The sharpnose sevengill shark (''Heptranchias perlo''), also known as one-finned shark, perlon shark, sevengill cow shark, sharpsnouted sevengill or slender sevengill, is a species of

shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...

in the family Hexanchidae, and the only living species in the genus ''Heptranchias''. Found almost circumglobally in deep water, it is one of the few species of sharks with seven pairs of

gill slit Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In c ...

s as opposed to the usual five. The other shark species with seven gill slits is the broadnose sevengill shark. Though small, this shark is an active, voracious predator of

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s and

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

. When caught, this species is notably defensive and will attempt to bite. It is of minor commercial importance.

Taxonomy

The genus name ''Heptranchias'' is from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''heptra'' meaning "seven arms", and ''agchein'' meaning "throttle", referring to this shark's seven pairs of gill slits. Other

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

s for this species include one-finned shark, perlon shark, sevengill cow shark, sevengilled Mediterranean shark, sevengilled shark, sharpnose seven-gill shark, snouted sevengill shark and slender sevengill shark.Bester, C
Biological Profiles: Sharpnose Sevengill Shark
''Florida Museum of Natural History Ichthyology Department''. Retrieved on February 16, 2009. Some authors believe this species is distinct enough to merit its own family, Heptranchiidae.

Distribution and habitat

The sharpnose sevengill shark is uncommon, but widely distributed in the

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

regions of all oceans except for the northeastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

. It is found from

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, including the northern

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

, and from

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Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

in the western

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

. In the eastern Atlantic, it occurs from

Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

, including the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

. It is reported from the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

off southwestern

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

, Aldabra Island, southern

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, and

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. In the Pacific Ocean, it is known from

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, and northern

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. This is a

demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer o ...

to semipelagic species usually captured at a depth of , but is occasionally found close to the surface (though these reports may represent misidentifications) or down to . It is mainly found on the outer

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

and upper

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...

, and may aggregate around

seamount A seamount is a large submarine landform that rises from the ocean floor without reaching the water surface (sea level), and thus is not an island, islet, or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly a ...

Description

Usually measuring long, sharpnose sevengill sharks attain a maximum length of . This species has a slender,

fusiform Fusiform (from Latin ''fusus'' ‘spindle’) means having a spindle (textiles), spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon (geometry), lemon-shape, but often implies a focal broadening of a ...

body with a narrow, pointed head. The

eyes An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

are very large and

fluoresce Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

green in live specimens. The

mouth A mouth also referred to as the oral is the body orifice through which many animals ingest food and animal communication#Auditory, vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also t ...

is narrow and strongly curved, containing 9–11

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

on either side of the

upper jaw In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxillar ...

and five teeth on either side of the

lower Lower may refer to: * ''Lower'' (album), 2025 album by Benjamin Booker *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is sit ...

. The upper teeth are narrow and hook-shaped with small lateral

cusp A cusp is the most pointed end of a curve. It often refers to cusp (anatomy), a pointed structure on a tooth. Cusp or CUSP may also refer to: Mathematics * Cusp (singularity), a singular point of a curve * Cusp catastrophe, a branch of bifu ...

s, while the lower teeth are broad and comb-shaped (except for a symmetrical symphysial tooth). Unlike most other sharks, there are seven pairs of gill slits that extend onto the throat. A single small

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

is located behind the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

s, with a straight front margin, narrowly rounded tip, and concave rear margin. The

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

s are small with a weakly convex outer margin. The

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

is small with nearly straight margins. The

caudal peduncle Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

is long, and the distance between the dorsal fin origin and the

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

is more than twice the dorsal fin base. The closely overlapping

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scale (zoology), scales, which can also provide effective Underwater camouflage, camouflage through the us ...

s are very thin and transparent; each is longer than it is broad, bearing a distinct median ridge and two lateral ridges ending in marginal teeth. The coloration is brownish gray to olive above and lighter below; some individuals have dark blotches on the body or light posterior fin margins. Juveniles have dark blotches on the flank and dark tips on the dorsal fin and upper caudal lobe. Heptranchias perlo head.jpg, Head Heptranchias perlo jaws.jpg, Jaws Heptranchias perlo upper teeth.jpg, Upper teeth Heptranchias perlo lower teeth.jpg, Lower teeth

Biology and ecology

Despite its relatively small size, the sharpnose sevengill shark is considered a

top predator An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...

in the ecosystem it inhabits. At the Great Meteor Seamount in the eastern Atlantic, this species feeds primarily on

teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

s and

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

s, and to a lesser extent on small

cartilaginous fish Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeleto ...

es. Off

Tunisia Tunisia, officially the Republic of Tunisia, is a country in the Maghreb region of North Africa. It is bordered by Algeria to the west and southwest, Libya to the southeast, and the Mediterranean Sea to the north and east. Tunisia also shares m ...

