishes discussed
in this paper illustrate this principle very well. Shelford (1911)
relates the activities of fishes to the law of minimum and
says, "the activity which determines the range of conditions
under which a species will be successful is the activity which
takes place within the narrowest limits." He also points out
that "centers of origin" are sometimes only places where
optimum conditions for a number of species exist. The writer
would emphasize the view that, without other evidence, the
fact that a species had a wide range would not necessarily be
taken as indication that it was older than an associated species
with a restricted range, as geographers have sometimes asserted.
The ecology of each species would have to be considered with
its range before making generalizations.

Tables III and IV show the catches made in gill nets.
These are arranged so as to compare the four chief habitats in
the lake: (1) the shores of the islands, which were rocky,
pebbly, or sandy, and at the heads of bays sometimes a little
marshy; (2) the marshy, rush grown shores around the margin
of the lake; (3) the mouths of streams; (4) the deep water.
The catch per hour in gill nets is a good means of determining

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA

17

TABLE IV

Total catches at all depths and localities with nets of different sized meshes.
The figures give the total catch and the catch per hour.

tfl

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110-41

45-. 41

19-. 17

43-. 39

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50-. 45

4-. 04

i

249-7

79-. 32

3-. 01

136-.55

0-0

29-. 12

0-0

2

167-10

27-. 16

0-0

0-0

1-.006

0-0

0-0

3

167-33

0-0

0-0

0-0

0-0

0-0

0-0

the abundance, size, and variety of fishes present at different
localities. The method has some apparent defects — the most
active species are most often caught, species too small to
become entangled in the finest meshes are not caught at all,
and some fishes (catfishes, eels) without hard exoskeletal parts
are seldom caught. The results tabulated lead to the following
conclusions: There are few or no large fishes in the lake,
because nothing was ever caught in the 3-inch mesh nets. The
guabina (Hoplias malar abicus) is the largest and most active
fish in the lake. It has a close rival numerically in the chusco
(A quid ens pulcher). The mataguaro (Crenicichla geayi) is
rare in the lake or moves about very little, probably the
former is true for it was seldom caught in seines. The total
catch of fishes per hour is far below those sometimes made in
some lakes in the United States. In Lake Mendota, for exam-
ple, the average number of perch caught was sometimes over
a hundred in twenty-four hours for a 1 in. mesh set in deep
water during the summer.

The gaubina and a sardina, Astyanax bimaculatus, are found
in all habitats. There are more fishes and species along the
shores than in deep water, but one species, the chusco, appears
to be more abundant at greater depths. The chusco is a mud-
bottom species, is least abundant on the shores of islands, and
is not found in rivers. The mataguaro, on the other hand, is
typically a river fish and is found in the lake only in the turbu-
lent water formations along the shores of the islands.

There is perhaps a migration of the smaller fishes into
deeper water during the day. This is indicated by the fact
that seining along shore was much more productive at night.

18 UNIVERSITY OF WISCONSIN STUDIES

FOOD OF FISHES

It was the plan to study the food of ten individuals of each
species from each habitat in the lake. The following review
does not include food notes on all the fishes collected in the
Valencia basin but gives a good idea of all the common species
in the lake itself. Table V summarizes the results. In the
table and in the following notes lengths are given in millimeters
and do not include the tail fin. Numbers relating to foods
mean percentage by volume. In making examinations for
food the contents of the stomach and intestine were stripped
on a glass plate, the entire alimentary canal was then slit open
and any remaining materials taken. The food mass was teased
with needles under a binocular microscope, any small objects
being examined under a compound microscope.

Aquidens pulcher (Gill), Chusco

Isla del Euro; July 9, 10; number examined, 10; lengths,
105-62, ave. 97. Food: undetermined insect larvae 3.5;
chironomid larvae .9; chironomid pupae .1; fly 2; ostracods 9.5;
snails 83.5.

Off rush-grown shore, 2.5 m., Maracay; July 22; no. ex., 5;
lengths 106-73, ave. 97. Food: fish 20; undetermined insect
larvae 19; chironomid larvae 9; ostracods .6; snails 45.4;
plants 6.

Off rush-grown shore, Maracay, July 28, 12 m.; no. ex., 3;
lengths 90, 74, 77; ave. 80. Food: fish 42; chironomid larvae
28; ostracods 10; snails 20.

Off rush-grown shore, Maracay, July 26; no. ex., 3; lengths
80, 80, 103, ave. 88. Food: fish 10; Tanypus larvae 35;
Tanytarsus larvae 5; Orthocladius larvae 1.7; snails 18.3;
plants 8.3; bottom 21.7.

Mouth of Rio Bue, July 19, no. ex., 4 (2 empty); lengths
128-112, ave. 120. Food: fish 50; insects 50.

Summary — No. ex. 24; ave. length 92. Food: fish 16.3;
undetermined insect larvae 10.4; chironomid larvae 12; chirono-

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 19

mid pupae + ; fly .9; ostracods 5.8; snails 49; plants 2.5;
bottom mud 3.

The chusco feeds on muddy bottoms upon the most abun-
dant foods — snails constituting the chief item in its dietary.

Astyanax bimaculatus (Linnaeaus), Sardina

This large sardina was found in all parts of the lake, but
was most abundant near the islands.

Isla del Euro, 2 m., July 9; number examined, 1; length 95.
Food: midge pupae 30; cladocerans 30; plants 20; plankton
algae 20.

Isla del Euro, 11 m.; July 10; no. ex., 3; lengths: 120, 105,
109, ave. 108. Food: fish 33.3; midge pupae 12; plants 8;
plankton algae 46.7.

Isla del Euro, 7 m., July 10; no. ex., 3; lengths 106, 92, 89,
ave. 96. Food: fish 15; Sialis nymph 3; insects 13; snail eggs
1; plants 20; Wolffia 7; algae 10.

Isla del Euro, 11 m., July 10; no. ex., 1; length 96. Food:
fish 35; fly 25; plants 35.

Isla del Euro, 1.5 m., July 10; no. ex. 2; length 96, 90. Food:
plants 40; plankton algae 60.

Mouth of Rio Bue, July 19, no. ex., 2; lengths 28, 32. Food:
insect remains 100.

Mouth of Rio Bue, July 20; no. ex., 2; length 78, 85. Food:
unknown 50; insects 35; algae 15.

Off rush-grown shore, 12 m., July 28; no. ex., 3, length 95.
Food (2 empty): insect nymph 2; plants 60, algae 38.

This is the largest "sardina" found in Lake Valencia and
more than half of its food consists of vegetation, including
plankton. It therefore goes back to the fundamental sources
of food in the lake for its energy and in turn serves as food for
caimans, cormorants, herons, and predacious fishes.

Astyanax metae Eigenmann, Sardina

Rio Castano, July 27; number examined, 4; length 116-79,
ave. 97. Food: may fly nymphs 45; plant remains 49; seeds 6.

These four specimens were examined in order to compare
another species in the same genus with the last. Although
this species was confined to rivers, its food was much the same
as that of its relative in the lake — more than half vegetation.

