ISSN 1063-0740, Russian Journal of Marine Biology, 2017, Vol. 43, No. 3, pp. 181–189. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © A.S. Maiorova, A.V. Adrianov, 2017, published in Biologiya Morya.
Deep-Sea Sipunculans (Sipuncula) of the Northwestern Pacific
A. S. Maiorova
* and A. V. Adrianov
Zhirmunsky Institute of Marine Biology, National Scientific Center, Far Eastern Branch,
Russian Academy of Sciences, Vladivostok, 690041 Russia
Far Eastern Federal University, Vladivostok, 690950 Russia
Received December 26, 2016
Abstract—Based on the available literature data, museum collections, and our own material, a review is pre-
sented on sipunculan species of the northwestern Pacific that occur at depths greater than 500 m. Brief mor-
phological descriptions showing the main characters used in taxonomy and a key for the identification of
deep-sea sipunculans of the northwestern Pacific to species level are proposed. The key includes 22 valid spe-
cies representing 7 genera and 5 families of Sipuncula.
Keywords: sipunculans, biodiversity, northwestern Pacific
Sipunculans are a well-separated monophyletic
group of marine coelomic worms representing a phy-
lum of the animal kingdom, Sipuncula [13, 29]. The
world’s deep-sea sipunculan fauna has been studied
insufficiently. The most recent revision listed only
22 species of sipunculans from depths greater than 500 m
. This also largely applies to the northwestern
Pacific. Most of the available collections, including
those from the Kuril–Kamchatka Trench area, were
made by trawling during a series of expeditions on the
renowned R/V Vityaz in the 1950s–1960s [3–7]. The
greatest contribution to the description of the museum
material and the inventory of the northwestern Pacific
sipunculan fauna was made by V.V. Murina, who pub-
lished a fairly detailed key to sipunculans of the arctic
and boreal waters of Eurasia . All data on the
world’s sipunculan fauna available at that time were
reviewed by Stephen and Edmonds .
Despite the efforts of researchers, detailed descrip-
tions of live worms are absent because of the poor con-
dition of the bottom-trawl material. Moreover, the
degree of intactness and the quality of the preserved
material do not allow genetic methods to be used for
ascertaining the taxonomic status of some close species,
which is important in the case of the variability of many
morphological characters even within one species.
Many revisions of individual taxa of sipunculans
undertaken in the 1980s have substantially hampered
the use of the previously published taxonomic keys
[14–19, 22]. In 1994, Cutler  published a new
overall review of this group and a new key to sipuncu-
lans of the world, in which he reduced many species,
among them those described by Murina, to synonymy
and the total number of species from 300 to 149.
Unfortunately, this very valuable and important book
lacks illustrations of most species, thus hindering its
use as a field guide. Nevertheless, well-illustrated
papers on the sipunculan fauna of some areas of the
western Pacific appeared later, which substantially
helped the identification of common species of peanut
worms [1, 2, 12, 21, 23, 26–28].
In recent years, interest in the northwestern Pacific
sipunculan fauna has increased in connection with a
series of deep-sea expeditions that have been con-
ducted in this region using the state-of-the-art tech-
nologies for the collection of biological material,
including underwater robotic vehicles [10, 11]. These
investigations showed that even at relatively low spe-
cies richness the sipunculans are an abundant group of
deep-sea benthos in all seas of the Russian Far East,
including abyssal and ultraabyssal depths [25–27].
Up-to-date illustrated guides allowing identification
of this material to the species level have become a
The aim of the present work is to review the data
accumulated to date on the deep-sea sipunculan fauna
of the northwestern Pacific and to provide brief
descriptions and keys for the identification of all spe-
cies recorded in the region at depths greater than 500 m.
By the northwestern Pacific we mean a part of the
Pacific Ocean bounded by the Asiatic coast from the
Bering Strait to 30° N and 180° E.
Analysis of our own and museum material from
deep-water samples showed that 22 valid species of
sipunculans are reliable records from depths below 500 m