Bolshakova et al.: Morphology of larvae of 6 Lampanyctus species in the central South Pacific Ocean 113 
Table 1 
The stations, geographic coordinates, and depth layers at 
which, and the dates on which, larvae of Lampanyctus were 
captured during the 34th voyage of RV Dmitry Mendeleev 
in January—March 1985 in the central South Pacific Ocean. 
Larval specimens caught during this expedition were exam- 
ined for this study. Ichthyoplankton and adult fish were 
collected as part of the expeditions of the RV Dmitry Men- 
deleev along 3 transects between 27°S and 48°S. 
Station 
no. 
Date 
16 January 1985 
17 January 1985 
20-21 January 1985 
22 January 1985 
23 January 1985 
4 February 1985 
5 February 1985 
6 February 1985 
12-13 February 1985 
14 February 1985 
15 February 1985 
16 February 1985 
17 February 1985 
25 February 1985 
27 February 1985 
28 February 1985 
3 March 1985 
Coordinates 
46°50'S, 158°01’W 
45°20'S, 157°33’W 
45°31'S, 157°43’W 
45°53’S, 158°09’W 
41°32’S, 158°05’°W 
38°48’S, 157°54’°W 
37°15’S, 158°03’W 
34°59'S, 158°06’W 
37°56'S, 125°55’W 
39°42’S, 126°01’W 
41°43’S, 125°34°W 
43°06'S, 125°42’W 
44°29'S, 125°42’W 
44°51'S, 134°41’W 
40°47’S, 139°28’W 
37°43’S, 143°00’W 
17°13'S, 156°54’°W 
Depth 
layer 
(m) 
0-200 
0-200 
0-200 
0-200 
0-200 
0-200 
0-200 
0-200 
0-200 
0-200 
0-200 
0-50 
0-350 
0-200 
0-550 
0-500 
0-200 
(Table 1). During January—March 1985, larval and adult 
fish were taken along 3 transects in the central South 
Pacific Ocean between 27°S and 48°S: 1) on 158°W, 2) on 
126°W, and 3) between 135°W and 143°W (Figs. 1 and 2). 
In addition, materials from the collections of the 16th 
expedition of the RV Dmitry Mendeleev to the south- 
western Pacific Ocean in 1976 and of the 29th expedition 
of the RV Akademic Ioffe to the South Atlantic Ocean 
in 2009 were used. The ichthyoplankton was sampled 
during these 3 expeditions by using an Isaacs-Kidd mid- 
water trawl with the Samyshev-Aseev modification. The 
trawl net has a mouth opening of 6 m?, a length of 25 m, 
5-mm mesh without nodes, and cod end liner of 500-ym 
nylon mesh. The specimens were preserved and stored 
in 4% formaldehyde. The larvae were stained with aliz- 
arin following the standard procedure (Taylor and Van 
Dyke, 1985). Data on the adult meristic characters are 
presented in Table 2. 
Information for the following features are included in the 
descriptions: standard body length (SL), head length (HL), 
body depth at pectoral fin base (BD), preanal length (PAL), 
predorsal length (PDL), snout length (SnL), horizontal 
diameter of the eye (ED), number of rays in dorsal fin (D), 
number of rays in anal fin (A), number of rays in pectoral 
fin (P,), number of rays in pelvic fin (P,), number of rays in 
caudal fin (C), number of branchiostegal rays (BrR), num- 
ber of gill rakers (GR) on the upper and lower parts of the 
first gill arch, number of vertebrae (V), 3rd supraanal organ 
(SAO3), and 2nd branchiostegal photophore (Bry). 
Results 
Lampanyctus achirus (Andriashev, 1962) 
Distinguishing features In addition to meristic charac- 
ters, larvae of this species are easy to differentiate from 
those of other lanternfish species by the long, toothy 
rostrum, preopercular spines, pigmentation of the ros- 
trum and postorbital region, and lack of pigment above 
the brain. Preopercular spines have also been found in 
larvae of the black lantern fish (L. niger) and dusky lan- 
ternfish (L. ater) (Moser and Watson, 2001). Character- 
istic differences between larval L. achirus and larvae of 
these 2 species occur in pigmentation. In L. ater, there is 
pigment in the dorsal midline behind the dorsal fin; in 
L. niger, there are melanophores at the base of pectoral 
fins and at the rays of pelvic fins. 
Morphology In our collections, 102 larvae with sizes of 
9.0-22.0 mm SL were found (Fig. 3). The head and jaws 
are large, taking almost half of the body length in the lar- 
vae that were 11.0-16.0 mm SL (HL 46-50% SL), with 
an elongated toothy rostrum (SnL 50-65% HL). The head 
length decreases from about 50% to 38% SL as larvae grow 
from a length of 16.0 mm SL to a length of 21.5 mm SL. 
All the larvae have 3-6 small inner preopercular spines 
and 3 large outer preopercular spines. The length of these 
spines decreases with larval size. The eyes are slightly 
oval and become round to a length of about 15 mm SL (ED 
20-23% HL). The jaws are long and end behind the vertical 
of the posterior margin of the eye. Body depth increases 
with larval size (BD 24-27% SL). The pectoral fins are large 
and fan-shaped. The anus opens far behind the middle of 
the body. The dorsal and anal fins are displaced posteriorly 
(PDL 58-66% SL; PAL 67—75% SL). 
Meristic characters D: 15-17, A: 18-20, P,: 14-16, P,: 8, C: 
6+11—10+6, GR: 6+1+12-14, V: 35-36, BrR: 9. All the rays 
in the fins are distinguishable in the 14.5-mm-SL larva, 
and the definitive number of gill rakers is noticeable to a 
size of 16.0 mm SL. 
Pigmentation Pigmentation of the head includes one 
melanophore at the tip of the lower jaw, a row of melano- 
phores scattered on the dorsal side of the rostrum, and a 
row of 3 large melanophores on the rostrum anterior to the 
eye. The row of 2-5 melanophores (the number of melano- 
phores increases with larval size) at the postorbital and 
opercular regions is located at the level of the middle of 
the eye. Minute melanophores cover the base and rays of 
the pectoral fin. No pigmentation occurs above the brain. 
Pigmentation on the body appears in larvae only up to a 
size of 14-15 mm SL. It includes pigment on the myosepta 
of the oblique myotomes of the abdomen between the pec- 
toral fin and the anus. 
