ISSN 1063-0740, Russian Journal of Marine Biology, 2006, Vol. 32, No. 1, pp. 28–36. © Pleiades Publishing, Inc., 2006.
Original Russian Text © O.A. Golovan’, 2006, published in Biologiya Morya.
Gnathiids are a peculiar group of isopod crusta-
ceans, which are strikingly different from other isopods
in their peculiar morphology, the presence of a meta-
morphosis (including three different stages), a strik-
ingly pronounced sexual dimorphism, and the mode of
life. In the stage of larva, the gnathiids are ectoparasites
of ﬁshes; the adults are free-living organisms, and they
do not feed, but have a degenerated intestine.
In the Sea of Japan, seven species of gnathiids have
been registered belonging to genera
1814 (5 species),
Dollfus, 1901 (one
Monod, 1926 (one spe-
cies). All these species, except
et Honma, 2004, found in the coastal waters of Sado
Richardson, 1910 described
from the southeastern Sea of Japan and then found by
Gur’yanova  in Peter the Great Bay, are known from
the papers of Gur’yanova [1, 2, 4] from the northwest-
ern part of the Sea of Japan. More recent reviews and
identiﬁcation keys for the fauna of Isopoda of Russian
Far Eastern seas have usually dealt only with the free-
living members of the order Isopoda, thus ignoring
entirely the aberrant Gnathiidae.
During the treatment of Isopoda collected in Peter
the Great Bay that were kindly loaned to us by col-
leagues from the Sector of the Benthos of the Paciﬁc
Center of Scientiﬁc Fisheries, we registered one male
and three females of the genus
that were simi-
Gurjanova, 1933, but which dif-
fered from the latter in a series of characteristics. This
allowed us to describe a new species,
In describing the new species, we followed the ter-
minology introduced by Monod  and used later on to
designate unique morphological structures showing no
homologies beyond the limits of the group. In number-
ing the pereonites and pereopods, we followed the
scheme proposed by Cohen and Poore , considering
the ﬁrst thoracic segment, fused with the head and bear-
ing modiﬁed pereopods (pylopods), as pereonite 1; it is
followed by free pereonites 2–6 bearing the respec-
tively designated pereopods.
The type specimens are deposited in the Museum of
the Institute of Marine Biology Far East Division, Rus-
sian Academy of Sciences (Vladivostok).
Order Isopoda Latreille, 1817
Suborder Gnathiidea Hansen, 1916
Family Gnathiidae Leach, 1814
Holotype: a male, 5 mm long, MIMB 12373, Sea of
Japan, Peter the Great Bay, Stn. 126, sample 2,
N, 66 m deep, clayey silt, coll. by
TINRO-Center, June 25, 2003.
Allotype: a female, 4.5 mm long, MIMB 12374, Sea
of Japan, Peter the Great Bay, Stn. 215, sample 2,
N, 120 m deep, silted sand, coll. by
TINRO-Center, June 10, 2003.
Paratypes: females, 2 specimens, 3.7 and 4.2 mm
long, MIMB 12375, sampled together with the allo-
Male, the holotype
(Figs. 1–4). The length of body
(from the tip of mediofrontal process to the posterior
Sp. N., A New Species of Gnathiids
(Isopoda: Gnathiidae) from Peter the Great Bay, Sea of Japan
O. A. Golovan’
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received April 4, 2005
—A new species of isopods of the suborder Gnathiidae,
sp. n. has been described
from Peter the Great Bay, Sea of Japan. The new species is most similar to
Gurjanova, 1933, but
differs from the latter in a series of morphological characteristics of the male: frontal margin of the head bears
a well-pronounced mediofrontal process; each mandible has an unarmed carina and an obscure tooth; pereopod
6 is relatively smooth; the basis, ischium, and merus of pereopod 4 bear strong spurlike processes.
Isopoda, Gnathiidae, new species, Peter the Great Bay, Sea of Japan.