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Fishery Bulletin 118(4) 
Tn 
are present in all specimens and noticeable to a size of 
20.5 mm SL), and one melanophore above the posterior 
part of the anal fin base (approximately at the level of the 
12th pterygiophore). Several melanophores are present 
proximally on the lower caudal fin rays. Internal melano- 
phores are visible above the midbrain and above the otic 
capsules; melanophores are scattered on the dorsolateral 
part of the peritoneum. In the 9.5-mm-SL larva (Fig. 2B), 
melanophores are added at the dorsal fin base and at the 
base of some upper caudal fin rays. An unpaired internal 
melanophore is visible on the anteroventral part of the 
liver on the level of the pectoral fin base; melanophores 
appear above the hindbrain, on the opercle, and on the 
membrane between the branchiostegal rays. Pigmenta- 
tion becomes more intense by a size of 10.7 mm SL (Fig. 
2, C—E) and is added ventrally at some myosepta on each 
side along the anal fin base. Melanophores at the dor- 
sal fin base and above the anal fin base are not located 
symmetrically on each side. This pigmentation pattern 
persists up to a size of 20.5 mm SL (Fig. 2, F and G). Ven- 
trally, almost all individuals larger than 10.7 mm SL have 
a row of 2—4 melanophores: approximately at the level of 
the future PO,, PO;, VO,, and VO;. Pigmentation of the 
caudal fin persists to a size of 20.0 mm SL. 
Photophore formation 
The 8.6-mm-SL larva has Br,, PO,, PO;, and VO, begin- 
ning to form. At a size of 11.0 mm SL, Br, and PO, ; are 
added. Larvae at a size of 13.0 mm SL have Br, 3, Op, », 
PO,_;, PVO,_5, VO,_;, and AOa, 7. At a size of 16.0 mm 
SL, formation of PLO, VLO, SAO, _3, Pol, and AOp,_; ends 
(Fig. 2). By a size of 20.0 mm SL, specimens have a defini- 
tive photophore pattern, but formation of the orbital lumi- 
nous glands is not yet complete: So absent, the dark tissue 
at the future Ant is triangular, roundish Dn connected 
with the dark tissue of the future Vn and Ant, and Vn 
reaches the anteroventral part of the eye (Fig. 3). 
Discussion 
The larvae described herein belong to a moderately deep 
body morphotype (Moser and Ahlstrom, 1972, 1974; Moser 
et al., 1984). They have a few melanophores on the pos- 
tanal ventral midline (Fig. 2) and have no So photophore 
(Fig. 3). In total, 9 species of Diaphus can be found in our 
study area in the southwestern Pacific Ocean: D. ander- 
seni, D. danae, D. effulgens, D. hudsoni, small lantern fish 
(D. meadi), D. mollis, Taaning’s lantern fish (D. termophi- 
lus), D. parri, and D. ostenfeldi (McGinnis, 1982; Bekker 
and Evseenko, 1986). Larvae are known for 2 of these spe- 
cies, D. hudsoni and D. mollis (Olivar, 1987; Olivar and 
Beckley, 1995), and they belong to a different morphotype 
that is moderately slender. In addition, they clearly differ 
from our larvae by the absence of pigmentation at the dor- 
sal fin base and at the branchiostegal rays. Among the 
remaining 7 species, only 3 species, D. effulgens, D. danae, 
and D. ostenfeldi, have no So photophore as we observed in 
Figure 3 
Illustration of the locations of the orbital luminous organs 
in a transformation specimen of Diaphus ostenfeldi that 
has a standard body length of 20.5 mm and was caught 
in the southwestern Pacific Ocean in 1985. Locations of 
the following organs are shown: dorsonasal (Dn), ante- 
orbital (Ant), ventronasal (Vn), branchiostegal (Br), and 
opercular (Op). 
our transformation specimens. One of these species, 
D. effulgens, has fewer gill rakers on the first gill arch than 
we observed in our specimens (17-22 versus 24-25); 
another of those species, D. danae, has more gill rakers on 
the first gill arch (27-30) (Nafpaktitis, 1978; Bekker, 
1983). For these reasons, the Diaphus larvae in the devel- 
opmental series presented herein were identified as lar- 
vae of D. ostenfeldi. 
Comparative notes 
There are several common features in the pigmentation 
between our Diaphus larvae and those described in earlier 
reports (Sparta, 1952; Moser and Ahlstrom, 1974, 1996; 
Pertseva-Ostroumova, 1975; Tsokur, 1975; Olivar, 1987; 
Olivar and Beckley, 1995; Sassa et al., 2003): melano- 
phores behind the cleithrum symphysis, at the peritoneum 
near the terminus of the gut, behind the anal fin base, and 
proximally on the lower caudal fin rays. At the same time, 
larval D. ostenfeldi can be distinguished from all known 
Diaphus larvae by the presence of pigment on the dorsal 
fin base and the branchiostegal rays at lengths 29.5 mm 
SL. One more difference between the larvae of D. ostenfeldi 
and the other Diaphus species is that parietal and perito- 
neal pigmentation appears earlier in development in the 
D. ostenfeldi than in its congeners. In addition, the trans- 
formation of larvae described in this article was still not 
complete even at a length of 20.5 mm SL; our larvae have 
a full complex of photophores typical for adults, but the 
formation of orbital glands was not yet completed. In all 
