ISSN 1063-0740, Russian Journal of Marine Biology, 2006, Vol. 32, No. 2, pp. 127–128. © Pleiades Publishing, Inc., 2006.
Original Russian Text © A.V. Rybakov, O.M. Korn, E.A. Ponomarenko, 2006, published in Biologiya Morya.
Rhizocephalan barnacles are a group of marine
invertebrates parasitizing, mostly, decapod crustaceans.
(Lützen et Takahashi, 1997) is a
common species of rhizocephalans, which was known
until now only as a parasite of a widely distributed Jap-
anese coastal crab,
1835). It was ﬁrst described in Japan as
(see ) and then transferred into a new genus
(see ). We have found
along the coasts of Russia (Primorye) and South Korea.
The natural geographical range of its major host, the
, extends from Russian Pri-
morye on the north to Hong Kong on the south, includ-
ing the coasts of Japan, Korea, and southeastern China.
MATERIALS AND METHODS
The specimens of the crab
(Dana, 1851) parasitized by
lected in the coastal area of Vostok Bay, Sea of Japan,
at Vostok Marine Biological Station of the Institute of
Marine Biology, Far East Division, Russian Academy
of Sciences (IMB FEB RAS), in the months June–
August 2004. The animals were collected from depths
of 1.5–2 m using traps. Altogether, 14 specimens of
were collected including 4 females para-
(the percentage of infested crabs
in the sample equaled 28.5%); on one crab we found a
single externa of the parasite, on each of three others—
two externae 15 to 17 mm long (see ﬁgure). All the
externae comprised developing embryos and provided,
under laboratory conditions, 2–3 generations of
RESULTS AND DISCUSSION
The morphological characteristics of the externa of
the parasite, i.e., the shape of the reproductive body, its
external appearance, the position of mantle opening,
smooth external cuticle, and the structure of the stalk,
all agree to the description of the species and demon-
strate that the collected specimens indeed belong to
(see ). This conclusion is also
corroborated by light microscopic data on the larval
development (the number of molts, body shape of the
larvae, development of the furca and frontolateral
horns, pattern of abdomen segmentation, etc.) .
The level of parasitization of
can reach very high values.
In 1998–1999 in Vostok Bay (Peter the Great Bay), the
mean intensity of infestation ranged from 7 to 67%,
sometimes reaching 84% . In Japan, the parasitiza-
tion of the coastal crab with
1.7% in Tomioka Bay and 41.6–79.6% in Inuki Bay
(Kyushu Island) .
is a colonial species
[5, 7]; on a single host several successive generations of
externae develop, each providing no less than three
generations of larvae at intervals of approximately 2
weeks; the fecundity of a single externa is rather high
and equals about 50000 eggs . Thus, the density of
invasive larvae in the coastal zone of the sea could reach
very high values, thus providing a great infestation
level of the potential hosts.
The extremely high infestation level of the crab
in Vostok Bay that
was registered in 1998–1999  could probably be a
reason for the sharp decrease in the population density
of this crab, which we have observed since 2003. In
some coastal areas,
, which was very
common there, has entirely disappeared. On the other
A New Host for the Rhizocephalan Barnacle
A. V. Rybakov, O. M. Korn, and E. A. Ponomarenko
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received November 9, 2005
—In Vostok Bay (Sea of Japan), the parasitic rhizocephalan barnacle
dia: Sacculinidae) was found for the ﬁrst time on a coastal crab
is a common parasite of
, a species very close to
onomic position and biology.
rhizocephalan barnacles, new host,
Polyascus polygenea, Hemigrapsus longitarsis.