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Author: Günther, 1878

Cyclothone microdon Günther, 1878

Diagnosis: body elongate; mouth large; premaxillary teeth even; vomer with teeth. Pseudobranch absent, gillrakers on first arch 20 (19-22), 4-5 on hypobranchial, no rakers in articulation of epi- and ceratobranchial; gill filaments fused basally in broad segrnent shape along hypobranchial; branchiostegal rays 13 (12-14), 5 (6) on epihyal. Dorsal finrays (13) 14; pectoral finrays 9-10; pelvic finrays (5) 6; anal finrays 19 (17-20); dorsal and anal fin origins about opposite; last dorsal and anal finrays not split to base; dorsal adipose fin absent; anus closer to pelvic fin bases than to anal origin. Vertebrae 32 (31-33). Pyloric caecae 3. Scales present. Photophores: SO absent, ORB 1, OP 2, BR 9-10, IV (2) 3 + 10; VAV 5, 3 (4) anterior to genital opening; AC 14-15, one between last anal and first procurrent ray; OA 8 (9); glandular streak between OP weakly developed; supra-caudal gland weakly but distinctly developed reticulum extending less distinctly anteriorly, either side of dorsal base, to dorsal origin; infra-caudal gland similar but confined to procurrent rays. Colour: uniformly dark brown, gular area excepted. Size: male to 49 mm, female to 66 mm SL.

Habitat: oceanic, deep meso- to bathypelagic, precise depth range dependent upon developmental stage, latitude, season: pre-metamorphic postlarvae in upper 50 m; metamorphic post-larvae at 400-800 m; juveniles and adults at 500-2,700 m; no diel vertical migrations. Food: mainly copepods. Reproduction: protandrous, sex reversal at 22-42 mm SL; spawning season summer-autumn; ripe eggs about 0.5 mm diameter; ovulation all or none, with 2,000-10,000 eggs/ovary pair, fecundity increasing in higher latitudes; length at metamorphosis 11-14 mm SL.

Distribution: circumglobal; temperate and subtropical in North Atlantic; abundant in area to about 60° N; northern record 66° 56' N. 14° 41' W.
Replaced in Mediterranean by C. pygmaea.

Eggs, larvae and young stages. Grey, 1964: 185.
Otoliths (sagitta). No data.

Cyclothone microdon