Bolshakova et al.: Morphology of larvae of 6 Lampanyctus species in the central South Pacific Ocean 121 
we suppose that they may belong to Lampanyctus sp. D. 
Adults of Lampanyctus sp. D have been found in the cen- 
tral South Pacific Ocean approximately between 40°S and 
50°S (McGinnis, 1982), and larvae sampled between 38°S 
and 45°S were found in our collections. 
Distribution Among the Lampanyctus species in the col- 
lections of the 34th expedition of the RV Dmitry Mende- 
leev, this species has the most abundant larvae. A total 
of 110 larvae were collected in the central South Pacific 
Ocean. Larvae of Lampanyctus sp. D were found at 7 sta- 
tions (st. 3010, 3042, 3044, 3049, 3055, 3056, and 3057) in 
a narrow range between 38°S and 42°S in the subtropical 
frontal zone and the northern part of the notal zone in the 
South Pacific Ocean (Fig. 2B). 
Lampanyctus pusillus (Johnson, 1890) 
Distinguishing features Larvae of this species have a deep, 
stout body with a blunt snout. The larvae have character- 
istic pigmentation: the body is almost completely covered 
with melanophores, with a series of melanophores along 
the dorsum, a midlateral series on trunk and tail, and a 
series midventrally below the gut. 
Morphology In our collections, 37 larvae with sizes of 
6.8-13.0 mm SL were found. The morphology of the lar- 
vae examined in our study is significantly similar with 
the morphology that has been described earlier for lar- 
vae from the Atlantic Ocean (Taning, 1918) and from the 
Indian Ocean (Olivar and Beckley, 1997). 
Distribution Larvae of L. pusillus were collected at 5 sta- 
tions (st. 3049, 3050, 3051, 3052, and 3069) between 34°S 
and 38°S in the periphery of the central water mass and 
in the subtropical frontal zone in the South Pacific Ocean 
(Fig. 2C). 
Discussion 
Larvae of at least 11 species of Lampanyctus have been found 
in the southwestern Pacific Ocean. These species are L. achi- 
rus, the winged lanternfish (L. alatus), L. ater, L. australis, 
the festive lanternfish (L. festivus), L. gibbsi, L. intricarius, the 
mermaid lanternfish (L. lepidolychnus), L. macdonaldi, 
L. pusillus, and L. wisneri (Wisner, 1976; Hulley, 1981; 
McGinnis, 1982; Becker, 1983; Zahuranec, 2000). Among 
these listed species, L. macdonaldi is the only species for 
which the early stages of development are unknown. The 
status of the larva that we identified as L. gibbsi or L. wis- 
neri and the larvae of L. lepidolychnus (Olivar and Beckley, 
1997) is not clear. Lampanyctus lepidolychnus is known to 
prefer coastal waters and has not been recorded in the south- 
western Pacific Ocean east of 165°W. (Hulley, 1981; Becker 
and Evseenko, 1986), where all the larvae that we identified 
as L. intricarius were caught. At the same time, the larvae of 
L. lepidolychnus (Olivar and Beckley, 1997) and L. intricar- 
ius (Bolshakova and Evseenko, 2015) are similar. Adults of 
these 2 species differ mainly in the location of photophores, 
and they do not differ in meristic characters. For this reason, 
the species identification for larvae of L. lepidolychnus and 
L. intricarius is still questionable. 
Although larvae of L. lepidolychnus and L. intricarius 
are similar, larvae of the 9 other species of Lampanyctus 
that occur in the southwestern Pacific Ocean differ well in 
pigmentation, body proportions and shape, morphological 
features (e.g., preopercular spines), length and shape of the 
rostrum, and time of metamorphosis. An additional factor 
for the identification of larvae of these species can be the 
region of capture. For example, L. alatus and L. gibbsi do 
not occur in the open waters of the southwestern Pacific 
Ocean south of 30°S (McGinnis, 1982; Zahuranec, 2000). 
The distribution of L. achirus, in contrast, extends as 
far north as 30°S, the latitude that corresponds with the 
southern border of the region of the Subtropical Conver- 
gence (a frontal zone between subantarctic and tropical 
water masses) in the Pacific Ocean. The distributions of 
L. ater, L. australis, L. festivus, L. intricarius, L. lepidolych- 
nus, L. macdonaldi, and L. pusillus are associated with the 
Subtropical Convergence. In general, for the species found 
in the southwestern Pacific Ocean, the distribution of lar- 
vae coincides with the distribution of adults. 
McGinnis (1982) noted the existence of 4 more species 
of Lampanyctus in the South Pacific Ocean: Lampanyc- 
tus sp. A, Lampanyctus sp. B, Lampanyctus sp. C, and 
Lampanyctus sp. D. Lampanyctus sp. A is closely related 
with L. achirus, and they have similar meristic features 
(Table 2). We did not find any significant differences among 
our larval specimens of L. achirus either in larval char- 
acters (i.e., pigmentation, body proportions, and formation 
rates for fin rays) or in the number of gill rakers of the 
first gill arch. Lampanyctus sp. B, in meristic features, is 
most similar to L. festivus and has high counts of pectoral- 
fin, dorsal-fin, and anal-fin rays (P: 17, D: 15, A: 21). Lam- 
panyctus sp. C may be close to L. australis because the 
meristic characters of these species match; in addition, a 
vertical band of pigment posterior to the pectoral fin has 
been noted in juvenile Lampanyctus sp. C. The finding of 
larvae of Lampanyctus sp. D in the examination of our col- 
lections confirms the existence of an undescribed species of 
Lampanyctus in the central South Pacific Ocean. 
Conclusions 
Larval characters, together with the morphology of adults, 
may clarify the intergeneric relationships in the family 
Myctophidae. Comparison of the larval characters of repre- 
sentatives of the genus Lampanyctus sensu lato can confirm 
the possible paraphilia of this group (Denton, 2014; Martin 
et al., 2018). At the moment, the use of the larval char- 
acters in phylogenetic systematics are limited to a small 
number of species of Lampanyctus sensu lato for which 
detailed descriptions of larval stages are available (about 
half of them). We believe that the descriptions presented in 
this article will help clarify the taxonomic status of species 
within the genus Lampanyctus sensu lato. 