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s are the second-most common prey taken after teleosts. Off Australia, this species consumes mostly teleosts, with smaller individuals taking mainly '' Lepidorhynchus denticulatus'' and larger individuals taking increasing numbers of snake mackerels and

cutlassfish The cutlassfishes are about 45 species of predatory ray-finned fish in the family Trichiuridae of the order Scombriformes found in seas throughout the world. Fish of this family are long, slender, and generally steely blue or silver in colour, ...

es. It is a strong-swimming species, with feeding and activity level increasing at night. This species may be preyed upon by larger sharks. Known

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

s of the sharpnose sevengill shark include

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

s in the genera ''

Anisakis ''Anisakis'' ( ) is a genus of parasitic nematodes that have life cycles involving fish and marine mammals. They are infective to humans and cause #Anisakiasis, anisakiasis. People who produce immunoglobulin E in response to this parasite may su ...

'' and ''Contracaecum'', and the

cestode Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, commonly known as tapeworms. Their bodies co ...

''Crossobothrium dohrnii''. Reproduction is

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a "bridging" form of reproduction between egg-laying oviparity, oviparous and live-bearing viviparity, viviparous reproduction. Ovoviviparous animals possess embryos that develo ...

, with no apparent reproductive season. The females give birth to litters of 9–20 pups; the

newborn In common terminology, a baby is the very young offspring of adult human beings, while infant (from the Latin word ''infans'', meaning 'baby' or 'child') is a formal or specialised synonym. The terms may also be used to refer to Juvenile (orga ...

s measure about long. Males mature at long and females at . The onset of sexual maturation in males may be marked by the formation of

mucus Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...

on the tips of the

claspers In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's c ...

Relationship to humans

The sharpnose sevengill shark is reasonably small and is located in generally deep water, and these characteristics classify this shark as harmless to humans. Small to moderate numbers of sharpnose sevengill sharks are captured as

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

in certain deepwater

commercial fisheries Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often p ...

on longlines or in

trawl Trawling is an industrial method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch di ...

s. They are used for

fishmeal Fish meal (sometimes spelled fishmeal) is a commercial product made from whole wild-caught fish, bycatch, and fish by-products to feed farm animals, such as pigs, poultry, and farmed fish.R. D. Miles and F. A. Chapman.FA122: The Benefits of Fish ...

and liver oil; the

meat Meat is animal Tissue (biology), tissue, often muscle, that is eaten as food. Humans have hunted and farmed other animals for meat since prehistory. The Neolithic Revolution allowed the domestication of vertebrates, including chickens, sheep, ...

is said to be of good quality, but the flesh is considered to be mildly poisonous when consumed. When captured, it is very active and quick to bite, but it does not pose a substantial threat to people due to its small size. It has occasionally been kept in captivity in

Conservation status

Some concern exists that populations of this slow-reproducing species may be declining in areas of sustained deepwater fishing, and it has been assessed as

Near Threatened A near-threatened species is a species which has been Conservation status, categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature (IUCN) as that may be vulnerable to Endangered species, endangerment in the ne ...

by the

World Conservation Union The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the statu ...

. In June 2018 the New Zealand Department of Conservation classified the sharpnose sevengill shark as "At Risk – Naturally Uncommon" with the qualifiers "Data Poor" and "Secure Overseas" under the

New Zealand Threat Classification System The New Zealand Threat Classification System is used by the Department of Conservation to assess conservation priorities of species in New Zealand. The system was developed because the IUCN Red List, a similar conservation status system, had s ...

References

{{Taxonbar, from=Q1126774 Heptranchias Fish described in 1788