The brown lanternshark or bristled lanternshark is a little-known species of deep-sea dogfish shark in the family Etmopteridae. It is found off Japan and New Zealand, and possibly also South Africa and Australia, typically deeper than. This species can be distinguished from other lanternsharks by its coloration, which is a uniform dark gray or brown without the ventral surface being much darker and clearly delineated from the rest of the body. The brown lanternshark feeds on small bony fishes, cephalopods, and crustaceans. Reproduction is ovoviviparous, with females giving birth to 9-18 young. An unusually high proportion of individuals in Suruga Bay are hermaphrodites, with both male and female characteristics.
Confirmed specimens of the brown lanternshark have been captured from off southern Honshu, Japan, and around New Zealand. If E. compagnoi and E. sp. B are also considered, then the known range of this species is extended to off South Africa and southern Australia. The brown lanternshark inhabits continental shelves and seamounts at a depth of, though is most common below. It is generally found deeper than other lanternsharks that share its range, and may have midwater habits.
Description
The brown lanternshark has a robust, almost cylindrical body with a wide, flattened head. Around 28 tooth rows are in the upper jaw and 34 tooth rows are in the lower jaw. The upper teeth have a pointed central cusp flanked by fewer than three pairs of lateral cusplets, while the bottom teeth are large and tipped with a strongly angled triangular cusp. The five pairs of gill slits are relatively large. The first dorsal fin is low with a minute leading spine; the second dorsal fin is twice as high as the first with a much larger spine. The caudal peduncle is short, leading to a long caudal fin with the upper lobe much larger than the lower. The dermal denticles of this shark are tiny and densely placed with no regular pattern; each denticle has a four-cornered base and rises to a narrow, slightly curved point. The denticles of females are firmly attached, while those of males are easily removed. The coloration is a plain dark gray or brown, slightly darker below and lighter on the dorsal fin margins. Unlike other lanternsharks, there is a not a sharp contrast between the dorsal and ventral colors. There is a horizontal black line on the base of the tail, and another fainter black mark over the pelvic fins. The maximum reported length is for males and for females.
Biology and ecology
The most important prey of the brown lanternshark are bony fishes, followed by cephalopods, and finally crustaceans. A known parasite of this shark is a species of copepod in the genus Lerneopoda. Like other lanternsharks, the brown lanternshark is ovoviviparous, meaning the young hatch inside the mother's uterus and are sustained by a yolk sac. The litter size is 9-18. Newborns measure in length. Males reach sexual maturity at a length of, and females at a length of. A study of brown lanternsharks in Suruga Bay by Yano and Tanaka found a 23% prevalence of hermaphroditism within the population. Of the 16 hermaphrodites examined, 15 were functional females that also possessed well-developed claspers, while one was a functional male with ovarian tissue in the left testis. The reason why so many sharks in Suruga Bay are hermaphroditic is unclear, but has been speculated to relate to pollution.
