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SHARPNOSE SEVENGILL SHARK
Order - Hexanchiformes
Family - Hexanchidae
Genus - Heptranchias
Species - perlo
Sharpnose sevengill shark

Taxonomy

The sharpnose sevengill shark was described as Heptranchias perlo by Bonnaterre in 1788. The genus name Heptranchias is derived from the Greek "heptra" meaning seven arms and "agchein" meaning throttle. Synonyms used in past scientific literature to refer to this species include Heptranchias cinereus Gmelin 1789, Squalus cinereus Gmelin 1789, Notidanus cinereus Gmelin 1789, Heptrancus angio Costa 1857, Heptranchias angio Costa 1857, Notidanus cinereus aetatis Bellotti 1878, Notidanus cinereus pristiurus Bellotti 1878, Heptranchias deani Jordan & Starks 1901, and Heptranchias dakini Whitley 1931.


Common Names

English common names include sharpnose sevengill shark, one-finned shark, perlon shark, sevengill cow shark, sevengilled Mediterranean shark, sevengilled shark, sharpnose seven-gill shark, snouted sevengill shark and slender sevengill shark. Other common names are albafar bravo (Portuguese), alcatriña (Spanish), aletre (Greek), angiolo (Italian), archote (Portuguese), Aschfarbener Siebenspalthai (German), bico doce (Portuguese), boca-doce (Portuguese), bocadul (Spanish), bocadulce (Spanish), cação (Portuguese), cañabota bocadulce (Spanish), chien de mer (French), edo-aburazame (Japanese), eftakarcharias (Greek), epta carcharias (Greek), jian wen qi sai shi (Mandarin Chinese), kalb (Arabic), Kammzähner (German), kapeapäähai (Finnish), kelb bhar (Arabic), kko-ri-gi-rum-sang-o (Korean), monge gris (French), morruna (Maltese), mounge (French), murruna (Italian), notidano cinereo (Italian), oküz baligi (Turkish), olho-branco (Portuguese), pärlhaj (Swedish), pas glavonja (Serbian), peix volohja (Serbian), perlon (Grench), perlon (German), pesciu angiu (French), pesciu boiu (French), pesciu mansu (French), peshkagen me dhembe (Albanian), qarsh (Arabic), requin perlon (French), requin-griset (French), sharp sheva-zim (Hebrew), siebenkiemiger kammzähner (German), skerpneus-sewekiefhaai (Afrikaans), spitssnuitzevenkieuwshaai (Dutch), spitzkopfsiebenkiemer (German), squalo manzo (Italian), tiburón de 7 branchias (Spanish), tubarão-de-sete-guelras (Portuguese), and yediyariklicanavar baligi (Turkish).


Geographical Distribution

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.

World distribution map for the sharpnose sevengill shark


Habitat

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.


Biology

Sharpnose sevengill shark illustration
source Field Guide to Eastern Pacific and Hawaiian Sharks, U.S. Fish and Wildlife Service 1967


· Distinctive Features
The moderately small sharpnose sevengill shark has a slender, fusiform body with a narrow, pointed head, large green eyes and a long narrow mouth.

The sharpnose sevengill shark has a narrow head with large eyes
© George Burgess



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. There is only one small dorsal fin which originates over the inner margins of the pelvic fins. The front edge of the dorsal fin is either straight or slightly convex while the apex is rounded and rear edge concave. The anal fin is also small in size with nearly straight edges, originating under the posterior end of the base of the dorsal. The pectoral fin is small with a weakly convex outer margin and narrowly rounded apex. The caudal axis is just slightly raised with a convex upper margin and a subterminal notch on the lower margin.

Sharpnose sevengill shark dorsal fin placement and caudal fin
© George Burgess



The sharpnose sevengill shark may be confused with the broadnose sevengill shark (Notorynchus cepedianus). The broadnose sevengill shark has small eyes and a broad, rounded snout in contrast to the large eyes and narrow and pointed snout of the sharpnose sevengill shark. The broadnose sevengill shark also has black spots over its entire body in contrast to the sharpnose sevengill shark that lacks this coloration.


Sharpnose sevengill shark
courtesy National Marine Fisheries Service


· Coloration
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.


Sharpnose sevengill shark teeth from lower jaw
© Cathleen Bester/Florida Program for Shark Research


Sharpnose sevengill shark dentition illustration and photograph
Bigelow & Schroeder (1948)/© George Burgess


·Dentition
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.


Sharpnose sevengill shark dermal denticles
Bigelow & Schroeder (1948) FWNA

Sharpnose sevengill shark denticles

·Denticles
The dermal denticles overlap closely. Each denticle is longer than broad with a larger median tooth followed by a pair of smaller lateral teeth. The median ridge is distinct. The denticles are very thin and transparent, allowing the pigmentation of the skin to be visible. The denticles along the upper edge of the caudal fin are ovoid and lack marginal teeth. Three longitudinal ridges are present, forming a poorly defined crest.


Sharpnose sevengill sharks grow to a maximum length of 4.5 feet (1.40 m)
© George Burgess


·Size, Age, and Growth
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.


· Food Habits
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.


Sharpnose sevengill shark embryo
Bigelow & Schroeder (1948)


· Reproduction
The sharpnose sevengill shark is an ovoviviparous species. There appears to be no set reproductive season. Following gestation, from 9-20 pups are born in each litter. Each newborn pup measures approximately .8 feet (.25 m) in length.


· Predators
Large sharks are potential predators of the sharpnose sevengill shark.


· Parasites
Nematodes including Anisakis sp. and Contracaecum sp. are documented parasites of this shark. Other species of nematodes have been reported from the stomach mucus of the sharpnose sevengill shark. Crossobothrium dohrnii, is among the many parasitic cestodes found in the intestine of this shark.



Importance to Humans

Although of only minor commercial fishery interest, the sharpnose sevengill shark is caught primarily as bycatch in fisheries using bottom trawls and longlines. In waters off North America, it occurs in such low numbers that it is of no economic importance.


Danger to Humans

The sharpnose sevengill shark is considered harmless to humans. However, care must be taken when landing this shark as it is aggressive and will attempt to bite its captors. The flesh is mildly poisonous to humans when consumed.


Conservation

Although this species is of minor commercial importance, bycatch in bottom trawls and longline fisheries may cause future decline of populations. The species is currently assessed as "Near Threatened" by the World Conservation Union (IUCN). The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.





Prepared by:

Cathy Bester