View data on Catalog of Fishes here.
The following description of characters, from Mukhacheva (1980), includes an average value followed by range in parentheses: dorsal-fin rays 14–16; anal-fin rays 14–17; pectoral-fin rays 7–8; branchiostegal rays 12–13; gill rakers on first arch 31– 37, lateral line scales 40–44.
Body relatively shallow. Greatest depth contained 4–5 times in SL (3.2–3.5 times when SL less than 35 mm), depth of caudal peduncle 12–16 times (11–13 times when 8L less than 35 mm). Head length contained 3.5–4.5 times in SL. Interorbital distance wide, contained 8–11 times in head length. Supraorbital crests widely separated, upper parts not contacting above middle of orbit. ventral adipose fin absent.
Photophores. ORB 2; OP 3; SO 1; BR 12 12–13, most often 13; OA 30–32, most often 32; IV 27, all in straight row, apart from 8th displaced upward and laterally; VAV 13–15, most often 14; AC 13–15, most often 14. Row of AC photophores not interrupted; IC 54–57, most often 56.
For a key to photophore terminology, click here.
This species is distinguished from all others of the genus by the following combination of characters: body shallower, moderately elongated; depth 19.7–25.6% of SL. Ventral adipose fin absent; ventroanal distance (V–A) 20. 9–26.0% of SL. Photophores OA 20–32; VAV 13–15; IC 5–1–57.
Temperate and subtropical North Pacific.
The following description from Mukhacheva (1980) applies to all species of Ichthyococcus.
Eye large, telescopic, directed obliquely or dorsally. Interorbital distance less than snout length and eye diameter, thin supraorbital crest above each orbit. Snout short, blunt. Mouth small, straight or slightly oblique; anterior part of lower jaw contained in upper jaw with mouth closed. Teeth on both jaws very small, closely set, of uniform size, in a single row. Vomer lacking teeth, or with few, barely perceptible teeth; palatine, pterygoid and tongue lacking teeth. Gill rakers short, smooth, 19–37 on first arch. Pseudobranchia absent. Body covered with large deciduous scales. Origin of dorsal fin equidistant from end of snout and base of caudal fin or nearer former. Origin of anal fin far beyond vertical through end of dorsal fin. Origin of dorsal adipose fin on vertical through anus. Bases of pelvic fins above middle of dorsal fin. Ventral adipose fin small or absent. Anus immediately in front of anal fin.
Dorsal-fin rays 10–16; Anal-fin rays 12–17; Pectoral-fin rays 7–8; V 6–8; lateral line scales 32–44; vertebrae 38–42 . Photophores. SO 0-1, ORB 2, in front of eyes and beneath center of orbit: OP 3, upper on same level as center of eye or slightly higher, lower anterior approximately on same level as end of maxillary, lower posterior behind it, nearer margin of operculum, BR 11-13. Body with 2 rows of photophores: IV 23-28, 1–7 in straight row, 8th displaced upward and outward, others in straight row, or partly on broken line from 8th to 14th, others in straight row; VAV 9–16; AC 11–15, in unbroken row or with hiatus above last few anal-fin rays. OA 23–34, not reaching anal fin.
Mukhacheva V. 1980. A review of the genus Ichthyococcus Bonaparte (Photichthyidae). Voprosy Ikhtiologii 20(6):771–786.
To at least 130 mm SL
Sagami Sea, Japan [Western North Pacific], 35°09'N, 139°24'E, about 400 meters.
Holotype: ZUMT 55033.
Slim lightfish, also known as Ichthyococcus elongatus, is a species of the genus Ichthyococcus.[1]
Slim lightfish, also known as Ichthyococcus elongatus, is a species of the genus Ichthyococcus.
