ISSN 1063-0740, Russian Journal of Marine Biology, 2006, Vol. 32, No. 6, pp. 353–359. © Pleiades Publishing, Inc., 2006.
Original Russian Text © A.P. Kasatkina, 2006, published in Biologiya Morya.
New species of arrowworms have been discovered
in the northwestern Sea of Japan (coordinates:
E; depth, 3600 m); at a horizon of
80–0 m, on November 30, 2000; at 8.30 a.m. In that
area and exactly at that time, an eddy was registered.
Such eddies transferring surface waters from the coasts
of Japan to Russian coasts have been also registered
previously [6, 8]. It is not improbable that these species
of arrowworms inhabit the Japanese coasts and were
transferred into the western part of the sea with trans-
versal eddy ﬂows. Below, we present a diagnosis of a
and four new species and an
identiﬁcation key for genera of the family Sagittidae.
Type materials are deposited in collections of the
Paciﬁc Oceanological Institute, Far East Division, Rus-
sian Academy of Sciences, Vladivostok.
Body is nonrigid, sagging if taken with forceps. Lat-
eral ﬁns are absent; instead of lateral ﬁns, there are con-
vex saclike gelatinous structures (SGS). Intestinal
diverticula on midgut are absent. Trunk gut is not vacu-
olated. Ciliary loop appears in front of eyes, at the level
of brain; its trunk part is not longer than the head part.
Part of posterior pair of SGS located on trunk region is
larger than the part located on head region. Rays are
present only in tail ﬁn, where also rayless zones can be
present. Vesicular tissue consists of large cells, some-
times fused to each other, as is the case in the species of
Central nuclear area of eye is
pigmented and clearly separated from peripheral zone.
The new genus differs from
other genera of the family Sagittidae in the absence of
lateral ﬁns on the trunk; instead of lateral ﬁns, there are
convex saclike gelatinous structures.
“ab” means “to be different” (Latin).
FAMILY SAGITTIDAE Claus et Grobben, 1905
On the ventral side of head, around mouth, there
are two pairs of dental rows. The family comprises 18
IDENTIFICATION KEY FOR GENERA
OF THE FAMILY SAGITTIDAE
1 (34). Lateral ﬁns are present
2 (3). Only 1st pair of lateral ﬁns is present; 2nd pair
representsﬂattened SGS 1.
3 (2). Two pairs of lateral ﬁns are present
4 (30). Eyes are present
5 (31). Eyes have a central nuclear area and dark
6 (19). Ciliary loop is located at the level of eyes or
in front of eyes
7 (18). Spines are not serrated
8 (11). Part of 2nd pair of ﬁns located on tail region
is larger than the part located on trunk region
9 (10). Intestinal diverticula on trunk gut are present
10 (9). Intestinal diverticula on trunk gut are absent
11 (8). Part of 2nd pair of ﬁns located on tail region
is smaller than the part located on trunk region
12 (13). Intestinal diverticula on trunk gut are
13 (12). Intestinal diverticula on trunk gut are absent
14 (15). Trunk part of ciliary loop is larger than its
head part 5.
Quoy et Gaimard, 1827
Finding of New Species of Finless Sagittids
(Sagittidae: Chaetognatha) in the Northwestern Sea of Japan
A. P. Kasatkina
Paciﬁc Oceanological Institute, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received May 3, 2006
—Diagnosis of a new genus
gen. n. and detailed descriptions and drawings of four new
species, as well as keys for the identiﬁcation of genera of Sagittidae, are given. The new species differ from
species of other genera of Sagittidae by lacking lateral ﬁns on the trunk. Instead of two pairs of lateral ﬁns, these
species have saclike gelatinous structures. These structures were previously found only in the species of Euk-
rohniidae (see [2, 4]). The presence of saclike gelatinous structures instead of ﬁns is probably a plesiomorphic
feature, which is retained only in some species.
Keywords: Chaetognatha, new genus