20 UNIVERSITY OF WISCONSIN STUDIES

Chaetostomus pearsei Eigenmann, Coroncho

Rio Castaiio, July 16; number examined, 10; lengths 111-86,
ave. 93. Food: bottom mud and sand, 100.

This sucker-like catfish lives in the swift boulder-filled
streams with sandy bottoms. It clings to the under side of
rocks by means of its mouth and feeds largely on bottom mud.

Creagrutus beni Eigenmann, Sardina

Isla del Euro, July 12; number examined, 10; lengths 32-25,
ave. 28. Food: midge pupae 3.8; snails 96.2.

This little sardina, caught on the same beach as the Astyanax
bimactdatus taken in this locality, had eaten quite different
foods.

Crenidchla geayi Pellegrin, Mataguaro

Isla del Euro, 2 m., July 9; number examined, 5; lengths:
146-130, ave. 139. Food: fish 10.5; snails 52; Planorbis 37.5.

Isla del Euro, 11 m., July 10; no. ex., 2; lengths: 126, 135.
Food: (1 empty) fish 100.

Isla del Euro, 7 m., July 10; no. ex., 2; lengths: 147, 148.
Food: snails 100.

Rio Castaiio, July 27; no. ex., 2; lengths 159, 56. Food:
unidentified insect larvae 90; chironomid larvae 10.

This fish feeds largely on snails, fishes, and insect larvae.

FIG. 3. The cula, cnrhnalus argenlem

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA

21

Curimatus argenteus Gill, Cula

Mouth of Rio Bue, July 19; number examined, 5; lengths
107-88, ave. 98. Food: fine organic sediment and mud 100.

Rush-grown shore, Maracay, July 22, no. ex., 2; lengths
102, 93. Food: algae, some filamentous blue greens, 99.5;
ostracod .5.

This species has a very long coiled intestine (Figs. 3, 4)
and a gizzard at the posterior end of the stomach. It apparently
subsists mostly on mud and algae.

FIG. 4. A cula opened to show the coiled intestine.

Gephyrocharax valenciae Eigenmann, Sardina
Mouth of Rio Bue, July 20; number examined, 10; lengths
40-30, ave. 37. Food: undetermined insect larvae 10;,
chironomid larvae 1; chironomid pupae 6; cladocerans 5.5;
cyclops 5.5; ostracods 1.1; mites 1.5; plants 14; algae 21.4; fine
sediment 12.5; unknown 21.5.

Rush-grown shore, Maracay, July 24; no. ex., 10; lengths
39-30, ave. 33. Food: undetermined insects 12.5; water bug
5.5; beetle 8; ants 29.5; mites .5; eggs (snail or amphibian?) 40;
plants 7.2; unknown 4.

This sardina is versatile in its food habits. It is probably
the most abundant fish in Lake Valencia. It occurs in enormous
numbers along all shores but is most common over muddy
bottoms. It serves as food for many other animals — such as
herons, cormorants, gulls, caimans, and predacious fishes.

Hoplias malabaricus Bloch, Guabina

Isla del Buro, 3 m., July 9; number examined, 2; lengths:
155, 160. Food: fish 95, eggs 5.

22 UNIVERSITY OF WISCONSIN STUDIES

Isla del Euro, 9 m., July 10; no. ex., 2; lengths: 205, 200.
Food; fish 100.

Isla del Euro, 7 m., July 10; no. ex., 1; length 153. Food:
fish 100.

Isla del Euro, 15 m., July 10; no. ex., 1; length 90. Food:
plankton algae 100.

Isla del Euro, 5 m., rocky shore, July 10; no. ex., 5; lengths
305-186, ave. 233. Food: fish 48.3; 8 sardirfas (40-55 mm.
long) 33.3; dragon-fly nymphs (close to Perithemis). 18.3.

Reed-grown shore, Maracay, 2 m., July 22; no. ex., 2;
lengths 263, 212. Food: fish 32.5; eel (Symbranchus, 60 mm.
long) 50; 2 damsel-fly larvae 12.5; gelatinous algae 5.

Reed-grown shore, Maracay, 1.5 m., July 23; no. ex., 8;
lengths 370-189, ave. 222. Food : fish 90, Sialis-like insect 10.

Off rush-grown shore, mud bottom, Maracay, 12 m., July 28;
no. ex., 8; lengths 399 (1.37 kilos)— 139, ave. 251. Food:
none.

This was the largest species of fish found in Lake Valencia.
The guabina is a fierce, predacious creature with sharp, strong
teeth. It ranges through all available habitats for its chief
foods — fishes (90) and insects. When gill nets were pulled
once every twenty-four hours the guabina were often empty of
food, indicating that digestion is rapid.

Lebistes reticulatus Peters, Sardina

Isla del Euro, 1 m., July 11; number examined 10; lengths
21-14, ave. 16.4. Food: algae 96.1; Diptera 3.9.

Rush-grown shore, Maracay, 5 m., no. ex., 10; lengths
30-13.5, ave. 21. Food: Cyclops 11.1; cladocerans 2.2;
ostracods 6.1; rotifers 2.6; algae 78.

This little top-minnow feeds mostly on algae and plankton
animals. It is very hardy and lived for hours in collecting pails
after other fishes were dead.

Pimelodella metae Eigenmann, Eagre

Mouth of Rio Bue, July 29; number examined 10; lengths
79-37, ave. 61. Food: fish 8.3; insect larvae 7.3; chironomid
larvae 8; may-fly nymphs 23; damsel-fly nymphs 8.5; caddis-fly
larvae 1.5; beetle larvae 6.5; chironomid pupae 7.5; ostracods
.7; earthworm 14.5; plant .2; mud and debris 13.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 23

Like many catfishes, this little bagre is versatile in its food
habits.

Plecostomus plecostomus Linnaeus, Panaque

Isla del Euro, 9 m., off sandy shore; number examined 1;
length 283. Food: ostracods 5; sponge spicules 20; remains
of "old" plants 10; diatoms 10; filamentous algae 1; fine
bottom sediment 54.

This fish usually lives in rivers and the Venezuelans were
greatly surprised to see it in the lake. It apparently feeds
largely on fine bottom mud.

Rhamdia quelen Quoy & Gaimard, Bagre

Rio Castano, under rocks, July 27; number examined 3;
lengths 155, 150, 62. Food: chironomid larvae 46.6; grass-
hopper 20; Sphaeridae 3.3; fine bottom debris 30.

•^.

Symbranchus marmoratus Bloch, Anguila

Isla del Euro, among rocks, July 9; number examined 3;
lengths 320, 240, 172. Food: Sialis larva 98; sand 2.

Isla del Euro, among rocks, July 11; no. ex. 3; lengths 301,
150, 138. Food: fish 12; chironomid larvae 5; caddis-fly
larvae 72; insects 11.

Isla del Euro, among rocks, July 12; no. ex., 5, lengths
272-150; ave. 233. Food: caddis-fly larvae 33.3; undeter-
mined insect larvae 43.3; sand and pebbles 23.3.

