Myctophum selenops Tåning 1928

Myctophum selenops

This moderately large myctophid reaches a size of about 72 mm (Nafpaktitis et al., 1977); the largest specimen in the Ocean Acre collections is 65 mm. Myctophum selenops is an uncommon tropical-subtropical species (Backus et al., 1977). It is a “rare” species in the study area, being represented by only 25 specimens. Eighteen specimens were caught during the paired seasonal cruises, 10 of these in discrete-depth samples of which 6 were caught in noncrepuscular tows (Table 23).

DEVELOPMENTAL STAGES.—Postlarvae were 6–11 mm, juveniles 10–34 mm, the only subadult was 58 mm, and the two adults were 59 and 65 mm. Sexual dimorphism was evident in the size and number of luminous scale-like structures in the supracaudal gland, which appears in males at about 30 mm and females at about 35 mm (Nafpaktitis et al., 1977).

REPRODUCTIVE CYCLE AND SEASONAL ABUNDANCE.—The reproductive status and life span of M. selenops in the study area is uncertain. Judging from the numerical dominance of postlarvae (7 specimens) and, particularly, juveniles (15 specimens) and the presence of an adult of each sex in the Ocean Acre collections, M. selenops may be an uncommon breeding resident of the study area.

Apparently spawning takes place in spring or summer. Postlarvae were taken from August to October, and all small (less than 20 mm) juveniles, and both adults (59 and 65 mm) in August to September. The catch from August to October obviously consists of two different year classes and indicates that the species lives at least one year and perhaps longer.

VERTICAL DISTRIBUTION.—Three fish caught in day discrete-depth samples (in winter and late summer) were all taken at 301–350 m. One specimen was caught at night at 100 m in late spring. One fish each was caught at 301–350 m near sunset and at about 200 m near sunrise in late summer.

Myctophum selenops, the Wisner's lanternfish, is a species of lanternfish.