Linophryne macrodon Regan 1925

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Dorsal profile of frontals angular, but without spine; sphenotic, preopercular, and angular spines similar to those of females of similar size of other species of subgenus; teeth in each premaxillary 7–17, arranged in four series; teeth in each dentary 8–11, arranged in three series, longest tooth in fully metamorphosed specimens 14–19% SL; one or two pairs of vomerine teeth; dorsal-fin rays 3; anal-fin rays 3; pectoral-fin rays 15–17.

Metamorphosed females with length of illicium 26–37% SL, shorter in metamorphic specimens; distal escal filament simple in holotype, with a rudimentary pair of filaments at base in three metamorphic females, two pairs of filaments in three largest specimens; six of seven specimens with lateral escal filaments very similar, most branching to form as many as six secondary filaments, length of each (median and longest pair of filaments 1–1.5 times escal diameter) slightly increasing with increasing standard length; sixth specimen (41-mm) with filaments somewhat longer (longest about 3 times diameter of escal bulb) and more highly branched, each forming 8 to about 25 secondary filaments.

Length of barbel increasing from 24–32% SL in metamorphic specimens to 65–80% SL in metamorphosed specimens; divided portion of stem of barbel 10–14% SL in metamorphic specimens, 18–27% SL in metamorphosed specimens; branching very similar in all specimens; proximal posterior branch simple with a distal series of 2–6 internal photophores; metamorphic specimens with anterior branch simple except for tiny rudiments of lateral branches; metamorphosed specimens with anterior branch divided distally into 3 or 4 secondary branches, some further divided to form a cluster of 7–10 slender tapering filaments, each with a series of few to about 20 photophores; distal pair of primary branches of unequal length, bearing a few rudimentary lateral branches in metamorphic specimens, of nearly equal length in metamorphosed specimens, each divided distally to form a terminal cluster of 2–5 slender filaments, longest with a series of 25–30 photophores.

A dense concentration of subdermal pigment on caudal peduncle.

Single known parasitic male, 21.5 mm, with pointed sphenotic spines, attached to largest known female, 91 mm, with immature eggs each about 0.1 mm in diameter.

Metamorphosed females of Linophryne macrodon differ from those of all other species of the genus in having the following escal and hyoid barbel characters: escal bulb without distal prolongation; a single distal filament and three pairs of lateral filaments, all branched except in juveniles; anterior and posterior escal appendages absent. Length of barbel 24–80% SL, with stem unbranched and distal half to two-thirds gradually dividing into three primary branches, each terminating into 1–4 tapering, branched or simple filaments, each with a series of few to 25–30 internal photophores. A dense concentration of subdermal melanophores on caudal peduncle. Males with pointed sphenotic spines.

The holotype of Linophryne macrodon was caught in the Gulf of Panama, but the six additional known specimens were all taken in the Western North Atlantic between about 24 and 39°N, west of 63°W.

Bathypelagic, demersal. All specimens have been caught in various non-closing nets with maximum fishing depths exceeding 1000 m, except for the 41-mm specimen taken in a bottom haul at only 300 m.

Pietsch TW. 2009. Oceanic Anglerfishes: Extraordinary Diversity in the Deep Sea. Berkley: University of California Press. 638 p.

Parasitized females have a single attached male, in contrast to the linophrynid genera Haplophryne and Borophryne (and the ceratiid genera Ceratias and Cryptopsaras) in which females with two or more males are known. In all known cases parasitized females of the family, the male is directed forward with respect to the female and attached in nearly the same position on the ventral midline of the female, somewhat in front of and below the sinistral anus; with only one or two exceptions, all are attached upside down with respect to the female. This is again in contrast to the linophrynid genera Haplophryne and Photocorynus (and the ceratiid genus Cryptopsaras) in which males may attach in any direction and almost anywhere on the head and body of the female. In all known examples, the males are attached by both upper and lower jaws, leaving prominent openings on each side that lead into their mouths and opercular cavities; there is no papilla of tissue projecting from the female into the mouth of the male.

Known from 10 metamorphosed females (19–91 mm), including two tentatively assigned specimens (28–28.5 mm); and one parasitic male (21.5 mm).

DANA station 1208(4), Gulf of Panama, 6°48'N, 80°33'W, open pelagic net, 3500 m of wire, 0810 m, 16 January 1922.

Holotype of Linophryne macrodon: ZMUC P92144, 37 mm.