MALE ISOPOD REPRODUCTIVE STRUCTURES
Although a groat deal of work has been done on sexual determina-
tion and chromosomes of isopods (see Staiger and Bocquet, 1956, and
Teichmann, 1962 for roviews and full references) little has beon re-
ported on tho morphology of the testes used by most of these studies,
Several authors have included decriptions of specializations of the
male pleopods in their broad surveys of isopods (Richardson, 1905;
Van Name, 1936; Menzies, 1950; Gruner, 1965; Schmolzer, 1965) and
some have included drawings of the pleopods of the Oniscoidea covered
in this paper (Richardson, 1905; Van name, 1936; Hatch, 1947;). Other
aspects of the biology of the eight species studied here have been
reported (Miller, 1936; Ricketts and Calvin, 1939; Menzies, 1950)
but this information did not include drawings or descriptions of the
testes of any species or of the modifications of the male pleopods
in any species of the Flabellifera or Valvifera. This study was car-
ried out to fill in these gaps in our knowledge of these isopods,
ETHODS
The animals studied were collected from intertidal and moist terres-
trial habitats on the Monterey Peninsula. They were either fixed in
ethanol or anesthetized with 15% MgCl. Two or three males of each spe-
cies were dissected from the ventral surface to expose the testes, All
drawings were made with the aid of a camera lucida.
MALE ISOPOD REPRODUCTIVE STRUCTURES
SULT
Figure 1 A-D are of the suborder Oniscoidea and represent four
gonera Alloniscus (4), Armadillium (B), Ligia (C), and Porcellio (D).
The testes may be seen in figure A to extend anteriorly only as far
as the third segment of the pereon while those in figure C extend in-
to the cephalon. Figures B and D show testes of similar form with po-
sitions between these two extremes.
Figure 2 A and B are of the suborder Valvifera and represent two
species of the genus Idothea (Pentidothea). The testes are very sim-
ilar in their form and position and both sets connect to vas deferens
which terminate in the paired penis structure extending posteriorly
from the last segment of the pereon. The uropods of both species have
been pinned open to reveal the pleopods and the tips of the styles on
the second pair of endopodites are visible in I. stenops (B).
Figure 3 A-D are representations of the testes in two genera of
the suborder Flabellifera. In A, the testes of Cirolana harfordi are
seen to lie at the fourth or fifth segment of the pereon and to con-
nect to two vas deferens which extend back under the pleopods to a
region near the anus. The vas deferens can take many different paths.
four more of which are seen in B. In C, the testes of a small Liron-
eca vulgaris are seen to have a similar form to those of C. harfordi
except that they are located at the third or fourth segment of the
pereon and theirvas deferens extend posteriorly to a small paired
penis on the last thoracic segment. The testes of a larger L. vulgar-
is are seen in D to be amorphous masses of tissue as this protandrous
form begins its conversion to a female.
TR
TUR
NALE ISOPOD REPRODUCTIVE:
STRUC
Figure 4 A-D are of the right testes and the left first and sec-
ond endopodites of the four species of Oniscoidea examined above. In
all four species the testes consist of three elongate tubular struc-
tures connected to a sac-like seminal vesicle at uniform intervals
and leading to a vas deferens. The broad, tapering extensions of the
first endopodites are very similar in Alloniscus perconvexus (A), Arm-
adillilium vulgare (B), and Porcellio scaber (D) but is almost absent
from Ligia occidentalis (C). The styles on the second endopodites
are narrow and sickle-like in A. perconvexus (A), A. vulgare (B), and
P. scaber (D), but much broader and more rounded in L. occidentalis (C).
Figure 5 A-E are these same details for the members of the Valvi-
fera and Flabellifera I examined. Both the testes and the endopodites
of Idothea resicata (A) are very similar to those of Idothea stenops.
The widely spaced, narrow, pointed testes of the Valvifera are in
marked contrast to the broad, bulbous testes of the Flabellifera
which all branch from the end of the vas deferens. The testes and
endopodites of Cirolana harfordi (C) are very much like those of a
small Lironeca vulgaris (D) except for the natatory hairs on the ple-
opods of C. harfordi. The larger Lironeca vulgaris (E) has pleopods
with the tapering style on the second endopodite as on the other males
in this suborder (and the female L. vulgaris) but the testes have lost
much of their form and appear to be in a state of transition or degen¬
eration.
A


2


D
id


MALE ISOPOD REPRODUCTIVE STRUCTURES
E

O
A

V

MALE ISOPOD REPRODUCTIVE STRUCTURES

cephalon
—

pereon

-testes
— vas deferens
Lseminal vesicle
paired penis
-scale
(1 cm.)
pleotelson
uropod
-pleopod










style-
A
MALE ISOPOD REPRODUCTIVE STRUCTURES
E







C



D
C

2
A
G
MALE ISOPOD REPRODUCTIVE STRUCTURES
E


D



.


