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Serial photophores in lateral row (OA) 32–35, of which 19–22 behind pelvic fin insertion (VAL); 51–55 photophores in ventral row to tail (IC); ventral row forming a pronounced U-shaped bend between pectoral fin bases. Barbel about half as long as head, slender, usually without modified tip, but with a short terminal swelling in some large specimens. Dorsal-fin rays 18–21. Color of head and body black; in larger specimens pale patches on head above nostril and covering most of gill cover, sometimes others.
A member of the "cyaneus" group with a pronounced U-shaped bend in the IV at the level of the pectoral fin . Serial photophores small, interspaces in OV more than 4 times photophore diameter. Barbel about half as long as head, not sexually dimorphic, end bluntly rounded, terminal 10% of length sometimes slightly swollen in large specimens. 47-49 (32-34 + 14-16) vertebrae. More than 40 pairs of gill filaments on the ceratobranchial of the first arch. Vomerine teeth weakly developed, often lacking. Second premaxillary tooth about twice as long as first in adults and much longer than others. Color black.
Oceanic, but not far from island or continental slopes. Atlantic only, between 32° N and 30° S.
Mesopelagic.
Gibbs RH, Jr. 1984. Astronesthidae. In: Whitehead PJP, Bauchot M-L, Hureau J-C, Nielsen J, Tortonese E, editors. Fishes of the North-eastern Atlantic and the Mediterranean. Paris: UNESCO. p 325–335.
Astronesthes macropogon is a member of the Astronesthes cyaneus group. The following is a descriptive diagnosis for the Astronesthes cyaneus group from Goodyear and Gibbs (1970). The diagnosis and descriptions that accompany this page are limited to distinguishing characters within the group.
This species group has the highest dorsal-ray count in the genus, 16–21, with 16 occurring uncommonly in only one species and 17 uncommonly in the other three species (Table 1). No others species of Astronesthes is known to have more than 17 dorsal rays. Adults, and often juveniles, have a prominent patch of luminescent tissue on the operculum. Such an extensive opercular patch is found otherwise only in some populations of Astronesthes indicus. The photophores on the AC row are continuous, without the elevated middle photophores that characterize the "chrysophekadion" group of species. The barbel is simple, either without a terminal swelling or with a poorly developed one. The total number of serial photophores is low (IC 47–56, OC 37–46) in the "cyaneus" group and all four species lack parietal bones in the cranium.
When the opercular luminous patch is developed, species of the "cyaneus" group may confused only with A. indicus which can be distinguished on the basis of a very low photophore count (IC 28 or less). When the opercular patch is not developed, a dorsal-ray count of 18 or more is diagnostic. Small or damaged specimens without an opercular patch and with a dorsal-ray count of 16 (found in A. lamellosus) or 17 (the mode in lamellosus, uncommon in the other three species) may be identified by barbel shape or photophore counts.
Among those species of Astronesthes that may have 16 or more dorsal rays, A. cyclophotus (Atlantic), A . neopogon (Atlantic), A. gemmifer (Atlantic and Indo-Pacific), and A. luetkeni (Indo-Pacific) have the terminal end of the barbel modified to form a structure more complicated than a simple swelling. All other confusing species have either a simple barbel or a slight terminal swelling, as does the "cyaneus" group. The Atlantic species, A. leucopogon has fewer serial photophores than the "cyaneus" group (VAV 15 or fewer vs. 16 or more; IA 35 or fewer vs. 37 or more) . Thus two species, A . boulengeri (subtropical convergence) and especially A. niger (Atlantic), may be very difficult to distinguish from the "cyaneus" group as young specimens. In both species, distinctive luminous patches are becoming well developed by a standard length of 50 mm: in A. niger on the side above the pectoral fin; in A. boulengeri on the dorsal and ventral caudal peduncle. Photophore counts are higher in A. boulengeri than in the"cyaneus" group, but overlap slightly (only at 56 for the IC count). In A. niger, counts other than dorsal-rays are almost identical with those of the "cyaneus" group, but the gradually enlarged swelling at the distal end of the barbel occupies one-third to one-half of the barbel length (in small specimens) whereas any swelling in the "cyaneus" group is shorter and less developed.
Goodyear RH, Gibbs RH, Jr. 1970. Ergebnisse der Forschungsreisen des FFS “Walther Herwig” nach Südamerika. X. Systematics and zoogeography of stomiatoid fishes of the Astronesthes cyaneus species group (Family Astronesthidae) with descriptions of three new species. Archiv für Fischereiwissenschaft 20(2/3):107–131.
To about 140 mm.
Atlantic, 23°50'N, 20°08'W, depth 0–500 meters.
Holotype: ISH 201-1966.