Caught in mud dredge, off Maracay, 14.5 m.; July 25;
no. ex. 1 ; length 130. Food: the top layer of the bottom ooze
100.

Young eels apparently live buried in the bottom mud in
both deep and shallow water. The adults subsist largely on
insects.

24

UNIVERSITY OF WISCONSIN STUDIES

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26 UNIVERSITY OF WISCONSIN STUDIES

GENERAL REMARKS ON FOOD

Table V shows that the foods eaten by the fourteen im-
portant species of fishes in Lake Valencia rank as follows, the
figures indicating the average percentage by volume for all
species: mud 27, snails 12.4, algae 11.8, fish 10.3, plants 6.6,
unidentified insect larvae 5.3, chironomid larvae 5.1, may-fly
nymphs 4.9, unidentified insects 2.8, caddis-fly larvae 2.4,
chironomid pupae 2, ostracods 1.7, unidentified eggs 1.5,
sponges 1.4, grasshopper 1.4, Diptera 1.3, sand 1.3, unidentified
food 1.2, earthworm 1.1, ants 1, damsel-fly nymphs .7, copepods
.6, beetle larvae .5, cladocerans .4, seeds .4, dragon-fly nymphs
.3, pebbles .3, Sphaeridae .3, beetles .3, bugs .2, Sialis larvae
.1, mites .1, rotifers .1.

If the foods are collected into larger groups the order is
as follows: mud, sand, and pebbles, 28.6; immature insects,
19.3; plants, 18.8; molluscs, 12.7; fish, 10.3; adult insects, 7;
entomostracans^ 2.7 ; chironomid pupae, 2; unidentified eggs,
1.5; sponges, 1.4; unidentified food, 1.2; earthworm, 1.1; mites,
.1; rotifers, .1.

The fishes feeding on particular foods are as follows:

FISHES: Hoplias malabaricus 90, Aquidens pulcher 16, Cre-
nicichla geayi 15, Astyanax bimaculatus 11, Pimelodella
metae 8.3, Symbranchus marmoratus 4.5.

INSECTS AND LARVAE : Symbranchus marmoratus 72.9, Rhamdia
quelen 67; Pimelodella metae 62.3, Astyanax metae 45,
Gephyrocharax valenciae 35.1, Astyanax bimaculatus 24.2,
Aquidens pulcher 23, Lebistes reticulatus 18, Crenicichla
geayi 17.7; Creagrutus beni 14, Hoplias malabaricus 8.4.

ENTOMOSTRACA: Lebistes reticulatus 9.1, Creagrutus beni 7.8,
Aquidens pulcher 6, Astyanax bimaculatus .7, Plecostomus
plecostomus .5, Curimatus argenteus .1.

MOLLUSCS: Creagrutus beni 78, Aquidens pulcher 49, Cre-
nicichla geayi 47, Rhamdia quelen 3.3, Astyanax bimaculatus 2.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 27

PLANTS: Lebistes reticulatus 87, Astyanax metae 55, Astyanax
bimaculatus 52, Curimatus argenteus .28, Plecostomus ple-
costomus 21, Gephyrocharax valenciae 15.3, Aquidens pulcher
2.5, Hoplias malabaricus .8, Pimelodella metae .2.

MUD: Chaetostomus pearsei 100, (young Symbranchus mar-
moratus from bottom of lake 100), Curimatus argenteus
71, Plecostomus plecostomus 54, Rhamdia quelen 30, Syw-
branchus mar moratus 22, Pimelodella metae 13, Gephyro-
charax valenciae 6.3, Aquidens pulcher 3.

These lists and the data presented in Table V indicate
clearly that bottom sediment, insects, plants, molluscs, and
fishes are the most important foods for the fishes of Lake
Valencia. Plankton, plant or animal, is not important, but the
bottom fauna is a valuable source of food for several species.
The fishes feeding on plants are small, abundant species which
often themselves serve as food for fish eating animals. The
snails and a portion of the immature insects also pass on
organic food acquired from plants to predacious animals when
they are eaten. The great reservoirs of food available for
fishes are the bottom mud (where the organic compounds are
derived from plants and to some extent from animals), the
aquatic vegetation, and the abundant small animals (snails,
insect larvae, etc.) feeding directly or indirectly on plants, mud,
and to a less extent on other animals.

It is probable that this condition is not unusual in lakes,
tropical and otherwise. The aquatic vegetation and bottom
deposits are usually more important sources of fish food than
the plankton. Petersen (1918) has come to the same con-
clusions in regard to the ocean.

28 UNIVERSITY OF WISCONSIN STUDIES

PARASITES OF VALENCIAN FISHES

The following list gives the names of all parasites identified
and also mentions a few of uncertain relationships. The
latter are necessarily included in the statistical comparisons.
The Acanthocephala have already been described by Dr. H. J.
Van Cleave and the nematodes are to be worked up by Dr. N. A.
Cobb. Drs. M. J. Rathbun and B. H. Ransom read the
portions of the manuscript relating to the new species of
parasites and made many helpful suggestions.

BACTERIA

The liver of a sardina, Astyanax bimaculatus (L.), collected
in Lake Valencia near Maracay, July 22, 1918 was one mass of
cysts. It was sent to Professor H. S. Davis who said:

"The cysts from sardina 116 are very interesting. I have
been unable to find any trace of Sporozoa but sections show
the presence of exceptionally large rod-shaped bacteria which
are probably the cause of the cysts. It is apparently an
undescribed disease."

Cysts, probably caused by the same organisms, were found
on the stomach of a gaubina, Hoplias malabaricus Bloch,
caught by the Isla del Buro, July 11.

TREMATODA
Genus Parspina, new

Body broad, flat; with twenty spines of equal size sym-
metrically arranged about the mouth. Uterus long, coiled
in anterior end of posterior half of body; testes on either side
at posterior third of body, elongate, slightly lobate; ovary
spherical, anterior to uterus near median line; vitelline glands
on either side of body, anterior to uterus. Intestinal rami
smooth, extending from posterior end of anterior quarter to
beginning of posterior seventh of body; oral sucker deep but
mouth small; a slender prepharynx present; pharynx spherical.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 29

The general plan of structure resembles that of the genus
Pneumatopliilus Odhner but the spines about the mouth are
different. Type species — Parspina bagre.

Parspina bagre, new species

Length of body, .63 mm.; width, .37 mm.; widest a little
behind middle. Cuticula without spines. Oral sucker, deep;
length, nearly one-fifth that of body; surrounded by twenty
symmetrically arranged blunt, straight hooks of equal size.
Prepharynx short and slender. Pharynx globular; nearly half
as long as oral sucker. Intestinal rami branching directly from
pharynx; smooth; extending to the posterior seventh of the
body. Diameter of acetabulum a little less than that of oral
sucker.

