Tadpole dogfish

Tadpole dogfish
	Tadpole dogfish ( Cephalurus cephalus )
Systematics
without rank:	Sharks (selachii)
Superordinate :	Galeomorphii
Order :	Ground Sharks (Carcharhiniformes)
Family :	Pentanchidae
Genre :	Cephalurus
Type :	Tadpole dogfish
Scientific name of the genus
	Cephalurus
	Bigelow & Schroeder , 1941
Scientific name of the species
	Cephalurus cephalus
	( Gilbert , 1892)

The tadpole dogfish ( Cephalurus cephalus ), known in the English-speaking world as the lollipop catshark , is the only species of its genus within the Pentanchidae . He lives in the area of the deep sea of the outer continental shelf and upper continental slope in the Gulf of California and in the sea area off Baja California (Baja California). The shark reaches a body length of about 24 centimeters and has a characteristic build with a large, round head and a narrow body, which makes it look like a tadpole . The large head contains greatly enlarged gills , which probably developed as an adaptation to the oxygen-poor conditions in the area of the deep sea floor.

The shark feeds mainly on crustaceans and small bony fish. It is viviparous, with the females carrying their eggs in pairs in the body and the young sharks hatching there ( ovoviviparous ).

features

The tadpole dogfish reaches an average body length of around 24 centimeters and a maximum length of up to 28 centimeters. It got its name because of its striking tadpole-like shape with a greatly enlarged head with a correspondingly large gill region and a slender body that tapers towards the tail. The body color is evenly brown, whereby the edges of the dorsal, pectoral and pelvic fins can have lighter to white edges. The eyes are iridescent green.

The head of the shark is very broad, flattened and rounded. It makes up about a third of the body length of the adult animal. The muzzle is short and blunt, the nostrils are large and equipped with medium-sized skin flaps. The mouth has a pair of pits at the corners of the mouth that encompass the corner of the mouth from the upper to the lower jaw. The widely spaced teeth have a large central tooth tip that is surrounded by one to three adjacent tips. The upper teeth are straight while the lower teeth are slightly curved outwards. There are numerous small papillae on the tongue and the roof of the mouth, and a light-colored membrane frames the interior of the mouth. The large eyes are oval, behind them are the significantly enlarged injection holes . The five gill slits are very clearly formed and strongly arched in front.

The shark's body is very soft and almost jelly-like. Unlike most other cat sharks, the first dorsal fin is well in front of the attachment of the pelvic fins. The second dorsal fin is about as long and slightly lower than the first and is opposite the anal fin. The dorsal, ventral and anal fins have a convex leading edge and a straight trailing edge. The pectoral fins are angular and about twice as long as they are wide. They start below the fourth cleft gill. The caudal fin is low with an indistinct lower lobe and a shallow notch near the tip of the upper lobe. The skin is thin and covered with thorn-like placoid scales and narrow, hair-like teeth that become more numerous on the back.

distribution and habitat

Distribution area of the tadpole cat shark

The distribution area of the tadpole dogfish is on the Gulf of California and the sea area off Baja California limited (Baja California). It lives benthically , i.e. in the area of the sea floor, on the outer continental shelf and on the upper continental slope at depths of 155 to 937 meters.

Way of life

The greatly enlarged gill region with the large gill leaves of the tadpole cat shark suggest an adaptation to a way of life on the sea floor of the deep sea with a very low oxygen content as well as high temperatures and high salinity. The shark feeds mainly on crustaceans and small bony fish .

The tadpole dogfish, unlike most other dogfish, is viviparous ( ovoviviparous ); the females give birth to their offspring in summer. They have two functioning ovaries and form thin-skinned egg capsules in pairs, which are held within the fallopian tubes until the young sharks hatch , whereby the young animals feed on the yolk inside the egg . The newborn sharks are about 10 centimeters long. The sharks reach sexual maturity with a length of about 19 centimeters.

Evolution and systematics

The lollipop catshark was the American 1892 ichthyologist Charles Henry Gilbert as Catulus cephalus in the 14th edition of the Proceedings of the United States National Museum firstdescribed . His description was based on a sexually mature male shark with a body length of 24 centimeters, the one at a depth of 841 meters off Clarión , an island of the Revillagigedo Islands southeast of Baja California. In 1941 Henry F. Bigelow and William C. Schroeder established the new genus Cephalurus for this species.

In addition to this species, there is another, so far undescribed species of the genus in the area off Panama , Peru and Chile , which differs slightly from the tadpole dogfish in its characteristics and is accordingly referred to as the southern tadpole dogfish ( Cephalurus sp. A).

