As in other deep-sea anglerfish families, sexual dimorphism is extreme: the largest females may exceed lengths of 60 cm (two feet) and are globose in shape, whereas males do not exceed 4 cm (1.5 inches) as adults and are comparatively fusiform. Their flesh is gelatinous, but thickens in the larger females, which also possess a covering of “bucklers” — round, bony plates each with a median spine — that are absent in males. Both are a reddish brown to black in life.
In females, the mouth is large and oblique. The subequal jaws are anteriorly lined with rows of numerous closely-set, depressible, and retrorse teeth; vomerine teeth are absent. Footballfish females differ from those of other ceratioid families by their shortened, blunt snout; along with the chin, it is covered in sensory papillae. Originating above or slightly in advance of the smalleye is an ilicium (the “fishing rod”) and at its end a bioluminescent, bulbous esca (the “fishing lure”, its light owing to symbiotic bacteria). Escal morphology varies between species, and it may or may not possess denticles or accessory appendages, the latter either branched or unbranched. The pterygiophore of the ilicium does not protrude from the snout, and there is no hyoid barbel.
At maturity, the streamlined males have an enlarged posterior nostril (with 10 – 17 lamellae); slightly ovoid eye with an enlarged pupil creating a narrow anterior aphakic space; no ilicium or esca; and the head and body is covered in dermal spinules, those along the snout midline being enlarged. The jaw lacks teeth, whereas those of the denticular bone have fused into a larger mass; the upper denticular bone possesses 10 – 17 hooked denticles.
In both sexes, the fins are spineless: the single dorsal fin with 5 – 6 soft rays, the pectoral fins with 14 – 18, the anal fin with four, and thecaudal fin with 19. There are six branchiostegal rays and 19 vertebrae; the parietal is lacking throughout life, there are no epurals, and thepelvic bone is triradiate.
(From Wikipedia.org, June 20 2010)
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