BRISTLED LANTERNSHARK OR BROWN LANTERNSHARK
The Bristled lanternshark or Brown lanternshark (Etmopterus unicolor) is a little-known species of deep-sea shark belonging to the family Etmopteridae. It is found off the southeast Atlantic and western Indian Ocean in Japan, New Zealand and possibly South Africa and Australia, typically deeper than 1,319 feet. They can be distinguished from other lanternsharks by its coloration, which is a uniform dark gray or brown to black without the ventral surface being much darker and clearly delineated from the rest of the body. A select population of the Bristled lanternshark or Brown lanternshark are hermaphrodites. Research is still underway to discover why these sharks have adapted in this way.
Family: Etmopteridae – Lantern Sharks
Common Name– Dogfish Sharks
Common Name– Lantern Sharks
Status: IUCN Red List DATA DEFICIENT
Average Size and Length: They are born around 17 cm/7 inches. Mature males are around 53 cm/2 feet. The maximum recorded was a female at 69 cm/2.3 feet.
Teeth and Jaw: The teeth in the upper and lower jaws differ. There are round 28 tooth rows in the upper jaw and 34 tooth rows are in the lower jaw. The upper teeth have a pointed central cusp flanked with 3 pairs of lateral cusplets, while the bottom teeth are large and tipped with a strongly angled triangular cusp. They are much broader.
Head: The head is wide and flat, and the eyes are big and closer to the snout than the first gill slit.
Denticles: There are bristle-like lateral trunk dermal denticles with slender, hooked conical crowns. The dermal denticles are not arranged in rows. They are irregular over the surface. They do cover the snout.
Demographic, Distribution, Habitat, Environment and Range: The range of the Bristled lanternshark or Brown lanternshark is tentative. The can be found off the southeast Atlantic and western Indian Ocean in South Africa and possibly southern Namibia. They can be found in the west Pacific in Japan and possibly southern Australia and New Zealand. They can be found over continental slopes and seamounts between 1,319-4,528 feet.
Diet: They are thought to feed on small bony fishes, cephalopods, and crustaceans.
Aesthetic Identification: The Bristled lanternshark or Brown lanternshark is large, robust and somewhat cylindrical. Like its name, it is grey-brown, or dark brown or brownish-black in color. The ventral side is darker. There are broad distinct elongated caudal markings on the tail. There are indistinct pelvic flank marking. The gill slits are long. They are about half the eye length. The first dorsal fin is long and low, and the grooved fin spine is short. The second dorsal fin is about twice the height of the first dorsal fin with a strong spine. The fin area is about half as large as the first.
Biology and Reproduction: They are presumably ovoviviparous with implications that they may give birth to between 9-18 pups per litter. Males are thought to reach sexual maturity at a length of 18 inches, and females at a length of 20 inches. There is research that concludes a portion of the population in Suruga Bay are hermaphrodites. Yano and Tanaka (1989) found a 23% prevalence of hermaphroditism within the population. Of the 16 hermaphrodites examined, 15 were functional females (and some were pregnant) that also possessed well-developed claspers (male intromittent organs), 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. (Yano, K. & Tanaka, S. (September 1989). “Hermaphroditism in the lantern shark Etmopterus unicolor (Squalidae, chondrichthyes)“. Ichthyological Research. 36 (3): 338–345.)
There are copepod parasites.
Behavioral Traits, Sensing and Intelligence: The Bristled lanternshark or Brown lanternshark may swim in midwater.
Bristled Lanternshark or Brown Lanternshark Recorded Attacks on Humans: Not a threat to humans.