ISSN 10630740, Russian Journal of Marine Biology, 2010, Vol. 36, No. 5, pp. 331–339. © Pleiades Publishing, Ltd., 2010.
Published in Russian in Biologiya Morya.
Studies on the Hydrozoan fauna of the northwest
ern Pacific are of obvious interest, as the most impor
tant monograph containing data on the hydroids and
hydromedusas of FarEastern seas of Russia was pub
lished more than 50 years ago . According to its
author, all seas of this region are dominated by boreal
species; however, some members of arctic and sub
tropical faunas could also be encountered . The
level of knowledge concerning both certain water areas
of the region and different taxonomic groups is also
different. This primarily regards studies dealing with
hydromedusas (Cnidaria: Hydrozoa) of the north
western Sea of Japan. For most species there is no
information about their distribution, density, schedule
of planktonic life, or peculiarities of morphology and
variability. In many publications on zooplankton the
authors present no species lists of hydromedusas and
mention only the most common planktonic organisms
[5, 15]. Since the time of publication of Naumov’s
monograph , several more species of hydromedusas
have been revealed in the northwestern Sea of Japan
and the taxonomy of the group has somewhat
changed, as certain species appeared to be invalid.
Thus, it has become necessary to specify and supple
ment the existing species list of the fauna of hydroid
medusas in the northwestern Sea of Japan; these were
the goals of our study.
MATERIALS AND METHODS
Hydroid medusas were collected in 2002 and 2007
in Vostok and Pos’eta (Troitsa Bay) bays; in 2008
around Russky Island (Peter the Great Bay, Sea of
The article was translated by the authors.
Japan) and in 2007 in Kievka Bay (see figure and
table). In Vostok Bay the samples were collected from
late April through September, approximately once
every 2 weeks; In Kievka and Troitsa bays they were
collected only once. Altogether, 144 planktonic sam
ples were collected using Juday nets (vertical sam
pling) with a filtering cone made of no. 59 mesh. In
Vostok Bay we used a net with mouth diameter of
35.7 cm; at other stations, a net 30.6 cm in diameter
was used. The samples of hydroid medusas are depos
ited in the Institute of Marine Biology FEB RAS.
The system of orders of Hydrozoa is provided fol
lowing the paper by Arai and BrinkmannVoss .
RESULTS AND DISCUSSION
In the early 20th century, in the “Fauna Rossii”
series (Fauna of Russia) monographs by Linko (1911,
1912) and Kudelin (1914) were published dealing with
hydromedusas and based on the fundamental collec
tions of the Zoological Institute of the Russian Acad
emy of Sciences (cited after ). These presented
data for the first time on the species composition of
hydroids in different water areas, including the north
western Sea of Japan; however, no information about
hydromedusas inhabiting this region was provided.
The list of hydroid medusas in the environs of
Vladivostok compiled by Yamada  comprises
13 species; among the latter only
a medusa stage in its life cycle.
According to Naumov , the Sea of Japan is
inhabited by 99 species of hydroids. Among the latter,
15 species have a freeswimming medusa stage in the
Fauna of Hydromedusae (Cnidaria: Hydrozoa)
of the Northwestern Sea of Japan
T. N. Dautova
and E. A. Petrova
Institute of Marine Biology, Far East Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
Academy of Ecology, Marine Biology and Biotechnology, Vladivostok, 690010 Russia
email: firstname.lastname@example.org, email@example.com
Received November 19, 2009
—A brief overview of studies of hydromedusae (Cnidaria: Hydrozoa) of the northwestern Sea of
Japan is provided. Based on literature data and plankton sampling by the authors, an annotated checklist of
hydromedusae of the northwestern Sea of Japan was compiled for the first time. It includes 25 species belong
ing to 20 families and 5 orders.
hydromedusae, Hydrozoa, Cnidaria, fauna, Sea of Japan.