New species of the genus Ariosoma, A. dolichopterum (Bathymyrinae), from the waters of Central Vietnam

Abstract

A new species, Ariosoma dolichopterum is described from 30 specimens collected in the coastal waters of Central Vietnam. This species differs from a related species A. anago in lower total number of vertebrae (127–131), lower number of precaudal vertebrae (58–61) and preanal pores (46–50), and larger length of the pectoral fins (39–48% of head length). The distribution of adult and larval forms of this species of congrid eels (Bathymyrinae) in the South China Sea and adjacent waters of western Pacific is given.

Full text

ISSN 00329452, Journal of Ichthyology, 2015, Vol. 55, No. 6, pp. 906–910. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © E.S. Karmovskaya, 2015, published in Voprosy Ikhtiologii, 2015, Vol. 55, No. 6, pp. 719–723.
906
According to the data of several authors, the fol
lowing species of the genus
Ariosoma
are distributed in
the South China Sea:
A. anago
(Temminck and Schle
gel, 1846),
A. major
(Asano, 1958),
A. anagoides
(Bleeker, 1853),
A. megalops
Fowler, 1938 (Smith,
1989, 1999, 2000; Shen, 1998), and, most likely,
A. sazonovi
Karmovskaya, 2004. The latter species is
known from the eastern South China Sea off Philip
pines at the border with the Sibuyan Sea, southwestern
coast of Luzon Island (Karmovskaya, 2004). In the
coastal waters of Central Vietnam, in addition to
A. anago
and
A. megalops
, I found
A. meeki
known off
Japan, as well as
A. dolichopterum
sp. nov, a new spe
cies described earlier (based on adult specimens) as
A. anagoides
(Shen, 1998) from the waters of Tai
wan.According to the number of vertebrae/myomeres,
the latter species of congrid eels (Bathymyrinae) can
be associated with leptocephali described previously as
Ariosoma
sp. 6 (Tabeta and Mochioka, 1988) and
Type II (Mochioka et al., 1991) from the waters off
Taiwan and Okinawa.
This study is devoted to the description of a new
species based on the materials collected from 2005 to
2010 in the coastal waters of Central and South Viet
nam. The fishes were caught with bottom shrimp
trawls on board of local wooden trawlers at the depths
ranging from 10 to 130 m. Measurements and counts
of pores of the seismosensory system were made using
traditional methods applied for congrid eels (Smith,
1989). Numbers of fin rays and vertebrae were counted
on the xrays photographs.
Ariosoma dolichopterum
sp. nova
(Fig. 1)
Ariosoma anagoides
: Shen, 1998, p. 9 (four speci
mens, description, off southwestern Taiwan).
Ariosoma
sp. 6: Tabeta and Mochioka, 1988, p. 49
(brief description, drawing).
Ariosoma
Type II: Mochioka et al., 1991, p. 611.
Figs. 5 and 6 (leptocephali, partim, description and
distribution, waters of Taiwan and Okinawa).
Material. ZMMU 23861, holotype, male
311 mm
TL
, between June 30 and July 1, 2006,
12
°
37
′
N,
109
°
28
′
E, depth 29–44 m, collector
A.M. Prokofiev. Paratypes, eight specimens 104–
320 mm
TL
; ZMMU 23862, two specimens 168 and
193 mm
TL
, June 21, 2005, polygon 4,
12
°
14
′
–12
°
16
′
N,
109
°
17
′
–109
°
19
′
E, depth 22–24 m; ZMMU 23863,
one specimen 320 mm
TL
, collected together with the
holotype; ZMMU 23864, one specimen 291 mm
TL
,
November 24, 2005,
12
°
15
′
N,
109
°
18
′
E, depth 22–
24 m; ZMMU 23865, one specimen 233 mm
TL
, Sep
tember 21, 1984, scientific and commercial vessel
Odis
sei
,
11
°
09
′
N,
110
°
01
′
E, depth 480 m; IO RAS 02824,
one specimen, 132 mm
TL
, June 10, 2006,
12
°
03
′
N,
109
°
13
′
E, depth 11–18 m; IO RAS 02825, one spec
imen 104 mm
TL
, June 17, 2006,
12
°
14
′
N,
109
°
19
′
E,
depth 7–10 m; IO RAS 02826, one specimen 307 mm
TL
, June 26, 2006,
12
°
13
′
N,
109
°
20
′
E, depth 23–
33 m. Nontype specimens: IO RAS 02827, 13 speci
mens 261–365 mm
TL
, 2010,
10
°
47
′
–10
°
38
′
N,
108
°
00
′
–108
°
58
′
E, depth 100–130 m, Phu Quy
Island.
New Species of the Genus
Ariosoma
,
A. dolichopterum
(Bathymyrinae), from the Waters of Central Vietnam
E. S. Karmovskaya
Shirshov Institute of Oceanology, Russian Academy of Sciences,
pr. Nakhimovskii 36, Moscow, 117218 Russia
email: ekarmovs@ocean.ru
Received June 26, 2015
Abstract
—A new species,
Ariosoma dolichopterum
is described from 30 specimens collected in the coastal
waters of Central Vietnam. This species differs from a related species
A. anago
in lower total number of ver
tebrae (127–131), lower number of precaudal vertebrae (58–61) and preanal pores (46–50), and larger length
of the pectoral fins (39–48% of head length). The distribution of adult and larval forms of this species of con
grid eels (Bathymyrinae) in the South China Sea and adjacent waters of western Pacific is given.
DOI:
10.1134/S0032945215060077
Keywords
: congrid eels, Bathymyrinae,
Ariosoma dolichopterum
, new species, Vietnam, South China Sea
BRIEF
COMMUNICATIONS

