The sailfin roughshark (''Oxynotus paradoxus'') is a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of
dogfish shark
Squalidae, more commonly known as dogfish, dog sharks, or spiny dogfish, are one of several families of sharks categorized under Squaliformes, making it the second largest order of sharks, numbering 119 species across 7 families. Having earned t ...
in 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
''Oxynotus'' is a genus of sharks in the order Squaliformes, commonly known as the rough sharks. It is the only extant genus in the family Oxynotidae. They live in deep waters in the Atlantic and western Pacific Oceans.
Rough sharks are small ...
, found in the eastern
North 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 and ...
from
Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
latitude
In geography, latitude is a coordinate that specifies the north south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from 90簞 at the south pole to 90簞 at the north pol ...
s 61簞N and 11簞N, at depths of between . Its length is up to .
Its reproduction is
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 ...
.
''Oxynotus paradoxus'' is thought to be a slow-moving predator of small benthic animals. The sailfin roughsharks is found near the Eastern
Atlantic ocean
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 ...
at those depths. However, it has been reported to be found on the shores of
Morocco
Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...
, recently reported in the
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North Ame ...
, and in the
Azores
)
, motto =( en, "Rather die free than subjected in peace")
, anthem= ( en, "Anthem of the Azores")
, image_map=Locator_map_of_Azores_in_EU.svg
, map_alt=Location of the Azores within the European Union
, map_caption=Location of the Azores wi ...
water. This species is an uncommon
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 bottom trawls, and is listed by the
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
(IUCN) as Vulnerable.
Taxonomy
French biologist F. Frade found this species of ''Oxynotus paradoxus''. This name was later finalized and accepted by the scientific community as the official name for the species. Frade published his findings of this specimen in 1929 in the scientific journal ''Boletim da Sociedade Portuguesa de Ci礙ncias Naturais''.FrAde F., 1929. Une nouvelle esp癡ce ou une aberration individuelle de lOxynotus centrina (Linn.). Bull. Soc. Port. Sci. Nat., 10(22): 263-267.
Description
''Oxynotus paradoxus'' is a rare shark found in the deep waters of the ocean from about 265750 m below ocean level. At birth, ''O. paradoxus'' is about 25 cm in length and can grow up to 118 cm in length. It has a compressed body form with a blunt snout and a wide, flattened head. ''O. paradoxus'' has two tall, narrow and pointed
dorsal fins
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
that contain concave trailing edges, but no
anal fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...
. The first dorsal spine trails back, a unique feature of this species of ''Oxynotus''. Both
spiracle Spiracle or spiraculum may refer to:
* Spiracle (arthropods), opening in the exoskeletons of some arthropods
* Spiracle (vertebrates), openings on the surface of some vertebrates
* Spiraculum, a genus of land snails in family Cyclophoridae
Cycl ...
s are relatively small compared to other sharks and are almost completely circular. The top teeth of ''O. paradoxus'' are
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 ...
, but the lower teeth are blade-like. Each set of both upper and lower teeth contain 12 rows of teeth.Hurst, Richard. "Factsheet: Sailfin Roughshark." Factsheet: Sailfin Roughshark. 30 November 2013. . The flank
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 contain a central cusp next to two lateral cusps and a second middle cusp above the primary cusp.Azevedo, Jose, Fernando Sousa, and Joao Brium. "Dermal denticles and morphometrics of the sailfin roughshark Oxynotus paradoxus (elasmobranchii, oxynotidae), with comments on its geographic Distribution." Cybium 27 (2003): 117-122. .
Of all the Atlantic ''Oxynotus'' species, ''O. paradoxus'' is the only species to have an incline first
dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
spine. The color of the shark when living is uniform dark brown, but it turns black in preserved specimens.
Reproduction
This species of shark is an ovoviviparous species, meaning the embryos develop inside eggs, which are retained inside the mother's body until the eggs are ready to hatch. These shark pups are about 25 cm in length.
Geographical habitat and ecology
''Oxynotus paradoxus'' lives in two separate places: 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 ...
and Easter Central Atlantic. In the Northeast Atlantic they are found along the Atlantic slope of Scotland and the
Mid-Atlantic ridge
The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North Ame ...
. In the Eastern Central Atlantic they are found from Morocco southward to the
Gulf of Guinea
The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean from Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian (zero degrees latitude and longitude) is in the ...
.
Based on the distribution of ''O. paradoxus'', occupying a bathybenthic habitat, the species can be classified as a
benthos
Benthos (), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone.benthic fish and
invertebrates
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
.
Threat and conservation
Since this species lives in the depths where deepwater fisheries operate, they can have a negative impact on the already uncommon species by being the bycatch of these offshore fisheries. Although their population is unknown, most of its population is in the deeper offshore waters and very few are in the inshore waters.
Although this shark is a bycatch by offshore fisheries, it has little to no commercial uses. When caught, the most probable use of ''O. paradoxus'' is as fishmeal or bait.