The genital field, without the vitellaria, occupies the
posterior half of the body. The two testes lie side by side,
the left slightly anterior to the right, about one-third of the
body length from the posterior end. They are ovate, slightly
lobate, and the left is somewhat smaller than the right. The
ovary is spherical. It lies a little posterior to the acetabulum
and slightly toward the right of the median line. Its diameter
is one-fourteenth the length of the body. Cirrus pouch almost
as wide as the acetabulum, from which it extends posteriorly
and to the left. Vitellaria grouped around the intestinal rami,
in the second fourth of the body, extending from the uterus to
the pharynx. Uterus, slender, coiled in posterior half of the
body, containing many eggs. Size of eggs, .016 by .008 mm.
Excretory system Y-shaped, without large terminal bladder.

Host: bagre (catfish), Pimelodella metae Eigenmann, in
intestine.

Type: Cat. No. 7575 (Helminthological Collection, U. S.
National Museum). Collected at the mouth of the Rio Bue,
near Maracay, Lake Valencia, Venezuela, July 29, 1918. Two
specimens were found in a single catfish.

Cysts which contain a larva, apparently of this species,
were often found in the fins of small fishes. Figure 5 (Cat.
No. 7577; Helm. Coll. U. S. N. M.) shows a cyst from the
pectoral fin of a mataguaro, Crenicichla geayi Pellegrin, collected
by the Isla del Euro, July 9, 1918. The wall of this cyst is
thin and its entire length is .22 mm. There is some space

30

UNIVERSITY OF WISCONSIN STUDIES

FIG. 5. Parspina bagre. The upper figure shows an adult; the lower figure,
an encysted larva.

between the wall of the cyst and the larva within. The
larva is elliptical. Its anterior end is truncated and
armed with twenty spines. The interior of its body shows no
differentiation into organs but is filled with coarse granules.
Larvae like those represented in Figure 5 were also found in
the fins of the following fishes: cula, Curimatus argenteus
Eigerwnann; the sardinas, Astyanax bimaculatus (L.), Creagrutus
beni Eigenmann, and Gephyrocharax valenciae Eigenmann; the
top-minnow, Lebistes reticulatus (Peters).

The distribution of cysts in the fins is characteristic. Ten
Creagrutus beni collected near the Isla del Euro, July 12, had
cysts distributed on the fins as follows: dorsal 37, caudal 31,
anal 20, pelvic 17, pectoral 15, skin 1. Ten Gephyrocharax
valenciae collected at the mouth of the Rio Bue, July 20, gave
the following results: caudal 41, anal 32, dorsal 17, pelvic 5,

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 31

pectoral 3. The cysts are more abundant toward the posterior
end of the body.

Genus Wallinia, new

Plagiorchiidae with the genital pore median and immediately
anterior to acetabulum; vitellaria small and largely confined to
the lateral regions of the second quarter of the body; aceta-
bulum one-fourth to one-third greater in diameter than the
oral sucker, situated close behind the bifurcation of the intes-
tinal rami; ovary globular, small, on the left side behind the
acetabulum; testes rounded, arranged one behind the other
in the third quarter of the body, the posterior one somewhat
to the left of the median line, Named for Dr. Ivan E. Wallin.

This genus differs from Pneumonoeces in the position of the
genital opening, the size and position of the acetabulum, and
from Plagiorchis in the arrangement of vitellaria, acetabulum,
testes, and other features. Type species — Wallinia valenciae.

Wallinia valenciae, new species

Length, 1.34 mm. (contracted); width, .38; body widest in
region of acetabulum, constricted behind the oral sucker
(Fig. 6). Diameter of acetabulum about one-fifth the length
of the body; diameter oral sucker about two thirds that of

FIG. 6. Wallinia valenciae.

acetabulum. Genital field occupies the posterior three-fourths
of the body. The small spherical ovary lies somewhat' behind
the acetabulum on the left side. The testes are rounded; the
anterior one lies slightly behind the ovary near the median
line; the posterior testis is on the left side of the body, extending
to the middle of the intestinal ramus on that side. The uterus
is coiled in the posterior three-fourths of the body; the loops
are slender and filled with eggs. Size of eggs, .041 by .02 mm.

32

UNIVERSITY OF WISCONSIN STUDIES

The vitellaria are small and lie outside the intestinal rami in
the second quarter of the body. The genital pore is crowded
into the triangular space between the anterior margin of the
acetabulum and the intestinal rami.

Host: Gephyrocharax valenciae Eigenmann, in intestine.

Type, Cat. No. 7569 (Helm. Coll. U. S. N. M); collected
from a fish taken in Lake Valencia at Maracay, in shallow
water among rushes, July 24, 1918.

The following species is placed in the genus Allocreadium
Looss, although it appears to differ from other members of
that genus in possessing a shorter esophagus and in the position
of the genital aperture immediately anterior to the acetabulum.

Allocreadium wallini, new species

Length, 1.55 mm.; width, .74 mm.; body widest behind
middle (Fig. 7). Oral sucker and acetabulum approximately
equal in diameter. Ratio of diameter of oral sucker to that of
pharynx about 7:3. A short prepharynx is present. Intestinal
rami smooth, branching directly from pharynx, extending to
posterior fifth of body. Cuticula is without spines.

FIG. 7. Allocreadium wallini. A, a young individual; B, a mature individual
with eggs in the uterus.

PEARSE FISHES OF LAKE VALENCIA, VENEZUELA

The genital field, without vitellaria, occupies nearly half
the length of the body and the posterior testis is one-fifth the
body length from the posterior end. The spherical ovary lies
on the right side of the body at the posterior margin of the
acetabulurn; diameter about one-fifteenth the length of the
body. The lobate testes are about twice the diameter of the
ovary. They are usually close together between the intestinal
rami, are usually elongated across the body, and one lies anterior
to the other. Vitellaria, small, rounded, filling the body
posterior to the testes and distributed anteriorly along the
sides to points just anterior to the acetabulum. The folds of
the uterus are very large. It is coiled on the left, side of the
body in the region of the acetabulum, and usually contains a
few (0-29; average 5) eggs (.15 mm. long). Cirrus sac elongated,
pear shaped, nearly as long as the diameter of the acetabulum.
Genital pore anterior to margin of acetabulum and slightly
to the right of the median line.

Host: Mataguaro, Crenicichla geayi, in intestine.

Type: Cat. No. 7579 (Helm. Coll. U. S. N. M.); collected
at Isla del Euro, Lake Valencia, Venezuela, July 9, 1918.
Allocreadium chuscoi, new species

Length, .56 mm., width, .29 mm.; body widest behind
middle (Fig. 8). Acetabulum and oral sucker nearly equal in
size; ratio of diameter of oral sucker to that of pharynx about
11 to 4. Diameter of acetabulum, .084mm.

A llocreadium chuscoi.

Genital field, exclusive of vitellaria, occupying the middle
half of the body. Ovary somewhat angular, at the right

34 UNIVERSITY OF WISCONSIN STUDIES

posterior margin of the acetabulum. Uterus short, coiled
somewhat posterior to acetabulum. None of the specimens
examined contained eggs. Genital pore in the median line
immediately anterior to the acetabulum. Cirrus sac elongated,
pear shaped, eleven-fourteenths as long as diameter of acetabu-
lum.

