1063-0740/00/2606- $25.00 © 2000
Russian Journal of Marine Biology, Vol. 26, No. 6, 2000, pp. 439–444.
Original Russian Text Copyright © 2000 by Biologiya Morya, Durkina, Garkusha.
The environment has a great effect on oogenesis in
polychaetes. Rapidly reproducing species usually
inhabit unstable environments, while species with a
protracted period of egg development live in relatively
stable environments .
(family Spionidae) is of interest because it is one of a
few specialized polychaetes closely associated with a
single host or a limited number of hosts.
lives in gastropod shells occupied by hermit crabs of
The environments in which this
species occurs are believed to be unstable and unpre-
dictable because of the periodic change of the hermit
crab shell and its migratory activity .
is not capable of gathering food from the substrate
because of the speciﬁc structure of its mouth apparatus,
and it captures food particles only from the water ﬂows
generated by the hermit crab. This increases its depen-
dence on the host. Due to the features of its habitat, the
oogenesis of this commensal polychaete might be
expected to be different from that of free-living poly-
The purpose of the present work is to describe
MATERIALS AND METHODS
The material was collected from May to November
1996 in Vostok Bay (Peter the Great Bay, Sea of Japan).
Polychaetes were obtained by breaking the shells of
various gastropod mollusks occupied by hermit crabs.
If egg masses were found in the polychaete burrows,
the developmental stage of the embryos was deter-
mined using a stereomicroscope.
The polychaetes were ﬁxed with a 10% formalde-
hyde solution, alcohol–acetic acid, Becker’s formula,
and Gendre’s ﬂuid. After ﬁxation, the material was
embedded in parafﬁn. Slices were cut 5
m thick and
stained with hematoxylin–eosin. Proteins in the
gametes were identiﬁed using fast green; RNA was
detected using gallocyanin–chrome alum; glycogen
was detected by PAS reaction; and lipids were detected
with sudan black B. RNA, proteins, and glycogen in the
gametes were quantiﬁed on an FMEL-1 photometric
unit at the following wavelengths: 641 nm for proteins,
550 nm for glycogen, and 572 nm for RNA. The con-
centration of the substances was determined in the
cytoplasm of previtellogenic, early, and late vitello-
genic oocytes and expressed in conventional units; the
total amount of RNA, protein, and glycogen in the cells
was estimated by multiplying the concentration by
cytoplasm volume. Twenty oocytes were measured at
each stage. The quantitative data from cytophotometric
studies were statistically analyzed using a Student’s t-
Polychaete gonads appears as pairs of racemose
forms, and are located in the ventrolateral region of the
body segments (Fig. 1a). In the gonad, there is a wind-
ing genital blood vessel originating at the circular seg-
mentary blood vessel. Gametes closely dispersed
around the blood vessel are in contact with its wall
almost throughout oogenesis (Fig. 1b). Small gametes
(oogonia and previtellogenic oocytes) form a small,
compact cluster at the base of the gonad. As the
gametes develop, the genital blood vessel grows and
Oogenesis in the Polychaete
V. B. Durkina
and A. A. Garkusha
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, ul. Pal’chevskogo 17, Vladivostok, 690041 Russia
Far Eastern State University, Vladivostok, 690600 Russia
Received March 18, 1999
—Oocytes of the polychaete
develop in the gonad, in close contact with the
wall of the genital blood vessel, up to the late stages of vitellogenesis. At the blood vessel wall, between the
neighboring vitellogenic oocytes, and sometimes on the apical surface of the oocytes, there are ﬂattened folli-
cular cells. However, no continuous, well-expressed gonad envelope is found. Oogenesis is asynchronous.
Gametes at all developmental stages, from oogonia to late vitellogenic oocytes, occur in the gonad. Dividing
oogonia vary from 6 to 10
m in diameter. RNA, proteins, glycogen, and lipids accumulate in the oocytes dur-
ing vitellogenesis. The breakdown of the oocyte germ vesicle occurs in the gonad. Before spawning, gametes
accumulate in the coelom and reach 80–90
m in diameter, at which point a new generation appears in the
, intraovarial oogenesis.