The big-toothed shark [1] ( Latin Isistius plutodus ) is a rare species of cartilaginous fish from the genus of luminous sharks of the Dalatian family. This is a small deep-sea shark, known for its bright glow and the ability to bite pieces of meat from much larger fish and cetaceans [2] . These sharks are found in isolated places in the Atlantic and Pacific oceans at a depth of up to 6440 m [3] . Outwardly, they look like Brazilian glowing sharks - they have a cigar-shaped body, a short and blunt snout, large eyes, 2 tiny dorsal fins. The main difference is that their lower teeth are much larger. The dark collar around the throat and gill area is absent in most individuals. They feed on bony fish and bite off pieces of flesh from the bodies of large fish and marine mammals. Bite marks are bigger than bites from luminous Brazilian sharks. Reproduced by egg production . As by- catch they fall into commercial trawls and longlines.
Big Tooth Shark |
Scientific classification |
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No rank : | Bilateral symmetric |
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International Scientific Name |
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Isistius plutodus Garrick & |
Area |
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Security status |
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Least concernIUCN 3.1 Least Concern : 60212 |
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Content
TaxonomyFor the first time, the species was scientifically described in 1964 by and in the scientific journal [4] . The holotype is a 41.5 cm long female caught on October 27, 1960 off the coast of Alabama in the Mississippi Delta at 28 ° 58 's. sh. and 88 ° 18 'h. at a depth of 813–996 m [5] . The specific name comes from the word πλοῦτος - “wealth” [6] .
Distribution and habitatIsistius plutodus are much less common in Brazilian luminous sharks. So far, only 10 individuals have been recorded in the western part of the Atlantic Ocean off the coast of Alabama ( USA ), Bahia ( Brazil ), in the eastern Atlantic off the coast of Western Sahara and in the Pacific Ocean in the waters of Okinawa ( Japan ) and New South Wales ( Australia ) . All sharks were caught in the epipelagic zone at a depth of 60 to 200 m at the bottom, on the continental shelf , on the continental slope or in oceanic troughs , which descend to 6440 m [7] [3] .
DescriptionThe maximum size of sharks of this species is about 42 cm [2] . They have an elongated cigar-shaped body with a short blunt snout and large oval eyes, the position of which provides these sharks with binocular vision . Behind the eyes there are wide sprayers . The small nostrils are framed in front with short patches of skin. The mouth forms an almost transverse line. There are folds in the corners of the mouth. Lips are thick, adapted for suction [4] . The teeth are larger and more powerful than those of the Brazilian luminous sharks. The number of them is also greater: there are 29 on the upper jaw, and 19 on the lower dentition [2] . The upper teeth are small, narrow, with smooth edges, in the center they are located vertically, and closer to the edges of the jaw tilted [4] . Lower teeth are massive. Isistius plutodus has the maximum ratio of the size of the lower teeth and the length of the body among the living sharks [8] . They have a triangular shape, and the edges are covered with tiny notches. Lower teeth interlocked with rectangular bases. There are 5 pairs of tiny gill slits [4] .
Two small rounded dorsal fins lack spines and are strongly shifted back to the last third of the body. The base of the first dorsal fin is located in front of the base of the ventral fins. The second dorsal fin is 1/3 of the height of the first one. Short pectoral fins are rounded, they are located behind the fifth gill slit. The tail fin is short and asymmetrical: the upper lobe is almost 2 times longer than the lower one. At the edge of the upper lobe there is a noticeable ventral notch [2] . There is no anal fin. Body color is uniform dark brown; the ventral part of the body is covered with luminous photophores, the dark “collar” around the throat and gill slits of most sharks is absent [4] .
BiologyIn the large-toothed luminous sharks, the small dorsal and tail fins are less active compared to the Brazilian luminous sharks and swim less well. They have a huge, fat-filled liver, allowing you to maintain neutral buoyancy in the water column without much effort. In contrast to the Brazilian luminous sharks, Isistius plutodus have binocular vision and can target the victim with greater accuracy [2] . About the biology of this species is virtually unknown. Probably, the sharks of this species reproduce by egg production [9] .
