1063-0740/01/2701- $25.00 © 2001
Russian Journal of Marine Biology, Vol. 27, No. 1, 2001, pp. 14–20.
Original Russian Text Copyright © 2001 by Biologiya Morya, Kasatkina.
Our studies of collections sampled during the period
from 1880 through 1993 and the available data from the
literature indicate changes in the deep-sea Phragmo-
phora (Chaetognatha) fauna in the region of the western
Bering Sea and northwestern Paciﬁc. Since 1990, the
author has failed to ﬁnd a single specimen of the previ-
ously common species of the genus
extensive examination of plankton samples. The spe-
cies inhabiting the area in the past have been replaced
by others, not described in the world fauna. The global
changes that have occurred in the fauna of vast marine
areas have not gone unnoticed by scientists. It is obvi-
ous that this phenomenon is reﬂected in the signiﬁcant
reorganizations of the system of currents and global
movements of deep-sea water masses. It is interesting
that, in this period, massive morphological abnormali-
ties have been recorded in Chaetognatha . We have
already provided a diagnosis of the genus
elsewhere , and here we would like to present
only the diagnoses of ﬁve new species of this genus,
accompanied by detailed descriptions, drawings, and
differential diagnoses for all known species of this
(Figs. 1a, 2c, 3a–3d)
This species was recorded in plankton
samples collected by Juday, Bogorov-Rass, and oce-
anic type nets during the 24th cruise of the research
in 1993. Altogether, 117
specimens were sampled at depths of 50 to 500 m.
The inventory number is 4-PS; the holo-
type is deposited in the Paciﬁc Institute of Oceanology,
Far East Division of the Russian Academy of Sciences,
Vladivostok. It was isolated from a sample from a hori-
zon of 500–200 m in depth at station 2333 with the fol-
lowing coordinates: 55
E; July 23,
1993, 3480 m deep. The specimen is in the third stage
of maturity and is in the process of spawning (in live
specimens, we have observed the release of mature
eggs while immature eggs were retained).
The adult body is 12–14 mm long. Sac-
like gelatinous structures appear above the level of the
anterior margin of the subenteric ganglion. The portion
of the saclike gelatinous structures located on the tail
region constitutes less than 50% of the total tail length.
There are no lateral ﬁns. The tail ﬁn has regular ﬁn rays.
There are 8–11 grasping spines, the ﬁrst three of which
are serrated. There are 14–16 teeth, arranged in one row
on either side of the head. The apical organ is almost
unnoticeable. Alveolar tissue is located only around the
caudal end and seminal receptacles. The eyes lack pig-
mentation and join both each other and the brain; there
is a nuclear zone. The ciliary loop is elongated and
located primarily on the neck. The caudal end of the
body is tapered and bottle-shaped.
Description of the holotype.
The body is slender,
but does not sag when picked up with forceps, because
the muscular bands are strong. Saclike gelatinous struc-
tures are clearly visible on the lateral ﬁelds. These sacs
look like ﬁns from the dorsal and ventral perspectives.
There are gelatinous medium ﬂippers within the sacs
when the animal is moving, which may produce the
illusion of irregular ﬁssures inside the sacs. The head is
almost 1.5 times wider than it is long. The caudal end
of the body is acute and bottle-shaped, as it is strikingly
tapered from the beginning of the tail ﬁn. Transverse
musculature occupies approximately a third of the
trunk region, being located from the neck up to the pos-
terior margin of the subenteric ganglion.
At stages 2–3 of maturity, the body is 12.9 mm long.
The tail region and subenteric ganglion make up 26.2
and 5.4% of the total body length, respectively. Saclike
On Changes in the Arrowworm (Chaetognatha) Fauna
in the Western Bering Sea and Northwestern Pacific
A. P. Kasatkina
Paciﬁc Institute of Oceanology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received January 11, 1999
—We recorded changes in the deep-sea marine arrowworm (Chaetognatha) fauna in the early 1990s
in the western Bering Sea and northwestern Paciﬁc: the absence of previously common species from the order
Phragmophora and the appearance of representatives of new genera and species of the same order. We present
diagnoses of ﬁve new species of the genus
with detailed descriptions and ﬁgures and also a
differential diagnosis for all known species of this genus, including those described in 1997.
Chaetognatha, fauna, Bering Sea