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Ariosoma, A. dolichopterum
907
Material for comparison.
Ariosoma
sp.,
North West Shelf of Australia: AMS I 26 943001, one
specimen 183 mm
TL
,
20
°
04
′
S,
116
°
10
′
E, depth
64 m; CSIRO, CA 2712, female 266 mm
TL
, the same
data; B 2028, one specimen 149 mm
TL
,
20
°
01
′
S,
115
°
58
′
E, depth 80 m; CA 2714, one specimen
132 mm
TL
, the same data; CA 2721, one specimen
174 mm
TL
, the same data; CA 2339, male 200 mm
TL
,
19
°
52
′
S,
116
°
27
′
E, depth 70 m.
L e p t o c e p h a l i. 37 specimens 35–182 mm
TL
.
Danaexp
, 1929: station 3687 V, one specimen
104 mm
TL
,
08
°
34
′
N,
119
°
36
′
E, Sulu Sea, station
3690 IV, 24 specimens 45–105 mm
TL
,
8
°
02
′
N,
109
°
36
′
E, South China Sea to the southeast of Viet
nam; station 3712 IV, one specimen 150 mm
TL
,
12
°
44
′
N,
110
°
45
′
E, South China Sea, Vietnam; station
3715 I, two specimens 98 and 102 mm
TL
,
18
°
18
′
N,
119
°
36
′
E, South China Sea, Philippines, northwest
ern part of Luzon Island; station 3723 V, three speci
mens 35–78 mm
TL
,
25
°
30
′
N,
125
°
28
′
E, East China
Sea, Okinawa Trough; station 3730 I, one specimen
182 mm
TL
,
16
°
55
′
N,
120
°
02
′
E, South China Sea,
Philippines, Luzon Island; station 3731 II, one speci
men 95 mm
TL
,
14
°
37
′
N,
119
°
52
′
E, South China
Sea, Philippines, Luzon Island; station 3750 IV, three
specimens 70–90 mm
TL
,
4
°
11
′
N,
136
°
36
′
E, Philip
pine Sea, to the south of Palau.
Gal.exp
, station 408,
one specimen 138 mm
TL
,
13
°
44
′
N,
118
°
50
′
E, east
ern South China Sea, Philippines.
(c)
(b)
(a)
Fig. 1.
Ariosoma dolichopterum
sp. nova, holotype ZMMU 23861, 311 mm
TL
: (a) general view; (b, c) head from a side and from
below.