Testes lobate, the anterior one somewhat on the left of the
median line, the posterior one somewhat on the right. Vitel-
laria small, ellipsoidal, arranged in a V-shaped area outside
the intestinal rami and across the posterior end of the body.
Intestinal rami smooth, slender (diam. .02 mm.) extending to
within one-seventh of posterior end of body.

Host: Chusco, Aquidens pulcher Gill, in intestine.

Type: Cat. No. 7562 (Helm. Coll. U. S. N. M.); collected
in mouth of Rio Bue, near Maracayj Lake Valencia, July 19,
1918.

TREMATODE No. 2

Forty trematodes of this species were found in the intestine
of a cula, Curimatus argenteus Eigenmann, caught at the
mouth of the Rio Bue, July 20, 1918. The specimens were

FIG. 9. Trematode No. 2.

not in good enough condition for complete study. Figure 9
shows the general form of the body; the length of which was
.35 ,mm. The suckers are nearly equal in size. The genital
pore is close to the anterior border of the acetabulum.

PMARSE — FISHES OF LAKE VALENCIA, VENEZUELA 35

Clinostomum inter medialis Lament

The adult of this species lives in the esophagus of the
cormorant, Phalacrocorax vigua Viellot. On July 27, 1918,
a bagre (Rhamdia quelen Quoy and Gaimard) collected under
a rock in the Rio Castano contained twelve encysted forms
distributed as follows: 5 in muscles at base of tail, 1 back of
head under skin, 3 under operculum, 3 under membrane cover-
ing floor of mouth. Two other bagres collected at the same
time were not infected with this parasite. The length of the
encysted forms was 6 to 7.5 mm. Similar encysted forms were
also found in an eel (Symbranchus marmoratus Bloch) caught
in the rocks along the shore of Isla del Euro, July 12, and in a
sardina, Astyanax bimaculatus (L.), collected July 20 at the
mouth of the Rio Bue.

Clinostomum Cyst No. 1

A large larval Clinostomum (Fig. 10) was taken from a
cyst in the muscles at the base of the tail of a gaubina, Hoplias
nnilabaricns (Bloch), captured along the shore of Isla del Buro,

FIG. 10. Clinoslomum Cyst No. 1.

July 11, 1918. (Cat. No. 7588; Helm. Coll. U. S. N. M.) It
measures 16 mm. in length. Probably the adult stage is
found in some fish-eating bird.

Diplostomum mataguaroi, new species

Larval forms of this species (Fig. 11) were found in cysts
in the peritoneum, particularly over the swim bladder, and in
the liver of the mataguaro, Crenicichla geayi Pellegrin. The
adult perhaps will be found to belong to the genus Strigea.

Length of entire cyst, 1.54 mm.; length of larva, .92 mm.;
width, .48 mm. The cyst has a thin wall and there is a con-
siderable fluid-filled space between it and the larva.

The body is very flat and clearly divided into two regions
by a constriction a little posterior to the middle. The muscular
oral sucker is followed by a more slender pharyngeal bulb.

36

UNIVERSITY OF WISCONSIN STUDIES

FIG. 11. Diplostomum mataguaroi.

The slender intestinal rami extend nearly to the posterior end
of the body and the middle half of each is more or less sacculate.

The posterior sucker is larger than the anterior and there is
a lobate adhesive organ just behind it.

Type, Cat. No. 7586 (Helm. Coll. U. S. N. M.); collected
from liver of Crenicichla geayi Pellegrin, at Isla del Euro,
Lake Valencia, Venezuela, July 10, 1918.

FIG. 12. Trematode Cyst No. 3.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA

37

TREMATODE CYST No. 3

On July 27, 1918, a mataguaro, Crenicichla geayi Pellegrin,
which had several trematode cysts in its fins and beneath 'its
skin, was caught in the Rio Castano. The cysts -all had the
form shown in Figure 12. The cyst wall was thick but had no
definite outer boundary — the fibers composing- it blending
gradually into the surrounding tissues. There was much more
pigment about the cysts in the fins than about those beneath
the skin. The larva within the cyst measured .28 Jby .16 mm.;
the cyst about .6 by .5 mm. The diameter of the oral sucker
is about one-eighth and the acetabulum somewhat more than
one-fourth the length of the body.

This cyst was not found in mataguaros from Lake Valencia.
It was abundant in two mataguaros caught in the Rio Castano,
July 27. One specimen had the cysts distributed about as
follows: dorsal 60, caudal 30, anal 60, pelvic 90, pectoral 60.
The other had none in the fijis but carried about forty in its
skin.

CESTODA

No adult tapeworms were found in the fishes of Lake
Valencia. The larvae collected probably have their adult
stages in birds or in other fish-eating animals.

FIG. 13. Tapeworm cysts found in Vajencian fishes.

38 UNIVERSITY OF WISCONSIN STUDIES

TAPEWORM CYST No. 4

Two small cysts, .3 mm. long (Fig. 13A) were taken from the
peritoneum of an eel (Symbranchus marmoratus Bloch) 130 mm.
in length, caught in the soft bottom of Lake Valencia with a
mud dredge at a depth of 14.5 m. There are four suckers in
the cyst and the wall is thin.

TAPEWORM CYST No. 5

Groups of small cysts were found in the peritoneum of
sardinas, Astyanax bimaculatus (L.), caught by Isla del Euro,
July 10; also in the same situation in top-minnows, Lebistes
reticulatus (Peters), taken by Isla del Euro July 11 and in
Lake Valencia near Maracay July 24.

The cysts are nearly globular (Fig. 13B) and contain a
larval tapeworm, folded once. They measure .36 mm. jn
diameter.

CYSTS OF UNKNOWN PARASITES

Cyst No. 6

An elongated cyst (Fig. 13C) was found in the peritoneum
of a Chusco, Aquidens pulcher (Gill), caught at the mouth of
the Rio Bue, July 19, 1918. It measures .29 mm. in length.

Cyst No. 7

Globular cysts occurred in the fins of two sardinas, Astyanax
bimaculatus (L.), caught in the mouth of the Rio Bue, July 20,
1919. These dried up on account of a crack in the vial in
which they were preserved. They measured about .42 mm.
in diameter and are perhaps very young cysts of Parspina bagre.

Cyst No. 8

Globular cysts, .1-.17 mm. in diameter, were found in the
peritoneum of chuscos, Aquidens pulcher (Gill), by Isla del
Euro, July 9; and near Maracay in Lake Valencia at a depth
of 16 m., July 26.

' Cyst No. 9

A chusco, Aquidens pulcher (Gill), caught in Lake Valencia,
July 9, at a depth of 16 m., had the liver filled with minute cysts
.017 to .009 mm. in diameter.

