Author: Günther, 1878
Gonostoma elongatum Günther, 1878
Status in World Register of Marine Species:
Accepted name: Gonostoma elongatum Günther, 1878 (updated 2009-06-25)
Diagnosis: body fairly elongate. Pseudobranch present with 1-3 (5) filaments; gillrakers 19 (18-21), usually 4 on hypobranchial; branchiostegal rays (13) 14. Dorsal finrays 13-14 (12-15), slightly behind midpoint of body, followed by a small adipose fin; pectoral finrays 12 (13); pelvic finrays 8; anal finrays (28) 29-32. Swimbladder regressed (adult). Vertebrae (39) 40-41. Photophores (adult): SO 1, ORB I, OP 3, BR (8) 9, IV 5 + 10, VAV 5 (46), AC 22 (21-23), second and third greatly elevated, second usually higher; forth to sixth lower than seventh, remainder level, OA 13 (14), first two elevated, remainder level, low on body; 17-19 AC over anal fin, (1) 2 between last anal and first procurrent ray; VAV 4 over or slightly anterior to anus, last OA usually posterior to VAV 4; 1-2 supra-caudal and 2 infra-caudal glands; secondary photophores on head and body; white glandular mass just posterior to SO, and similar masses associated with ORB and OA. Colour: dark, flanks thinly silvered, finrays speckled. Size: male to 178 mm, female to 275 mm SL.
Habitat: deep mesopelagic, juveniles and adults at 500-1,200 m, occasionally deeper by day and showing size stratification with depth; diel vertical migration at about 50-400 m by night, juveniles shallowest, but some individuals remain at depth. Food: crustaceans, small fishes. Reproduction: dioecious; males ripe at about 110 mm SL, females at about 200 mm SL; peak spawning period, spring-summer; photophores develop in fishes over 6-22 mm SL.
Distribution: circumglobal, tropical and subtropical; in Clofnam area mostly south of 40° N; northern record, 65° 30' N, 29° 20' W; absent in Mediterranean.
Eggs, larvae and young stages. Grey, 1964: 175.
Otoliths (sagitta). Kotthaus, 1967: 19, fig. 25.