908
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KARMOVSKAYA
D i a g n o s i s. Species of the genus
Ariosoma
with
six supraorbital, eight infraorbital, ten preoperculo
mandibular, and three temporal large pores; with a
welldefined dark medial stripe on the lower surface of
the snout; pectoral fin length 39–48% of head length.
Preanal pores 46–50; total vertebral number 127–131,
precaudal vertebrae 58–61.
D e s c r i p t i o n. Dorsalfin origin slightly before
pectoral fin base, over sixth to eighth pore of lateral
line. Pores in canals of head and lateral line large.
Vert.
129 (127–131), preanal vertebrae 49 (48–50), precau
dal vertebrae 58 (58–61).
D
180–185,
A
120–140,
P
13
(12–14). Rays of dorsal fin to vertical through
anal fin origin 69–79. Pores of lateral line to anal fin
origin 47 (46–50).
SO
6,
IO
8,
POM
10,
ST
3
. Myo
rhabdoi absent.
Teeth not large, about the same size; sharpened on
premaxilloethmoid and in marginal rows of both jaws;
teeth bluntconical on vomer. Anterior end of lower
jaw completely covers premaxilloethmoid at closed
mouth. Premaxilloethmoid comparatively wide, its
length only slightly larger than its width; teeth in five
to seven transverse rows. Posterior end of upper jaw
reaches vertical through middle of orbit. Teeth on jaws
in narrowing bands: in four to seven irregular rows
anteriorly and in one or two rows posteriorly. Vomer
elongated, narrower posteriorly, reaching about one
half of upper jaw length; teeth small, bluntconical, in
five or six irregular rows anteriorly and in two or three
rows posteriorly.
Swimming bladder far behind anal opening. Stom
ach reaches 1/2–2/3 of the distance from gill openings
to the vent.
Leptocephali (nonexterilium type): length 35–
182 mm, total myomere number 127–135, preanal
myomeres 119–124. Last blood vessel at 59 – 66th
myomere.
Some measurements of holotype and
(in the parentheses) six paratypes 104–320 mm
TL
. As
%
TL
: antedorsal distance 15.3 (14.9–17.8), anteanal
distance 45.0 (43.8–46.4), head length 16.7 (16.1–
18.9), body depth at anus 6.6 (5.3–7.6). As %
c
: snout
length 22.6 (20.5–25.2), horizontal eye diameter 18.2
(17.3–23.9), mouth cleft length 29.8 (28.0–33.2),
interorbital width 11.7 (9.3–14.1), pectoral fin length
48.0 (39.4–46.7), branchial opening depth 15.3
(14.2–20.2), interbranchial width 22.1 (14.2–23.6).
Largest specimen 320 mm
TL
, mature female.
C o l o r a t i o n of preserved specimens similar to
that in
A. anago
, but color pattern on dorsal and lateral
surfaces of head more bright and distinct. Head and
back darker than belly; in postorbital area, dark stripes
alternated with more narrow and light stripes. Distal ends
of the rays of dorsal and anal fins black (Figs. 1a and 1b).
At lower surface of snout along axial line, congestion
of melanophores forming a conspicuous dark stripe
(Fig. 1c).
E t y m o l o g y. Latin name “dolichopterum”
means long pectoral fins are typical of this species.
Comparative comments.
A. doli
chopterum
is similar to
A. anago
in the coloration of the
head and body, size, shape, and arrangement of teeth
on the jaws and in the majority of morphometric mea
surements. It differs from
A. anago
in the following
characters: presence of dark stripe on the lower surface
of the snout, smaller number of preanal pores (46–50
vs. 51–55), smaller total number of vertebrae (127–
131 vs. 139–144), smaller number of precaudal verte
brae (58–61 vs. 69–73), longer pectoral fins (39.4–
48.0 vs. 31.0 – 37.2%
с
), and longer swimming bladder
(reached almost the posterior edge of the kidney vs. its
posterior end only slightly behind the anal opening or
before this opening). The new species is similar to the
specimens described by Shen (1998) from the waters
of Taiwan and called
Ariosoma anagoides
in the total
number of vertebrae (127–131 vs. 130–131) and num
ber of rays in the unpaired fins (
D
180–185,
A
120–
140 vs.
D
178–188,
A
132–135) but it differs in slightly
larger number of preanal pores (46–50 vs. 45–46). In
our specimens a ratio between the pectoral fin length
and head length (2.08–2.54) is also similar to that
(2.21–2.60) in the specimens from Taiwan. However,
the pectoral fins are substantially shorter (2.68 – 3.22)
in
A. anago
. In a specimen of
A. anagoides
(BMNH
1867.11.28.299, 312 mm
TL
, Indonesia) that I exam
ined at one time, a ratio between the pectoral fin
length and head length is 3.06, and this ratio in the
specimens called
A. anagoides
and collected off Japan
is 2.83–3.46 (Asano, 1962, p. 77). In 1994, I found six
specimens of unknown species of the genus
Ariosoma
collected in the North West Shelf of Australia (Austra
lian museums, AMS and CSIRO). These specimens
are similar to those described in this study, but, most
likely, they belong to another species. The specimens
from Vietnam are similar to the Australian specimens
in the number of preanal pores (46–50 vs. 49–52),
pectoral fin length and head length ratio (39–48 vs.
36–45%
c
), and in a presence of a dark longitudinal
medial stripe on the lower surface of the snout
(Fig. 1c). However,
A. dolichopterum
differs from the
Australian specimens in a slightly smaller number of
vertebrae (127–131 vs. 133–136) and in significantly
less number of precaudal vertebrae (58–61 vs. 66–68).
The leptocephali with the myomere number (127–
135) similar to vertebral number in adult specimens
A. dolichopterum
were found in the South China, East
China, Sulu and Philippine seas (Fig. 2). Their total
myomere numbers and preanal myomere numbers are
very similar to those in the leptocephali named
Ario
soma
sp. 6 and Type II (127–135 vs. 127–134 and
119–124 vs. 118–128, respectively), which have been
described previously (Tabeta and Mochioka, 1988;
Mochioka et al., 1991) from the waters off Taiwan and
Okinawa. However, they slightly differ in the position
of the last blood vessel (at 59–66th myomere vs. at 64–
72nd myomere). I suggest that a more caudal position