ACANTHOCEPHALA

Dr. H. J. Van Cleave has kindly described the acantho^
cephalans, reporting two species.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA

Pandosentis iracundus Van Cleave

39

This minute parasite was found in the chusco, Aquidens
pulcher (Gill), and in the mataguaro, Crenicichla geayi Pellegrin.
Quadrigyrus torquatus Van Cleave

This worm was found in five species of fishes: the guabina,
Hoplias malabaricus (Bloch) ; anguilla, Symbranchus marmoratus
Bloch; mataguaro, Crenicichla geayi Pellegrin; and the sardinas,
Gephyrocharax valenciae Eigenmann and Astyanax bimaculatus
(L.).

NEMATODA

The nematode parasites were sent to Dr. N. A. Cobb of the
Bureau of Plant Industry and as it will probably be some time
before he is ready to report, these worms are listed as "intestinal"
when they occurred in the lumen of the intestine and "visceral"
when they were found encysted among the visceral organs.

CRUSTACEA

Aegathoa lazzari Pearse

Found twice on fishes from Lake Valencia on the sardinas
Astyanax bimaculatus (L.) and Gephyrocharax valenciae Eigen-
mann.

Dolops geayi Bouvier

This argulid was found on fishes, attached to the body at
bases of the fins, and in the branchial and buccal cavities.
The following fishes served as hosts: chusco, Aquidens pulcher
(Gill); mataguaro, Crenicichla geayi Pellegrin; and the guabina,
Hoplias malabaricus (Bloch).

FIG. 14. Porocephalus gracilis.

40 UNIVERSITY OF WISCONSIN STUDIES

ARACHNIDA

Porocephalus gracilis Diesing

This peculiar parasite (Fig. 14) was reported by Diesing
(Shipley, 1898) from Brazil where it occurs in a number of
species of fishes and reptiles. In Lake Valencia it was found
only in the chusco, Aquidens pulcher (Gill), occurring in cysts
in the peritoneum and liver. It was found in chuscos collected
in Lake Valencia at Isla del Euro, July 9, and in others collected
near Maracay, July 22, 26. By the Isla del Buro, July 9, six
chuscos contained cysts as follows : liver : 6, 8, 8, 1 , 5 ; peritoneum :
.7, 1. Near Maracay July 22 and 26 the results from four
specimens were liver: 2; peritoneum: 12, 4, 1.

Beauchamp (1918) has recorded another porocephalid
parasitic in fishes from the Belgian Congo.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 41

BIBLIOGRAPHY FOR FISH PARASITES

BEAUCHAMP, P. DE 1918. Sur quelques parasites provenant
du Congo Beige. Bulletin de la Societe Zoologique de France,
43:14-20.

LAMONT, M. E. 1920. A New Species of Clinostomum. Oc-
casional Papers from the Museum of Zoology, University of
Michigan, No. 83:1-8.

LtiHE, M. Trematodes. Brauer's Siisswasser Fauna Deutsch-
lands. Hft. 17, Abt. 1: 1-217. 1909.

PEARSE, A. S. 1920. Crustacea from Lake Valencia, Venezuela.
Transactions of the United States National Museum.
In press.

SHIPLEY, A. E. 1898. An Attempt to Revise the Family
"Lingualidae" Archives de Parasatologie, 1: 52-80.

VAN CLEAVE, H. J. 1920. Acanthocephala collected by A. S.
Pearse, Lake Valencia, July, 1918. Transactions of the
United States National Museum. In press.

WALLIN, I. E. 1909. A New Species of Allocreadium. Trans-
actions of the American Microscopical Society, 29: 50-66.

WARD, H. B. and WHIPPLE, G. C. 1918. Fresh-water Biology.
N. Y., x+1111.

42

UNIVERSITY OF WISCONSIN STUDIES

LIST OF FISHES WITH REMARKS ON PARASITES

Aquidens pulcher, Chusco

Table VI A shows that this fish carries eight species of
parasites, four of which were not found in other fishes. It also
(Table VI A) has a very large number of parasites per individ-
ual.

TABLE VI*
A. AQUIDENS PULCHER

-

1

1

VO

oo

Os

Locality

D

£

6

0

"B

1 a

4i

^•v

X

^ "S

£

fc

^

rt O

il

ta

•^ to

2

1

II

.1

i

1

w a
> 1

1!

I!

1!

Isla del Buro.

9

6

4-11

0

3-5

0

0

3-. 8

0

6-1.3

Isla del Buro.

10

4

3-55

0

0

0

0

1-2

0

0

Rio Bue

19

4

3-10

1-.3

0

0

0

0

0

0

Maracay. . . .

22

4

2-6

0

0

0

3-2

1-.3

1-.3

3-4

Maracay. . . .

23

1

1-5

0

0

0

0

0

0

0

Maracay ....

26

3

1-.7

0

1-.3

1-50

0

2-2.4

0

1-1.6

Total

22

14-20

i-+

M

-71

3-. 2

7-3

i-+

10-2

* All divisions of this table are arranged on the same plan. Numbers occurring under
columns headed by the name of a parasite refer to number of fishes infected; the second number
being the average for the total catch of fishes.

fThis species is very transparent. It may have occurred before July 9 and been overlooked.
It also kaves its host readily and swims in the water. Such behavior makes statistical records even
more unreliable.

Astyanax bimaculatus , Sardina

This fish (Table VI B) has nine species of parasites, the
largest number of any fish examined in Lake Valencia. Its
number of parasites per individual is not large (Table VII).
It is commonly eaten for food by predacious fishes and other
animals and, as would be expected, carries several immature
parasites.

Astyanax metae, Sardina

Four fishes of this species were caught in the Rio Castano,
July 27. Three carried no parasites; one had fourteen nema-
todes encysted among its viscera.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 43

TABLE VI. B. ASTYANAX BIMACULATUS

E

t-c

0

u

1

1

"S

1

£

'!-

S

*

1

1

Locality

|

B

1

•i

1*

I

I

"rt
C

e

1

«

1

6
fc

2
1

H

la

11

1

IS

"c

1

1

Isla del

Euro. . .

9

1

0

0

0

1-1

1-2

0

1-2

1-2

0

Isla del

Euro. . .

10

9

0

l-.l

0

3-. 4

2-27

3-. 9

7-3

7-6

0

Rio Bue. .

19

2

0

1-1.5

2-2

0

1-.5

0

0

0

0

Rio Bue. .

20

2

0

0

0

1-2.5

0

0

0

1-1

1-.5

Maracay .

22

1

1-1

0

0

0

0

0

0

0

0

Total. .

15

1- 1

2-. 3

?- 3

5-. 7

4-4

3- 6

8-7

9-3

l-.l

Chaestomus pearsei, Coroncho

Ten specimens were caught in the Rio Castano July 16.
Five of these were free from parasites; the other five carried a
total of twenty-seven intestinal nematodes.
Creagrutus beni, Sardina

Ten specimens, caught by the Isla del Euro, July 12, carried
two species of parasites. Nine of the specimens had a total of
108 Parspina bagre cysts in the fins. Two each had a single
intestinal nematode.

Crenicichla geayi, Mataguaro

This fish carried eight species of parasites, (Table VI C)
TABLE VI. C. CRENICICHLA GEAYI

S

1

1
1«

a

Locality

"a
i— %

5

e

!

|

i

I
1

11

u

i

c

1

i

jr

I

1

B

1

!l

II

If

11

1

1

|!

