Sharpnose Sevengill Shark

Sharpnose Sevengill Shark The moderately small sharpnose sevengill shark (Heptranchias perlo) has a slender, fusiform body with a narrow, pointed head, large green eyes and a long narrow mouth. It has seven pairs of gill slits in contrast to the five gills that most sharks possess. These gill opening extend down onto the throat.

Coloration of the sharpnose sevengill shark is brownish grey to olive on the dorsal surface, paling to a lighter ventral surface. Adults may have indistinct pale posterior margins on all fins as well as faint dark blotches on the body. Live specimens have large fluorescent green eyes. Juveniles may have dark blotches in the flank area as well as dark tips on the dorsal and caudal fins.

The smallest hexanchoid shark, the sharpnose sevengill shark grows to a maximum length of 4.5 feet (1.37 m) total length for males and 4.6 feet (1.40 m) total length for females. However, this species is more commonly observed at lengths of 2-4 feet (.6-1.2 m). Males reach maturity at 2.4-2.8 feet (.75-.85 m) total length and females reach maturity at slightly larger sizes of 3.0-3.3 feet (.9-1.0 m) total length. Biologists have observed formation of mucus on the tips of the claspers on mature and subadult males. It is believed this indicates the onset of maturity and perhaps sexual activity.

The first 3 or 4 teeth in the upper jaw are narrow with a hook-like cusp and small lateral cusps. The subsequent teeth have one or two small cusps. The teeth in the lower jaw are broad and comb-shaped with the exception of a small symmetrical tooth located at the symphysis. There are 9-11 teeth on each side of the upper jaw and 5 teeth on each side of the symphysial tooth on the lower jaw.

As a deepwater species, the sharpnose sevengill shark lives in waters on outer continental and insular shelves at depths from 89-3,280 feet (27-1000 m). It is usually found on or near the bottom, although on occasion it is observed close to the surface. Its wide distribution range suggests that the sevengill shark is probably a strong swimmer.

Distributed in tropical and temperate regions, the range of the sharpnose sevengill shark is almost circumglobal with the exception of the northeast Pacific Ocean. In the western Atlantic Ocean, this shark is distributed from North Carolina (U.S.) and northern Gulf of Mexico to Cuba and from Venezuela south to Argentina, and in the eastern Atlantic from Morocco to Namibia, including the Mediterranean Sea. The sharpnose sevengill shark is also found in the Indian Ocean in waters off southwestern India, Aldabra Island, southern Mozambique, and South Africa. Distribution in the Pacific Ocean occurs from Japan to China, Indonesia, Australia, and New Zealand as well as off the coast of northern Chile.

Although this shark is rather small in size, it is a voracious predator. As a generalist, it feeds on marine invertebrates including shrimp, crabs, lobsters, squid and cuttlefish as well as small bony fish, such as hake, and small sharks and rays. Feeding and activity increases during the night time hours.


 
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