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NEW SPECIES OF THE GENUS
Ariosoma, A. dolichopterum
909
of the posterior blood vessel in the leptocephali of
Ari
osoma
sp. 6 and Type II, most likely, is connected with
a mixed material including some specimens belonged
to another species (
Ariosoma
sp. 7 and Type III) char
acterized by 71–80 myomeres before the vertical
through the last blood vessel. The leptocephali of
Ari
osoma
sp. 6 and
Ariosoma
sp. 7 differ in the total num
ber of myomeres (127–135 vs. 136–151) and in the
number of myomeres to the vertical through the last
blood vessel. However, they show a substantial e xternal
similarity: in both species, the upper part of the last
blood vessel near the notochord is divided into two
short branches (Mochioka et al., 1991. Figs. 5 and 7).
D i s t r i b u t i o n. The new species is distributed in
the West Pacific; and, most likely, it is an endemic spe
cies for the Northern Hemisphere. (In the Southern
Hemisphere in the North West Shelf of Australia, this
species is replaced by another similar not described
species
Ariosoma
sp.). Adult specimens, including sex
ually mature individuals, were collected in the South
China Sea, Nha Trang Bay, at a depth 10–44 m and off
40°
30°
20°
10°
0°
20°
30°
40°
S
160°140°120°100° 130°110° 150° E
10°
N
Fig. 2.
Sites of capture of the studied (
䊉
) adult specimens and (
䊊
) leptocephali of
Ariosoma dolichopterum
sp. nova in the western
Pacific and (
䊏
) adult specimens of
Ariosoma
sp. in the North West Shelf of Australia.

910
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KARMOVSKAYA
Phu Quy Island at a depth 100–130 m, and on the
continental slope at a depth 480 m (one specimen).
Besides, the species was recorded off Taiwan (Shen,
1998) as
A. anagoides
. Leptocephali with myomere
numbers (127–135) similar to those in adult individu
als of the species were collected in the South China
and East China seas between 8° and 25° N (Fig. 2).
The smallest larvae 35–78 and 33–41 mm
TL
, respec
tively, were collected in the East China Sea (our data)
and to the south of Okinawa Island (Mochioka et al.,
1991).
ACKNOWLEDGMENTS
This work was supported by the Russian Founda
tion for Basic Research, project no. 130400328.
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