Japanese pylonos [1] [2] , or Japanese shark-pilonos [3] ( lat. Pristiophorus japonicus ) is a species of cartilaginous fish of the genus pylonos of the family of pilonos sharks . These sharks live in the northwestern Pacific Ocean at a depth of up to 500 m. The maximum recorded length is 136 cm. The snout is elongated, forming a sawtooth rostrum dotted with lateral teeth. There are antennae on the rostrum. These sharks breed by egg-laying . The diet consists of small bottom animals. Of little interest for commercial fisheries [4] .
| Japanese pilonos |
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| No rank : | Bilateral symmetrical |
| Squad: | Pyliform ( Pristiophoriformes Compagno , 1973 ) |
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Pristiophorus japonicus GΓΌnther , 1870 |
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Not enough data IUCN Data Deficient : 161634 |
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Japanese pilonos live in the northwestern Pacific Ocean and off the coast of Korea, Japan, China and, possibly, the Philippines [4] . These sharks are found at the bottom on the continental shelf and in the upper part of the continental slope at a depth of up to 500 m [5] , and according to other sources up to 800 m [6] .
In Japanese pylons, the body is elongated, slightly flattened, but not flattened like a ray. The head is also slightly flattened, but not stretched laterally. Snout elongated and flattened, elongated in the form of a sawtooth rostrum with lateral teeth. Its length is 26-29% of the body length. The antennae located on the rostrum are 1.1-1.2 times closer to the mouth than to the tip of the snout. On each side of the rostrum in front of the antennae there are 15β26 large teeth and 9β17 behind the antennae. The edges of large teeth are smooth. The distance from the antennae to the nostrils is almost equal to the distance between the nostrils and 1β4 gill slits. The distance from the mouth to the nostrils is 1.1-1.2 times the distance between the nostrils. There are 34β58 teeth on the upper jaw [4] .
The two dorsal fins lack spines at the base. Anal fin missing. The base of the first dorsal fin is located at the level of the space between the pectoral and ventral fins. The pectoral fins are rather large, but not pterygoid. The ventral fins are small. The mouth is located before the eyes. There are nasal grooves that do not connect to the mouth. Labial grooves are short. Oval rather large eyes are elongated horizontally. The third eyelid is absent. 5 pairs of gill slits. Behind the eyes there are large splashes . Caudal fin asymmetrical, upper lobe elongated, lower lobe absent. In large specimens, dorsal and pectoral fins are covered with placoid scales. The body is covered with large, pointed, placoid scales . The maximum recorded length is 136 cm [4] , according to other sources 153 cm [6] .
Japanese pilonos breed by egg-laying. In litter up to 12 newborns with a length of about 30 cm [6] [4] . Probably, the rostral large teeth erupt shortly before birth, but in order not to cause harm to the mother, they remain pressed to the rostrum, and the small ones erupt between the large ones after birth, then the large teeth straighten out as well [4] . Males and females reach puberty with a length of 80-100 cm and 100 cm, respectively [6] .
The diet of Japanese pilonos consists of small bottom animals. The long sensitive rostrum has a lateral line capable of detecting vibration and is equipped with electroreceptors . A flat head and snout, a large occipital condyle and specialized cervical vertebrae allow pilonos sharks to use the rostrum as a powerful weapon to dig through the ground and kill the victim. However, such behavior was not recorded firsthand, because, unlike sawfly stingrays , these sharks cannot be kept in captivity. Very short jaws and elongated oral and gill cavities suggest that Japanese pilonos are capable of suddenly sucking a victim [4] .
Sharks of this species make vertical migrations associated with water temperature, and move from shallow coastal waters to the upper part of the continental slope. In shallow water off the coast of the Izu Peninsula, they are found only in early spring, when the water has not yet warmed up [6] .
Japanese pylons are not dangerous for humans, but care should be taken when handling them, since sharp rostral teeth can seriously injure [4] . These sharks are caught in by-catch in the target fishery using gillnets, trawls and bottom tiers. Pylons are often entangled in networks by their rostrum. In Japan, their meat is highly regarded, probably made from kamaboko . [4] There is insufficient data to evaluate the conservation status of the species by the International Union for Conservation of Nature . [6] .
- β Lindberg, G.W. , Gerd, A.S. , Russ, T.S. