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velvet belly lanternshark
The velvet belly lanternshark (or simply velvet belly, ''Etmopterus spinax'') is a species of dogfish shark in the family Etmopteridae. One of the most common deepwater sharks in the northeastern Atlantic Ocean, the velvet belly is found from Iceland and Norway to Gabon and South Africa at a depth of . A small shark generally no more than long, the velvet belly is so named because its black underside is abruptly distinct from the brown coloration on the rest of its body. The body of this species is fairly stout, with a moderately long snout and tail, and very small gill slits. Like other lanternsharks, the velvet belly is bioluminescent, with light-emitting photophores forming a species-specific pattern over its flanks and abdomen. These photophores are thought to function in counter-illumination, which camouflages the shark against predators. They may also play a role in social interactions.
Young velvet bellies feed mainly on krill and small bony fish, transitioning to squid and shrimp as they grow larger. There is evidence that individuals also move into deeper water as they age. This species exhibits a number of adaptations to living in the deep sea, such as specialized T-cells and liver proteins for dealing with the higher concentrations of heavy metals found there. Velvet bellies often carry a heavy parasite load. It is ovoviviparous, giving birth to litters of six to 20 young every two to three years. This species has virtually no commercial value, but large numbers are caught as bycatch in deepwater commercial fisheries. Although it has been assessed as of Least Concern by the International Union for Conservation of Nature, the heavy fishing pressure throughout its range and its slow reproductive rate are raising conservation concerns.
==Taxonomy==
The velvet belly was originally described as ''Squalus spinax'' by Swedish natural historian Carl Linnaeus, known as the "father of taxonomy", in the 1758 tenth edition of ''Systema Naturae''. He did not designate a type specimen; the specific epithet ''spinax'' is in reference to the spiny dorsal fins. This species was later moved to the genus ''Etmopterus'' via the synonymy of Constantine Samuel Rafinesque's ''Etmopterus aculeatus'' with ''Squalus spinax''.
The velvet belly is grouped with the Caribbean lanternshark (''E. hillianus''), fringefin lanternshark (''E. schultzi''), brown lanternshark (''E. unicolor''), broadbanded lanternshark (''E. gracilispinis''), combtooth lanternshark (''E. decacuspidatus''), and dwarf lanternshark (''E. perryi'') in having irregularly arranged, needle-shaped dermal denticles. Its common name comes from this shark's black ventral surface, which is sharply delineated from the rest of its body like a patch of velvet.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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