Being Isistius plutodus , however, they hunt small prey, for example, bony fish. While theoretically the Brazilian glowing sharks bite into the body of the victim and take pieces of flesh out of it, spinning around their axis, inflicting round wounds with spiral-shaped internal grooves from the lower teeth, Isistius plutodus bite the meat in one bite, leaving more elongated (2 times longer than mouth) oval wounds with parallel teeth marks [10] . They attack large bony and cartilaginous fish and marine mammals [7] [2] [11] . In one study, it was found that 80% of the characteristic marks on the body of cetaceans off the coast of Bahia were signs of Isistius plutodus bites. Most often, sharks bit the whales by the sides, then the head and the belly followed the frequency of the lesions. In at least 3 cases, as a result of shark attacks, dolphins jumped ashore and died [11] . In two other cases, immature subtropical fur seals were also found dead on the beach with fresh marks from the teeth of Isistius plutodus on the body.
Human interactionIsistius plutodus is of no interest to commercial fisheries. Sometimes they are caught in trawls and longlines as by-catch. The International Union for Conservation of Nature has given this species the status of “Causes the least concern” [7] .
Notes- ↑ Reshetnikov Yu. S. , Kotlyar A. N. , Russ T. S. , Shatunovsky M. I. Pyatiazychny dictionary of animal names. Fish. Latin, Russian, English, German, French. / edited by Acad. V.E. Sokolova . - M .: Rus. laz., 1989. - p. 36. - 12 500 copies. - ISBN 5-200-00237-0 .
- ↑ 1 2 3 4 5 6 Compagno, Leonard JV 1. Hexanchiformes to Lamniformes // FAO species catalog. - Rome: Food and Agricultural Organization of the United Nations, 1984. - Vol. 4. Sharks of the World: An Antaled and Illustrated Catalog of Shark Species Known to Date. - P. 95-96. - ISBN 92-5-101384-5 .
- 1 2 Kiraly SJ, Moore JA and Jasinski PH Deepwater / Maritime Area Exclusive Economic Zone // Mar. Fish. Rev .. - 2003. - Vol. 65, № 4 . - P. 9.
- 2 1 2 3 4 5 Garrick JAF, Springer S. Isistius plutodus , a New Squaloid Shark from the Gulf of Mexico // Copeia. - 1964. - № 4 . - P. 678-682. - DOI : 10.2307 / 1441443 .
- ↑ Isistius plutodus (Neopr.) . Shark-References.com. The appeal date is April 14, 2013. Archived April 21, 2013.
- ↑ Large ancient Greek dictionary (Neopr.) . The appeal date is February 9, 2013. Archived February 12, 2013.
- ↑ 1 2 3 Kyne PM, Gerber L., Sherrill-Mix SA (2006). Isistius plutodus. IUCN Red List of Threatened Species. Version 2010.4. International Union for Conservation of Nature.
- ↑ McGrouther, M. Largetooth Cookiecutter Shark, Isistius plutodus Garrick & Springer, 1964 (Neopr.) . Australian Museum ((June 19, 2009)). The appeal date is April 14, 2013. Archived April 21, 2013.
- ↑ Larva shark glowing (English) in FishBase database.
- ↑ Pérez-Zayas JJ, Mignucci-Giannoni AA, Toyos-González GM, Rosario-Delestre RJ, Williams EH Jr. (2002). Incidental predation by a largetooth cookiecutter shark on a cuvier's beaked whale in Puerto Rico. Aquatic Mammals 28 (3): 308-311.
- ↑ 1 2 Souto LRA, Abrão-Oliveira JG, Nunes JACC, Maia-Nogueira R., Sampaio CLS Analysis of cookie cutter shark Isistius spp. (Squaliformes; Dalatiidae) bites in cetaceans (Mammalia; Cetacea) on the Bahia coast, northeastern Brazil // Biotemas. - (March 2007). - Vol. 20, № 1 . - P. 19-25.