1063-0740/01/2702- $25.00 © 2001
Russian Journal of Marine Biology, Vol. 27, No. 2, 2001, pp. 87–93.
Original Russian Text Copyright © 2001 by Biologiya Morya, Saranchova, Flyachinskaya.
L. is an amphiboreal spe-
cies widely distributed in the seas of the Atlantic and
Arctic oceans. It is the most common mollusk species
of the intertidal and upper subtidal zones of the White
Sea and inhabits the same biotopes as its predator, the
L. The distribution range of the
starﬁsh is almost as extensive as that of the mussel: in
the North Atlantic, it is restricted to Iceland and north-
ern Norway, and in the south, to Senegal . Owing to
their eurytopic nature, these species are able to live
under a wide range of temperature and salinity condi-
has a wider range of tolerance to vary-
ing salinities, which enables it to survive in areas where
it co-occurs with starﬁsh. Therefore, it would be of
interest to elucidate the differences in salinity tolerance
in early ontogeny. The present study is a continuation
of a comparative investigation of the tolerance of
to changing salinities [10, 11].
MATERIALS AND METHODS
This work was done at the A.O. Scarlato Biological
Station of the Zoological Institute, Russian Academy of
Sciences (Chupa Inlet, Kandalaksha Bay, White Sea).
were conducted in the
summer and fall of 1985, and with
, in the
summer of 1996 in isothermic rooms at a constant tem-
C) and illumination.
Most gametes, embryos, and larvae at different
stages were obtained in the laboratory. Brachiolarias
and pediveligers were collected directly from plankton.
Artiﬁcial fertilization was carried out as follows.
Unfertilized egg cells were placed in seawater of
reduced or increased salinity (experiment) or of the
normal salinity for the White Sea (25‰, control). One
to two drops of a thick sperm suspension were added
per 250 ml of water. Gametes were taken from several
individuals. To obtain a control larval culture, fertilized
eggs were placed in 5-l continuously aerated aquariums,
and, later on, larvae at deﬁnite developmental stages were
sampled for experiments. The larvae were fed a mixture
of the planktonic algae
sp. Five to ten embryos or larvae were maintained in 10-
to 15-ml vials at different salinities; the water in the vials
was replaced with aerated water at regular intervals.
Survival of the fertilized egg cells and embryos of
the two species was determined by counting the propor-
tion of live and dead egg cells, embryos, and deformed
embryos in a microscopic ﬁeld. For the later develop-
mental stages, the number of embryos and larvae in the
samples was counted. In all cases, the number of live
embryos and larvae is given in percent of embryos and
larvae in the controls. Experiments were performed in
several replicates. Where possible, morphological
changes produced by exposure to high and low salini-
ties were analyzed in detail and compared with devel-
opment in the normal range of salinity. Photographs
were taken using an MFN-14 photo attachment.
The duration of the experiments varied with the
developmental stage. Experiments with starﬁsh embryos
and larvae lasted 2–5 days, and with mussel embryos and
larvae, 7 days because they survive better in culture. For
comparison, we also present original data on the salinity
tolerance of yearling mussels and starﬁshes (see table).
Both starﬁshes and mussels were collected in the sub-
tidal zone, from rafts in mussel farming grounds where
their habitat conditions are fairly uniform.
Egg cell development.
Fertilized egg cells and
dividing embryos were 55–60
m in diameter (Fig. 1a,
The Influence of Salinity on Early Ontogeny of the Mussel
and the Starfish
from the White Sea
O. L. Saranchova and L. P. Flyachinskaya
White Sea Biological Station, Zoological Institute, Russian Academy of Sciences, Saint Petersburg, 199034 Russia
Received January 20, 1999
—The inﬂuence of increased and decreased salinity on early larvae of the mussel
and the starﬁsh
from the White Sea is studied. Fertilized egg cells, embryos, larvae, and year-
lings of the two species were compared. Salinity tolerance changes with the stage of development of mussels
and starﬁsh. Morphological changes occurring in eggs and embryos exposed to extremely high and low salini-
ties are reported.
salinity, tolerance, mussel, starﬁsh, White Sea