Diaphus problematicus

Common Name

Problematic Lanternfish

Year Described

Parr, 1928


Dorsal Fin: 16
Anal Fin: 16-18
Pelvic Fin: 8
Pectoral Fin: 11-12
Gill Rakers: 13-14
Lateral Line: 37-38

Body Photophores
PVO: 2 (first at base of pectoral fin; two PVO in straight line with first PO)
PO: 5 (first well separated from rest; fourth almost directly above third)
VO: 5 (first, fourth, and fifth in straight line along belly; second and third in slightly curved ascending line from first)
SAO: 3 (first two in curved line with fifth VO; third well above second slightly below lateral line)
AOa: 6 (first elevated slightly anterior to vertical from second, second through fifth in line, sixth elevated)
AOp: 4-6 (almost a straight line, first above rear anal fin)
Prc: 4 (curving line with the fourth separated by a larger gap and situated right under lateral line)
PLO: 1 (closer to pectoral fin than lateral line, directly over second PVO)
VLO: 1 (over pelvic fin base but closer to lateral line)
Pol: 1 (right below lateral line; between last AOa and first AOp)

A luminous scale adjacent to PLO is 2-3 times its size.

Head Photophores
Dn: present on the antero-dorsal part of orbit behind nostril; females with Dn small and heart-shaped. Males with enlarged Dn.
Vn: present on the antero-ventral part of the orbit; 2-3 times larger than Dn and triangular in shape in both sexes. Males with enlarged Vn. Dorsal extension of Vn touches Dn on anterior margin of orbit.
Op: 2 (first tiny behind jaw, second above it slightly larger than a body photophore)


Body dark overall, with descaled skin pale. Fins pale. Caudal fin with black speckles. Dark tissue around Dn and Vn.


Maximum size to over 90mm. Mature adults from 68mm.


Continental in distribution, with strays taken offshore with currents. Vertical migrator: found from 375-750m by day and towards the surface by night.

Range Map

 Range Map


Tropical Atlantic from Florida to off the coast of NE Brazil. Also strays in the Gulf Stream and in the central Atlantic.


Hartel, K.E. and J.E. Craddock. 2003. Myctophiformes. pp. 942-951. In: FAO Species Identification Guide to Fishes of the Western Atlantic. (ed. Carpenter, K.), pp. 1308–1369. UN FAO Publishers, Rome.

Nafpaktitis, B.G. 1968. Taxonomy and distribution of the lanternfishes, genera Lobianchia and Diaphus, in the North Atlantic. Dana Report No. 73: 1-131, Pls. 1-2.

Nafpaktitis, B.G. 1977. Family Myctophidae. In: Fishes of the western North Atlantic. Sears Foundation for Marine Research. Part 7, No. 1: 13-258.