On the basis of morphological and molecular biological data, the genus Cephalurus , originally assigned to the cat sharks (Scyliorhinidae), forms a common taxon with the sharks of the genera Asymbolus , Parmaturus , Galeus and Apristurus and was therefore placed in the family Pentanchidae .

Relationship with people

The tadpole dogfish is of no importance for fishing. The International Union for Conservation of Nature (IUCN) does not have an assessment of the populations or the endangerment of the species .

supporting documents

↑ ^a ^b ^c ^d ^e ^f ^g Compagno, LJV: Sharks of the World: An Annotated and Illustrated Catalog of Shark Species Known to Date . Food and Agricultural Organization, Rome 1984, ISBN 9251013845 , pp. 305-306.
^ ^A ^b ^c ^d Leonard Compagno, Marc Dando, Sarah Fowler: Sharks of the World. Princeton Field Guides, Princeton University Press, Princeton and Oxford 2005; Page 222. ISBN 978-0-691-12072-0 .
^ ^A ^b ^c Mathews, CP and MF Ruiz D .: Cephalurus cephalus, a Small Shark, Taken in the Northern Gulf of California, with a description . In: Copeia . 1974, No. 2, June 13, 1974, pp. 556-560.
↑ ^a ^b ^c ^d Bigelow, HB and WC Schroeder: Cephalurus, a New Genus of Scyliorhinid Shark with Redescription of the Genotype, Catulus cephalus Gilbert . In: Copeia . 1941, No. 2, July 8, 1941, pp. 73-76.
^ Compagno, LJV : Alternative life-history styles of cartilaginous fishes in time and space . In: Environmental Biology of Fishes . 28, No. 3, 1990, pp. 3-75.
↑ Cortés, E .: Standardized diet compositions and trophic levels of sharks . In: ICES Journal of Marine Science . 56, 1999, pp. 707-717.
↑ Balart, EF, J. González-García and C. Villavicencio-Garayzar: Notes on the biology of Cephalurus cephalus and Parmaturus xaniurus (Chondrichthyes: Scyliorhinidae) from the west coast of Baja California Sur, México . In: Fishery Bulletin . 98, 2000, pp. 219-221. ( PDF )
↑ ^a ^b Tadpole dogfish on Fishbase.org (English)
^ Iglésiasa, SP, G. Lecointre and DY Sellos: Extensive paraphylies within sharks of the order Carcharhiniformes inferred from nuclear and mitochondrial genes . In: Molecular Phylogenetics and Evolution . 34, 2005, pp. 569-583.

Web link

Cephalurus cephalus inthe IUCN 2013 Red List of Threatened Species . Posted by: Valenti, SV, 2008. Retrieved November 6, 2013.

[compagno-1] ↑ ^a ^b ^c ^d ^e ^f ^g Compagno, LJV: Sharks of the World: An Annotated and Illustrated Catalog of Shark Species Known to Date . Food and Agricultural Organization, Rome 1984, ISBN 9251013845 , pp. 305-306.

[compagno_et_al.-2] A ^b ^c ^d Leonard Compagno, Marc Dando, Sarah Fowler: Sharks of the World. Princeton Field Guides, Princeton University Press, Princeton and Oxford 2005; Page 222. ISBN 978-0-691-12072-0 .

[mathews_and_ruiz-3] A ^b ^c Mathews, CP and MF Ruiz D .: Cephalurus cephalus, a Small Shark, Taken in the Northern Gulf of California, with a description . In: Copeia . 1974, No. 2, June 13, 1974, pp. 556-560.

[bigelow_and_schroeder-4] Bigelow, HB and WC Schroeder: Cephalurus, a New Genus of Scyliorhinid Shark with Redescription of the Genotype, Catulus cephalus Gilbert . In: Copeia . 1941, No. 2, July 8, 1941, pp. 73-76.

[5] Compagno, LJV : Alternative life-history styles of cartilaginous fishes in time and space . In: Environmental Biology of Fishes . 28, No. 3, 1990, pp. 3-75.

[6] Cortés, E .: Standardized diet compositions and trophic levels of sharks . In: ICES Journal of Marine Science . 56, 1999, pp. 707-717.

[7] Balart, EF, J. González-García and C. Villavicencio-Garayzar: Notes on the biology of Cephalurus cephalus and Parmaturus xaniurus (Chondrichthyes: Scyliorhinidae) from the west coast of Baja California Sur, México . In: Fishery Bulletin . 98, 2000, pp. 219-221. ( PDF )

[fishbase-8] Tadpole dogfish on Fishbase.org (English)

[9] Iglésiasa, SP, G. Lecointre and DY Sellos: Extensive paraphylies within sharks of the order Carcharhiniformes inferred from nuclear and mitochondrial genes . In: Molecular Phylogenetics and Evolution . 34, 2005, pp. 569-583.