1063-0740/02/2802- $27.00 © 2002
Russian Journal of Marine Biology, Vol. 28, No. 2, 2002, pp. 77–86.
Original Russian Text Copyright © 2002 by Biologiya Morya, Kasatkina.
(Figs. 1a, 1b)
The species was found in plankton sam-
ples collected by a Jeddy net (with a mouth opening of
37 cm) on a cruise of RV “Professor Kaganovskii” in
samples collected in October 1998. More than 60 spec-
imens that were collected from a depth range of 1000 to
500 m deep (adults, at the 3rd and 4th stages) and 100
to 50 m deep (young, juveniles, at the 1st and 2nd
stages) were examined.
The inventory number is RS-12. The
holotype is deposited in the Paciﬁc Institute of Ocean-
ology FEB RAS, Vladivostok. It was found at station 57;
E at 1300 m deep on October 9, 1998
in the depth range of 1000 to 500 m. The specimen is at
the third stage of maturity.
The inventory numbers are PS-12/1–
PS-12/6 and are deposited at the Paciﬁc Institute of
Oceanology, Vladivostok. The paratypes were found at
the same station and in the same sample as the holo-
The body of adult animals is 16 to
18 mm long. Saclike gelatinous structures (SGS)
appear at the level of the anterior end of the subenteric
ganglion. The portion of SGS laying on the tail region
is more than 50% of the length of the latter. The spines
are not serrated and do not have a claw at the distal end.
Vesicular tissue is absent. There is an apical organ, but
it is poorly developed. The eyes lack pigment and the
nuclear zone is present, but there are no marginal cells
around the latter.
Description of the holotype.
The body is slender,
transparent, and weak (sagging if taken by forceps).
The lateral ﬁelds are rather wide; convex elongated
SGS are located on the lateral ﬁelds. A narrow ﬁlm of
lateral ﬁns lacking rays is absent around the SGS. The
gelatinous medium ﬂippers within the sacs may pro-
duce the illusion of irregular ﬁssures inside the sacs
when the animal is moving. The head is wide, is not
fused to the body, and the neck is sharply pronounced.
The caudal end of the body is tapered but not bottle-
shaped. The transverse musculature occupies some-
what less than one-third of the trunk region from the
neck to the level of the anterior end of the subenteric
The body is 17.75 mm long in the specimen at the
third stage of maturity. The length of the tail region and
the subenteric ganglion constitute 27.9 and 6.8% of the
total body length respectively. The SGS appear at the
level of the anterior end of the ventral ﬁn. The narrow
ﬁlm of the lateral ﬁns, which lacks rays, is absent
around the SGS. The length of the SGS constitutes 63%
of the body length. A portion of SGS lying on the tail
region is signiﬁcantly smaller than its trunk region
(4.1 times smaller) and equals about 55.6% of the
length of the tail region, 15.5% of the overall body
length, and 24.6% of the total length of the SGS. The
tail ﬁn constitutes about 5.6% of the body length and
about 20.2% of the length of the tail region, has com-
A New Species of Arrowworms (
Chaetognatha) from the Western Bering Sea
and Northwestern Pacific Ocean
A. P. Kasatkina
Paciﬁc Institute of Oceanology, Far East Division, Russian Academy of Sciences, Vladivostok, 190041 Russia
Received November 23, 2000
—This paper continues a series of publications [1, 2] describing new species of the genus
, which replaced the former meso- and bathypelagic fauna of arrowworms in the southwestern Bering
Sea and northwestern Paciﬁc Ocean in the early 1990s. An expedition aboard RV
repeated plankton sampling across the same area in 1998 using standard transects and stations. The collected
samples again did not contain the species of the order Phragmophora that were very common in that area until
January 1990. The paper presents diagnoses of eight new species of the genus
of the order
Phragmophora, their detailed descriptions, ﬁgures, and differential diagnoses for all species of this genus. This
new information supports the conclusion about global changes in deep-sea and mesopelagic fauna of arrow-
worms (Chaetognatha) in the western Bering Sea.