1063-0740/05/3101- © 2005 Pleiades Publishing, Inc.
Russian Journal of Marine Biology, Vol. 31, No. 1, 2005, pp. 28–35.
Original Russian Text Copyright © 2005 by Biologiya Morya, Zhadan.
Pectinids, one of the most active bivalve groups, are
capable of avoiding predators using jet propulsion.
Their active behavior is essentially the result of highly
developed sensory systems. Their visual system
includes numerous eyes situated at the mantle periph-
ery. The tactile system features numerous large, mid-
dle-, and small-sized tentacles of the mantle edge. The
chemical sense is provided by the osphradium, and the
sense of balance is produced by statocysts, which are
situated in the cerebral ganglion. In addition, pectinids
have a peculiar organ of hearing, the abdominal sense
organ (ASO), which is highly sensitive to water-borne
vibrations [5, 24]. The presence of such a specialized
organ draws a distinction between bivalves and the
The ASO was ﬁrst described by German researchers
at the end of the nineteenth century (Eisig, 1887, cited
in [16, 20, 21]). Later on, it was studied by light [11, 22]
and electron microscopy [3, 4, 6, 7, 13, 16]. The ASO
is the biggest of the known mechanosensory organs. In
some species, it is up to 5 mm long and 2 mm thick. Its
sensory epithelium includes some 4 million receptor
cells, some 90% of its overall cell number. These cells
have a single long (>200
To date, the ASO has been found in members of
19 bivalve families of the subclasses Pteriomorpha and
Palaeoheterodonta . The ASO is a paired organ.
However, in mollusks resting on the lateral side, such as
Pectinidae and Ostreidae, only the right ASO is present.
Interestingly, bivalve mollusks lacking the ASO
possess organs structurally similar to it. Thus, in Tellin-
idae, this is the cruciform sense organ; in Nuculidae,
Stemphell’s organ. Some authors believe these organs
also serve to perceive water-borne vibrations [10, 14,
18]. Thus, bivalves, as opposed to gastropods and ceph-
alopods, evolved specialized mechanosensory organs,
functionally analogous to the acoustico-lateral system
of the vertebrates.
It is known that in higher vertebrates, acoustico-lat-
eral receptors are involved in the acoustic system of
con- and interspeciﬁc communication, also including
effector systems of acoustic signal production. Bivalves
seem to lack the effector system. Their mechanosen-
sory systems are only capable of detecting mechanical
water-borne vibrations. This study pursues the goal to
elucidate the possibility of such detection in two pec-
tinid species and the role of the ASO in this process.
MATERIALS AND METHODS
Adult Japanese (shell height of 12–15 cm) and Swift
scallops (shell height of 6–10 cm) were collected in
Peter the Great Bay from June to August. Immediately
after collection, the mollusks were divided into three
groups, each of 5 animals. The ﬁrst group was left intact
(control 1). In mollusks of the second group, a portion
of the mantle fold below the ASO was removed (control 2).
In animals of the third group, the ASO was removed.
After the operation, the mollusks were kept in the sea in
Directional Sensitivity of the Japanese Scallop
and Swift Scallop Chlamys Swifti
to Water-Borne Vibrations
P. M. Zhadan
Paciﬁc Oceanological Institute, Far East Division, Russian Academy of Sciences,
Vladivostok, 690041 Russia
Received January 29, 2004
—Behavioral experiments were conducted on two bivalve species—the Japanese scallop
and the Swift scallop
—to elucidate the role of their abdominal sense organ
(ASO) in directional sensitivity to water-borne vibrations. The thresholds were determined at 140 Hz. Both spe-
cies displayed the highest sensitivity to vibrations, the source of which was placed above the animal (opposite
to the left valve), rostro-dorsally to its vertical axis. Removal of the ASO led to loss of directional sensitivity
and a considerable increase in the sound reaction threshold. Both species were sensitive to modulated ultrasonic
vibrations in the range of 30–1000 Hz. This is proposed to be caused by modulated ultrasound effects, provok-
ing weak oscillations of the shell valves at a modulation frequency.
behavior, mollusks, directional sensitivity, mechanoreception, abdominal sense organ.