1063-0740/03/2904- $25.00 © 2003
Russian Journal of Marine Biology, Vol. 29, No. 4, 2003, pp. 230–235.
Original Russian Text Copyright © 2003 by Biologiya Morya, Selin, Vekhova.
The availability of a reliable mechanism of bottom
attachment is an important condition for normal ability
to live in bivalves that are speciﬁed by an attached
mode of life on a substrate surface. In representatives of
fam. Mytilidae the given function is carried out by the
so-called byssus complex, the general pattern of which
is rather similar in various species [4, 5, 18]. The retrac-
tor muscles of the foot and of the byssus, the develop-
ment of which may serve as evidence for tenseness of
the environment conditions and for a degree of accli-
mation of the organism to its environment, also take
part in the attachment of the mollusk to the ground.
However, this approach has not received due attention
in research into the morphology and ecology of bivalve
mollusks, where prime attention has been given to anal-
ysis of adaptive traits of the shape of their shell [20, 23].
In this connection we have tried to analyze the mor-
phological adaptations of Gray’s mussel
(Dunker, 1853), a typical representative of
upper sublittoral communities of the Sea of Japan, the
South Kuriles, and Hokkaido Island , by investigat-
ing the effect of environmental conditions on the fast-
ness of attachment to the ground, on body height, and
on the shape of the shell. The potential fastness of
attachment of a mussel was judged from imprints of the
retractor muscles on the inner surface of the shell, the
structure successfully used to solve problems of sys-
tematics and phylogeny of bivalves [14, 16, 17].
MATERIAL AND METHODS
Gray’s mussel was sampled from its three typical
habitats in Vostok Bay (Peter the Great Bay, the Sea of
Japan) using SCUBA gear. Station 1 is a rocky site with
a clumpy pile at the open coast subjected to frequent
surf; the mollusks were taken from the depth 1 m there.
Station 2 is also rocks of the cape subjected to surf
action; animals were selected from depths of 10–22 m.
Station 3 represents an example of Gray’s mussel set-
tlements on soft bottoms in the innermost part of bays
of South Primorye, where joint aggregations of Gray’s
mussel and of
are widespread in
areas free of wave action at depths of 2–10 m. [1, 13, 15].
To study the effect of the environment on the shape
of the shell, about 200 individuals of
various sizes (ages) without signs of bending of valves
at the senile stage  were taken at random from each
biotope. Respective to the modern notion on the posi-
tion of the fore, back, dorsal, etc., parts of the body of
Mytilidae , the length (L), height (H), and width
(D) of the shell were measured to 0.1 mm with calipers
in all mussels. The live body mass was measured to 1 g.
Epibionts from the mollusk surface and particles of
ground from the net of byssus threads were removed
prior to measurements. Muscle scars of the anterior (S
and posterior (S
) retractor muscles of the foot (fur-
ther—scar) after removal of byssus and soft body of
mollusk (Fig. 1) were estimated at the dextral valve of
the shell in 50–55 individuals of
. For that
purpose the greatest and least diameters of scars were
measured under a stereomicroscope, then those data
were used for calculation of the area of the ellipse. The
scar area of the posterior retractor was estimated by
Geron’s formula for triangle projection, measuring by
compasses sides of the homonymous imaginary ﬁgure.
The age of mussels (T) was estimated by growth rings
on the shell surface and by structural marks on the longi-
tudinal cut of the valve . The dependence between the
Morphological Adaptations of the Mussel
(Bivalvia) to Attached Life
N. I. Selin and E. E. Vekhova
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received February 5, 2003
—The morphology of the mussel
from different biotopes manifesting the
adaptation of this mollusk to attached life on the bottom surface was studied. It was established that coloniza-
tion of rocky coastal areas with active hydrodynamics by mussels is related to retardation of linear growth rates,
the formation of convex shells, and vigorous development of retractor muscles of the foot and byssus. An envi-
ronment protected from the effect of surfs on silted bottoms facilitated the fast growth of mussels, which
resulted in the formation of an elegant ﬂat shell. In that biotope mussels are speciﬁed by a rather poor develop-
ment of the muscles responsible for its attachment to the substrate.
morphology, body height, acclimations, mussel