n
B


i


MALE ISOPOD REPRODUCTIVE STRUCTURES
G




D


34
80
28

Mon
L
Ba

Ar

pr
—
MALE ISOFOD REPRODUCTIVE STRUCTURS
DISCUSSION
This study points out that the most variation in male reproduc-
tive structures takes place between suborders and the least between
species of the same genus. The testes are of different shapes and in
different positions in the body cavity, but there are always two sets
of three testes to each male (excepting protandrous forms in transi-
tion) and a vas deferens with variably positioned expansions always
leads from these testes toward the pleotelson. All the species exam-
ined have styles on the second endopodites, presumably to aid in
sperm transport, and some have similar modifications of the first
pair of endopodites. These similarities in reproductive structures
occur where they would be expected if the taxonomy of these isopods
successfully described their phylogeny. Taxonomy in the Isopoda is
usually based on the structure of mouthparts and the shape of body
regions.
The variations observed within suborders probably relate to dif-
ferences in the feeding or reproductive habits of these animals, but
more research is needed to document these relations,
MALF ISOFOD REPRODUCTIVE STRUC!
ACKNOWLEDCE
MSI
I am grateful to Dr. Isabella Abbott for her aid and advice through-
out this project and to Feggy Houk and Bill Johnson for their help
in my literature search.
SUMMARY
Dissections and drawings (with camera lucida) were made of the
testes and endopodites of eight species of California isopods. The
Oniscoidea represented by Alloniscus percorvexus, Armadillidium vul
gare, Ligia occidentalis, and Porcellio scaber have three uniformly
spaced, elongate testes attached to a seminal vesicle at various posi-
tions in the body cavity. All but Ligia occidentalis have a broad
projection from the first endopodite and a sickle-like style from the
second endopodite. The Valvifera are represented by Idothea (Pent-
idotea) resicata and Idothea (Pentidotea) stenops. Both of these spe-
cies have similar elongate testes spread down a thin vas deferens.
There are no special modifications of the first endopodites in either
species and the second endopodites have a long uniformly wide style.
The Flabellifera also show similarities within the suborder. Cirolana
harfordi and small Lironeca vulgaris both have bulbous, sac-like tes-
tes extending from the apex of a narrow vas deferens which may take
many different paths in C. harfordi. The larger L. vulgaris has only
an amorphous mass of tissue for testes as it begins its transforma-
tion to a female. All three forms have similar tapering styles on the
second endopodites.
The patterns of variation of testes structure between suborders
and the similarities between them were noted,
MALE ISOFOD REPRODUCTIVE STRUCTURE

LITGRATURE CITED
Gruner, H. E., 1965. Krebstiere oder Crustacea. V Isopoda 1. Liefer-
ung. Tierwelt Dtsch. 51: vii 149 pp.
Hatch, M. H., 1947. The Chelifera and Isopoda of Washington and Ad-
jacent Regions. Un. of Wash. Publ. in Biol. 10(5): 155-274.
Nenzies, R. J., 1950. The Taxonomy, Ecology, and Distribution of
Northern California Isopods of the Genus Idothea with the De-
scription of a New Species. The Wasmann Journ. of Biol. 8(2):
155-195.
Miller, M. A., 1936. California Isopods of the Cenus Porcellio with
Descriptions of a New Species and a New Subspecies. Un. of Calif,
Publ. in Zool. 41(13): 165-172.
Richardson, H., 1905. Isopods of North America. Bull. U.S. Nat. Mus.
54: 727 pp.
Ricketts, E. F. and J. Calvin, 1939. Between Pacific Tides. Stanford
University Press, Stanford, Calif. 614 pp.
Schmolzer, Karl, 1965, Ordnung Isopoda (Landasseln). Akademie-Verlag,
Berlin. 186 pp.
Staiger, H. and C. Bocquet, 1956. Les Chromosomes de la Super-Espece
Jaera Marina (F.) et de Quelques Autres Janiridae (Isopodes
Asellotes). Bull. Biol. France et Belg. 90: 1-32.
Teichmann, V. H., 1962. Chromosomenstudien an Isopoden unter beson-
derer Beruchsichtigung der Oniscoidea. Mitt Hamburg Zool. Mus.
Inst. 60: 1-22.
Van Fame, W. G., 1936. The American Land and Fresh-Water Isopod Crus-
tacea. Bull. Am. Mus. Nat. Hist. 71: 536 pp.
MALE ISOPOD REPRODUCTIVE STRUCTURS
FICURE CAPTIONS
Figure '. Testes in the suborder Oniscoidea. (A) Alloniscus percon-
vexus (Dana, 1854); (B) Armadillidium vulgare (Latreille, 1804);
(C) Ligia occidontalis (Dana, 1853); (D) Porcellio (Porcellio)
scaber americanus (Arcangeli, 1932). Scale in cm.
Figure 2. Testes in the suborder Valvifera. (A) Idothea (Pentidotea)
resecata (Stimpson, 1957); (B) Idothea (Pentidotea) stenops (Ben-
edict, 1898). Scale in cm.
Figure 3. Testes in the suborder Flabellifera. (A) Cirolana harfordi
(Lockington, 1877). Scale in cm.; (B) variations in the paths of
vas deferensin C. harfordi. Scale in mm.; (C) and (D) small and
large males of protandrous isopod Lironeca vulgaris (Stimpson,
1857). Scales in cm.
Figure 4. Details of testes and first and second endopodites in the
Oniscoidea. (A) Alloniscus perconvexus; (B) Armadillidium vul-
gare; (C) Ligia occidentalis; (D) Porcellio scaber. Scale in mm.
Figure 5. Details of the testes and first and second endopodites in
the Valvifera (AampB) and Flabellifera (C, D, &E). (A) Idothea
resicata; (B) Idothea stenops; (C) Cirolana harfordi; (D) small
Lironeca vulgaris; (E) large Lironeca vulgaris. Scale in mm.