1

Isla del Euro . .

9

6

3-17

5-19

6-3

0

2-4

3-3

0

t-t

Isla del Euro . .

10

4

1-1

3-99

2-6

0

0

2-3

2-3

2-2t

Rio Castano . . .

27

2

0

0

0

2-370

0

0

0

0

Total

12

4-9

8-43

8-3

2-62

2-2

5-1

2- 5

t-t

tThis species is very transparent. It may have occurred before July 9 and been overlooked.
Jt also leaves its host readily and swims in the water. Such behavior makes statistical records
even more unreliable.

44

UNIVERSITY OF WISCONSIN STUDIES

and had the largest number of parasites per individual (Table
VII). The latter is probably due in part to opportunities for
infection through its food, but is also due to the large number
of cysts (Trematode No. 3) present in the fins and skins of two
fishes captured in the Rio Castafio, July 27. These two fishes
were without, any of the seven parasites found in fishes from
the lake and the parasites they carried were not found in any
other locality.

Curimatus argenteus, Cula

This beautiful fish was not often caught and only seven
specimens were examined. Four were without parasites; one
carried a Parspina bagre cyst on its dorsal fin; another had
forty trematodes in its intestine; and the other had a trematode
cyst (No. 2) dorsal to the swim bladder.

Gephyrocharax valenciae, Sardina

Table VI D summarizes the parasites found in this fish.
Although it is commonly eaten by other animals, it does not
contain an unusual number of immature parasites.

TABLE VI. D. GEPHYROCHARAX VALENCIAE

x

8

1

Locality

1

1

1

1

cS

i

3

i

a

9

c

ci

M

1—4

«T

£

1

•§•«

g

05

• •!

ci
P

i

i

1!

5

1

Rio Bue

20

10

0

6-9.8

1-.3

l-.l

0

Maracay. . . .

24

10

l-.l

0

0

0

i-.i

Total

20

1 1

6-5

^ .

1 I

i-+

Hoplias malabaricus, Guabina

This is the largest and fiercest predacious fish in Lake
Valencia. As one would expect it bears a very large number
of parasites per individual and is infected with eight different
species. (Table VI E). Every individual examined was infested
with encysted nematodes.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 45

TABLE VI. E. HOPLIAS MALABARICUS

•

£

f

1

1

c

c

Locality

*3

t— t

c

^tornum

E?

£

1

|

c

1

1

"rt

c

&

0

s

'I

&

<u

^ *"*

a

•8

«G

V

38

"c3 v-

"^

a

0

:I o

oj

s w

O

G*

£

0

>

C/3 W

c/^

(5

Isla del Euro.

9

2

0

0

1-1

0

2-11

2-15

0

1-.5

Isla del Euro.

10

5

0

0

4-2.5

2-. 8

5-23

2-5

0

0

Isla del Euro.

11

3

1-.3

0

2-18

1-.7

3-19

0

0

0

Maracay. . . .

22

2

0

0

0

1-.5

2-41

1-1.5

0

1-1

Maracay. . . .

23

8

0

0

1-.3

l-.l

8-26

0

0

8-6

Maracay ....

28

3

0

2-4

3-12

1-.7

3-40

1-1.7

2-31

2-6

Total

23

j i

2- 3

11-4 3

6- 5

23-29

6-2 7

2-3

12-27

Lebistes reticulatus, Sardina

These little top minnows do not carry many parasites per
individual and are infected by only three species (Table VI F).

TABLE VI. F. LEBISTES RETICULATUS

Locality

Date
July

No.
examined

Trematodes

Clinostomum
cysts

Tapeworm
cyst No. 5

Isla del Euro. .
Maracay

11
24

10

11

l-.l

0

. 2-. 4
1-.5

8-4.1

8-4.4

16-4.2

Total

21

1-+

3^.4

Pimelodella metae, Bagre

Ten of these little catfishes, caught at the mouth of the Rio
Bue, July 29, were not heavily parasitized. Two individuals
had three adult Parspina bagre in their intestines; two others
carried three intestinal nematodes.

Rhamdia quelen, Bagre

Three of these catfishes, caught in the Rio Castano, July 27,
carried three species of parasites among the viscera. One had
twelve Clinostomum intermediates cysts; two each had two
"Cyst No. 8"; one had a nematode cyst.

46

UNIVERSITY OF WISCONSIN STUDIES

Symbranchus marmoratus, Anguila

This eel (Table VI G) had few parasites — two encysted
among the viscera; an acanthocephalan and a nematode in the
intestine.

TABLE VI. G. SYMBRANCHUS MARMORATUS

Date

No.

Clinostomum

Tapeworm

Intestinal

Quadrigyrtts

Locality

July

examined

intermedialis

cyst No. 4

nematodes

torquatus

lamae

Isla del Euro.

9

3

0

0

1-1

1-.3

Isla del Euro.

11

3

0

0

1-.3

1-.7

Isla del Euro.

12

5

1-8

0

0

0

Maracay ....

25

1

0

1-2

0

0

Total

12

1-3.5

l-.l

2-. 4

2-2.5

Phalacrocorax vigua, Cortua (Cormorant)

A single cormorant was examined near Maracay, July 20.
There were fifty-seven trematodes (Clinostomum intermedialis)
in its esophagus, and fifty nematodes in its stomach.

Caiman sclerops, Bava

Four caimans were shot near Maracay and examined for
parasites, July 22, 23. Two were infected with a total of
thirty-four nematodes in the base of the aorta; three had a
total of four nematodes in the wall of the trachea.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 47

GENERAL REMARKS ON PARASITES

Fourteen of the twenty-five parasites found in fishes were
confined to a single host. This may be taken to indicate that
the fish fauna of the lake is rather recent or that the parasites
have a high degree of host specificity, but the knowledge is too
limited to generalize in this connection.

The fishes with the greatest infection by parasites are as
follows:

1. According to total number of fishes infected: Creagrutus
beni, Chaetostomus pearsei, Rhamdia quelen, Hoplias malabaricus,
Crenicichla geayi.

2. According to average number of parasites per individual:
Crenicichla geayi, Hoplias malabaricus, Aquidens pulcher,
Creagrutus beni, Astyanax bimaculatus.

3. According to number of species of parasites: Astyanax
bimaculatus, Aquidens pulcher, Hoplias malabaricus, Crenicichla
geayi, Gephyrocharax valenciae.

Fishes having the fewest parasites were as follows:

1. According to total number of fishes infected: Gephyro-
charax valenciae, Symbranchus marmoratus, Curimatus argenteus,
Pimelodella metae, Aquidens pulcher.

2. According to average number of parasites per individual:
Pimelodella metae, Astyanax metae, Lebistes reticulatus, Gephyro-
charax valenciae, Chaestomus pearsei.

3. According to number of species of parasites: Astyanax
metae, Chaetostomus pearsei, Pimelodella metae, Creagrutus beni,
Rhamdia quelen, Lebistes reticulatus, Curimatus argenteus.

