The angular roughshark (''Oxynotus centrina'') is a rough shark of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Oxynotidae.

Taxonomy

Biologist

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

described the angular roughshark, ''O. centrina'', in 1758. This name was later finalized and accepted by the scientific community as the official name for the species in 1976.

Description

At birth, they are less than and they mature at about . Most records are of individuals less than , but they can reach about . Their litter size is seven or eight pups off

Angola , national_anthem = " Angola Avante"() , image_map = , map_caption = , capital = Luanda , religion = , religion_year = 2020 , religion_ref = , coordina ...

to 23 in the Mediterranean. They have ridges over their eyes that expand into large, rounded knobs, which are covered with enlarged denticles – these are absent in other species of rough sharks. They possess very large spiracles that are vertically elongated, being almost as high as the length of their eyes. Their first dorsal spine is oriented slightly forward. They feed on worms,

crustaceans Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

, and

mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

.Compagno, L., Dando, M. and Fowler, S. ''Sharks of the World''. Princeton Field Guides ''Oxynotus centrina'' has a compressed body, triangular in

cross section Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture & engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **Abs ...

, with a broad and flattened head. The snout is flat and blunt. Just like all of the ''Oxynotus'' species, they have two relatively large dorsal fins that are sail-like, and no anal fin. Their color scheme is grey or grey-brown dorsally with dark blotched on its head and sides. However, one identifying feature is the light horizontal line below the eyes on the cheek.Hurst, Richard. "Factsheet: Angular Roughshark." Factsheet: Angular Roughshark. N.p., n.d. Web. 30 November 2013. . Since it shares the northeast Atlantic with another species of ''Oxynotus'', other distinguishing features include the extremely large spiracles, their dorsal fins, and their large

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 scales, which can also provide effective camouflage through the use of reflection and colouration, as we ...

s above their eyes. Like most of the ''Oxynotus'' species, ''O. centrina'' has

lanceolate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular o ...

upper teeth and blade-like lower teeth, with 12 rows of teeth on either side. ''Oxynotus centrina'' usually moves by gliding on the bottom of the sea, sometimes hovering over the sandy or muddy surfaces of the seabed."Angular rough shark (Oxynotus centrina)." Angular rough shark videos, photos and facts. N.p., n.d. Web. 1 December 2013. .

Range and habitat

They occur in the eastern Atlantic from

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

, including the entire

Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

. They may also occur off

Mozambique Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...

. They prefer coralline algal and muddy bottoms on continental shelves and upper slopes at depths of , but occur mostly below . Studies of these sharks in the Mediterranean indicate they prefer to spend their times at depths of .

Reproduction

Male and female angular roughsharks are reported to mature at about 50–70 cm. Although, some studies have shown that females mature at a slightly larger size than males. Being an

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

species, ''O. centrina'' produces 10-12 pups usually between 21 and 24 cm in length.

Population

Some data has been gathered on this species of ''Oxynotus'' in the period from 1994 to 1999 in the

. ''O. centrina'' was only present in 0.6% of the tows during this period at a depth of 100 to 200 m. Regional indexes indicate this species is more common in the western central

and lower index in the western and eastern

. However, ''O. centrina'' was completely absent from the Eastern central

."Oxynotus centrina." (Angular Rough Shark). N.p., n.d. Web. 1 December 2013. . In 1948, trawl surveys indicated that ''O. centrina'' was once present, but uncommon, in the

Adriatic The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkans, Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) ...

. Although, the species has been absent in subsequent studies in the

, suggesting a possible extinction of that species in the area. However, recent studies, done by Lipej in 2004, show that some juveniles have been caught in the central

. Also, some data collected during the surveys in the

Balearic Sea The Balearic Sea ( endotoponym: ''Mar Balear'' in Catalan and Spanish) is a body of water in the Mediterranean Sea between the Balearic Islands and the mainland of Spain. The Ebro River flows into this small sea. Islands and archipelagoes Th ...

and the

Ionian Sea The Ionian Sea ( el, Ιόνιο Πέλαγος, ''Iónio Pélagos'' ; it, Mar Ionio ; al, Deti Jon ) is an elongated bay of the Mediterranean Sea. It is connected to the Adriatic Sea to the north, and is bounded by Southern Italy, including C ...

found one specimen at 800 m in the western

, suggesting that the population of ''O. centrina'', in the east-central

, has an unknown population. However, this species was absent in the northeast

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

in a study of deepwater

longline fishing Longline fishing, or longlining, is a commercial fishing angling technique that uses a long ''main line'' with baited hooks attached at intervals via short branch lines called ''snoods'' or ''gangions''.Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

. This is important because this species was abundant in this region until 1997.

Conservation status

''Oxynotus centrina'' is a minor

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 ...

of offshore fisheries such as trawl fleets. Although this can have a negative impact on the species, as stated above, the species had been thought extinct in the

, decreased fishing has led to their rediscovery. This species, sometimes caught by fishermen in the

, has little to no commercial value. Also, it is thought to bring bad luck to fishermen if caught and kept. When released, it has never been reported to survive. The

IUCN Red List of Threatened Species The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biologi ...

has deemed this species of ''Oxynotus'' as endangered due to consistent landings by fishermen and bycatch by deepsea fisheries.

References

{{Taxonbar, from=Q1089264 angular roughshark Marine fish of Europe Fish of the Mediterranean Sea Fish of the Black Sea Marine fauna of West Africa angular roughshark angular roughshark