Astronesthes karsteni Parin & Borodulina 2002

Astronesthes karsteni is a member of the A. niger species group. The following description, based on Parin and Borodulina’s (2002) revision, applies to all species in the group.

Maximum body depth 4.9–6.7 times in SL. Caudal peduncle depth 1.9–2.6 times in its length. Vertebrae (31–35)+(14–16)= 46–50. Head length 3.3–5.0 times in SL. Eye diameter 3.3–5.5 times in head length. Chin barbel small (0.7–3.5 times in head length), its length decreasing with growth. Terminal bulb usually well developed in juveniles (its shape often species specific), but disappearing in majority of species with growth. Premaxilla with five fangs in main row and two to three small lateral teeth. Comb-like row of teeth on maxilla bearing 11–33 teeth, number increasing with growth. One tooth present on anterior head of each vomer. A row of five to eight teeth on palatines. Gill teeth 14–17 on first gill arch.

Dorsal-fin rays 14–17, A (rarely 12) 13–15, pectoral-fin rays 7–9 (usually eight). Pelvic fin bases situated just in front of vertical at beginning of dorsal fin, sometimes slightly more posteriorly. Beginning of anal fin at level of three posteriormost rays of dorsal fin or posterior to end of its base. Dorsal fin base length 1.7–2.5 times greater than that of anal fin. Dorsal adipose fin originates above 9th to 12th anal–fin ray; ventral adipose fin below 12th to15th photophore of VAV series.

Photophores: BR 17–19(rarely 20), IP 9, PV 12–15, VAV 17–21, AC 10–12, IC 50–55(rarely 56); OV 11–14(rarely 15), VAL 19–22, OA 31–35(rarely 36). Serial photophores of average size, with interphotophore spaces four to six times greater than photophore diameter in adults. Ventral row forming steep curve below base of pectoral fin; three posteriormost photophores of IP series increasingly elevated and three anteriormost photophores of PV series usually steeply descending to level of remaining photophores of ventral row. In AC series. first photophore often elevated compared to others, middle one or two photophores also elevated. Numerous additional photophores present on head and body. In small specimens (SL 30–60 mm), these photophores occur along ventral body margin in regular rows that gradually disappear with growth.

Spots of luminous tissue present on head and body. On upper part of head of small specimens (SL 30–50 mm), spots conspicuous between nostrils, above both orbits, and on nape region. Spots becoming more sparse in adults, transforming into aggregations of separate small "scales" of luminous tissue. There are one to three luminous spots on the skin covering the premaxilla in front of anterior margin of orbit and below anterior part of orbit.

Skin under or covering anterior margin of anterior spot (single or largest one) strongly pigmented; second and third spot, if present, significantly smaller with a more simple morphology. In anterodorsal part of operculum, small spot of luminous tissue present, which is also well distinct in small specimens, but transforming in adults into aggregation of dispersed luminous scales. Luminous spot present on body (large or small), situated posterior to operculum and appearing at a standard length of 40–70 mm. Aggregation of luminous tissue can be found above lateral photophore row below dorsal fin, between lateral and ventral rows below bases of pectoral fin, in front of pelvic fin base.

Postorbital light organ below middle part of orbit or further posteriorly and separated from orbit by dark pigment fold; organ sexually dimorphic, as in other species of the genus. In females, this light organ is small and rounded; in males, significantly larger and oval. Photogenic gland very small, found in middle of light organ in females and in posterior part in males.

Body black, fading to brown or beige in preservative. Fin membranes lightly colored, rays slightly pigmented. Chin barbel (including terminal bulb) with pigment only on anterior part of base; thin and pigmented stem visible inside barbel.

Astronesthes karsteni is a member of the A. niger species group. The following description, based on Parin and Borodulina’s (2002) revision, applies to all species in the group.

Maximum body depth 4.9–6.7 times in SL. Caudal peduncle depth 1.9–2.6 times in its length. Vertebrae (31–35)+(14–16)= 46–50. Head length 3.3–5.0 times in SL. Eye diameter 3.3–5.5 times in head length. Chin barbel small (0.7–3.5 times in head length), its length decreasing with growth. Terminal bulb usually well developed in juveniles (its shape often species specific), but disappearing in majority of species with growth. Premaxilla with five fangs in main row and two to three small lateral teeth. Comb-like row of teeth on maxilla bearing 11–33 teeth, number increasing with growth. One tooth present on anterior head of each vomer. A row of five to eight teeth on palatines. Gill teeth 14–17 on first gill arch.

Dorsal-fin rays 14–17, A (rarely 12) 13–15, pectoral-fin rays 7–9 (usually eight). Pelvic fin bases situated just in front of vertical at beginning of dorsal fin, sometimes slightly more posteriorly. Beginning of anal fin at level of three posteriormost rays of dorsal fin or posterior to end of its base. Dorsal fin base length 1.7–2.5 times greater than that of anal fin. Dorsal adipose fin originates above 9th to 12th anal–fin ray; ventral adipose fin below 12th to15th photophore of VAV series.

Photophores: BR 17–19(rarely 20), IP 9, PV 12–15, VAV 17–21, AC 10–12, IC 50–55(rarely 56); OV 11–14(rarely 15), VAL 19–22, OA 31–35(rarely 36). Serial photophores of average size, with interphotophore spaces four to six times greater than photophore diameter in adults. Ventral row forming steep curve below base of pectoral fin; three posteriormost photophores of IP series increasingly elevated and three anteriormost photophores of PV series usually steeply descending to level of remaining photophores of ventral row. In AC series. first photophore often elevated compared to others, middle one or two photophores also elevated. Numerous additional photophores present on head and body. In small specimens (SL 30–60 mm), these photophores occur along ventral body margin in regular rows that gradually disappear with growth.

Spots of luminous tissue present on head and body. On upper part of head of small specimens (SL 30–50 mm), spots conspicuous between nostrils, above both orbits, and on nape region. Spots becoming more sparse in adults, transforming into aggregations of separate small "scales" of luminous tissue. There are one to three luminous spots on the skin covering the premaxilla in front of anterior margin of orbit and below anterior part of orbit.

Skin under or covering anterior margin of anterior spot (single or largest one) strongly pigmented; second and third spot, if present, significantly smaller with a more simple morphology. In anterodorsal part of operculum, small spot of luminous tissue present, which is also well distinct in small specimens, but transforming in adults into aggregation of dispersed luminous scales. Luminous spot present on body (large or small), situated posterior to operculum and appearing at a standard length of 40–70 mm. Aggregation of luminous tissue can be found above lateral photophore row below dorsal fin, between lateral and ventral rows below bases of pectoral fin, in front of pelvic fin base.

Postorbital light organ below middle part of orbit or further posteriorly and separated from orbit by dark pigment fold; organ sexually dimorphic, as in other species of the genus. In females, this light organ is small and rounded; in males, significantly larger and oval. Photogenic gland very small, found in middle of light organ in females and in posterior part in males.

Body black, fading to brown or beige in preservative. Fin membranes lightly colored, rays slightly pigmented. Chin barbel (including terminal bulb) with pigment only on anterior part of base; thin and pigmented stem visible inside barbel.