In general the fishes with the most restricted habitat have a
high number of individuals infected, but carry few species of
parasites and have a small average number of parasites per
individual. The most abundant fishes, which have a variety of
food, including other fishes, and a wide range in habitats, gener-
ally have the most parasites in all respects. There are three

48

UNIVERSITY OF WISCONSIN STUDIES

exceptions in one class to the last statement: Gephyrocharax
valenciae, Symbranchus marmoratus, and Aquidens pulcher
all have a large number of parasites per individual and are
infected with a large number of species of parasites, but few
individual fishes are infected.

All things considered the fishes showing the highest parasitic
infection rank in the following order: (1) Aquidens pulcher;
(2) Astyanax bimaculatus and Crencichla geayi; (4) Symbranchus
marmoratus, Curimatus argenteus, Hoplias malabaricus, Gephy-
rocharax valenciae. It will be noted that those toward the
end of the list generally have the diet restricted to fewer items
(Table V) than those at the beginning. This, with the results
presented in the last paragraph, may indicate that a restricted
diet is associated with a smaller percentage of infected fishes. In
other words, the fewer kinds of food a fish eats, the less likely it
is to be infected with parasites.

TABLE VII

Parasitic infection of fishes of Lake Valencia. The figures refer to number
of fishes infected and where there are two, the second is per cent.

Species of fish

•a

c

1>

1

to

a

No. possible
infections

No. fishes
infected

§

<J3

C
$

2
i>

Enteron

Total of average
infections per
individual

Aquidens pulcher . .
Astyanax bimacu-
latus

22
15

8
9

176
135

41(23)
35(26)

K.6)
3(2)

19(11)
19(14)

21(12)
13(9)

32.9 .
11.1

Astyanax metae. . .
Chaestostomus
pearsei
Creagrutus beni . . .
Crenicichla geayi .
Curimatus argen-
teus . . ...

4

10
10
12

7

1

1

2

8

3

4

10
20
96

21

1(25)

5(50)
11(55)
31(32)

3(14)

0

0

9(45)
6(6)

1(5)

1(25)

0
0
15(16)

1(5)

0

5(50)
2(10)
12(13)

1(5)

3.5

5.8
12.2
111.5

6.2

Gephyrocharax val-
enciae
Hoplias malabari-
cus

20
23

5
8

100
184

10(10)

63(34)

7(7)
12(6)

KD
34(19)

2(2)
47(9)

5
42.5

Lebistes reticulatus .
Pimelodella metae.
Rhamdia quelen. . .
Symbranchus mar-
moratus.

21
10

3

12

3
2
3

4

63
20
9

48

20(30)

4(20)
4(47)

6(12)

0

2(10)
0

0

19(29)
0

4(47)

2(4)

1(2)
2(10)
0

4(8)

4.6

.6
9.3

6.5

Total

169

57

886

234(29'

39(6)

115(13)

80(10)

fish.

* Numbers in this column mean number of species of parasites occurring irt each species of

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA

49

Tables VII and VIII show infection of various parts of the
body in relation to habitats. Intestinal parasites appear to
enter most often fishes frequenting the mouths and courses of
rivers. Visceral parasites are most common in fishes from
rivers and muddy lake bottoms.

TABLE VIII

Infection of fishes of all species by habitats. Isla del Euro has rocky pebbly
and sandy shores; the lake shore at Maracay is very muddy and grown up with
rushes and other water plants; the river mouth is like the shore at Maracay;
the Rio Castano has sandy and rocky bottoms. The second number in a
column is per cent. Figures represent actual, not computed, totals for each
habitat.

Locality

No.
exam-
ined

No.

species
para-
sites*

N9.

possible
infec-
tions

No.
infec-
tions

Skin
and
fins

Viscera

Enteron

Isla del Euro.
Maracay. . . .
River mouth.
Rio Castano .

71
46
33
19

31
20
16
6

313

191
97

25

130(45)
66(36)

26(27)
12(48)

16(5)
13(7)
10(10)
0

- 64(22)
38(20)
6(6)

7(28)

50(16)

15(8)
10(10)

5(20) •

Total

169

73

626

234(38)

'39(6)

115(19)

80(12)

*Numbers in this column obtained by adding kinds of parasites occurring for each species
of fish in each locality.

The fins and skin are not often infected in river fishes; in
fact, such parasites are infrequent in other habitats. The
visceral parasites are more common than those in the intestine —
probably because they are usually more or less permanent
residents of a fish, whereas the enteric parasites usually pass out
after a time.

50 UNIVERSITY OF WISCONSIN STUDIES

CONCLUSIONS

Lake Valencia is a large lake which presents typical condi-
tions for the tropics. It becomes stratified during the summer
in relation to temperature and gaseous content. However,
the deep water contains sufficient oxygen for fishes and there is
considerable food present there. Its plankton is not abundant.

The most fishes occur in shallow, littoral habitats. There
are no very large fishes in the lake and the number of fishes
present, as judged by the catch per hour in gill nets, is not as
great as in certain lakes in Wisconsin, which the writer has
investigated by methods like those used in studying this lake.
There is some evidence that the majority of the fishes were
originally inhabitants of rivers. In general the wide ranging
species feed on ubiquitous foods and are able to invade a
number of habitats. The foods eaten by the fishes in Lake
Valencia are, in the order of their importance: mud, immature
insects, plants, molluscs, fishes, adult insects, entomostracans,
oligochaetes, mites, and rotifers. The bottom and the aquatic
vegetation furnish most of the food and plankton is of little
importance.

About twenty-three species of parasites occur in Valencian
fishes. In general the species of fishes which have the greatest
variety of habitats and foods are most infected. River fishes
have fewer parasites than those in the lake.

PEARSE — FISHES OF LAKE VALENCIA, VENEZUELA 51

BIBLIOGRAPHY

EIGENMANN, C. H. 1912. The Freshwater Fishes of British
Guiana, including a Study of the Ecological Grouping of the
Species, and the Relation of the Fauna of the Plateau to that of the
Lowlands. Memoirs of the Carnegie Museum, 5:xx-f-578.

1920. The Fishes of Lake Valencia, Caracas, and the Rio
Tuy at El Concejo. Indiana University Studies, 7:1—6.

JUDAY, C. 1915. Limnological Studies on Some Lakes in
Central America. Transactions Wisconsin Academy of Sciences,
Arts, and Letters, 18:214-350.

1916. Limnological Apparatus. Ibid., 18:566-592.

PEARSE, A. S. 1919. Fishing in Venezuela. Scientific
Monthly, 8:81-88.

1920. Crustacea from Lake Valencia, Venezuela. Trans-
actions of the United States National Museum. In press.

SHELFORD, V. E. 1911. Physiological Animal Geography.
Journal of Morphology, 22:551-618.

PETERSEN, C. G. J. 1918. The Sea Bottom and Its Pro-
duction of Fish-food. Report of the Danish Biological Station,
1-62.

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