ISSN 1063-0740, Russian Journal of Marine Biology, 2007, Vol. 33, No. 2, pp. 92–97. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © A.V. Tchesunov, D.M. Milyutin, 2007, published in Biologiya Morya.
Nematodes of the genus
occur in samples of marine sediments. The genus was
erected by Cobb , who also described two species,
Until recently the species com-
position of the genus remained unchanged. Single spec-
imens of both the species were occasionally registered
in different regions of the World Ocean, occasionally
rather far from their respective type localities. Andrássy
 emphasized the morphological peculiarity of
and isolated the latter into a separate subfam-
ily, Alaimellinae, within the family Leptolaimidae.
A stimulus for this paper was provided by the regu-
lar occurrence of
in a habitat unusual for this
species, i.e., within the shells of living foraminiferans
in the White Sea, where this nematode
was registered more often than free-living in sediments.
Below we provide a redescription of
description of a new species,
single male example of which has been found free-liv-
ing in bottom sediments.
In two following papers we are going to describe
other nematodes found in the foraminiferans
in the White Sea. In the light of the fact that two
species of this genus, including one species new to sci-
ence, have been found in the Kandalaksha Bay of the
White Sea, we have tried to supplement our knowledge
about the structural peculiarities of the members of this
rare genus and analyze all available information on the
Taking into account new information
on the structure of the esophagus and other organs, we
have revised the diagnosis of the subfamily and pro-
vided an identiﬁcation key for all species belonging to
MATERIAL AND METHODS
Materials for the project (samples of substrate, silty
sand or silt) were collected by scuba divers or using a
trawl in several points close to the White Sea Biological
Station of the Moscow State University (White Sea,
Kandalaksha Bay, Karelian coast).
List of used abbreviations:
a) body length to great-
est diameter ratio; a.d.) body diameter at the area of
m; am.w.) absolute width of amphid,
m; am.w., %) amphid width relative to body diameter
at the level of the amphid, %; b) body length to esoph-
agus region length ratio; c) body length to tail length
ratio; c') body length to anal diameter ratio; c.s.) length
of cephalic setae,
m; diam.ca.) body diameter at the
level of cardium,
m; diam.c.s.) body diameter at the
level of cephalic setae,
m; diam.midb.) body diameter
at the level of the middle of the body,
body diameter at the level of nerve ring,
Free-Living Nematodes of the Genus
(Nematoda: Leptolaimidae): A Description of
from the White Sea and a Revision of the Genus
A. V. Tchesunov
and D. M. Milyutin
Moscow State University, Moscow, 119992 Russia
Russian Federal Research Institute of Fisheries and Oceanography, Moscow, 107140 Russia
Received September 29, 2006
Cobb 1920 and
sp. n. are described and illustrated. Both
the species were ﬁrst recorded for the White Sea in northern Russia.
occurs in the shells of the agglu-
, as well as freely in bottom sediments.
sp. n. is described
from a single male sampled from bottom sediments.
sp. n. is distinguished from two previously
known species of
Cobb 1920 and
Cobb 1920) by having a longer body, longer
cephalic setae, and a wide amphid equal to the respective body diameter. The new species also differs from
by the distinct striation of the cuticular annulations. The
species are additionally charac-
terized by having a posterior glandular widening of the esophagus. An emended diagnosis of the genus
Cobb 1920 and a key for species identiﬁcation are provided.
White Sea, marine nematodes, taxonomy, foraminifera,
, Alaimellinae, Leptolaimidae,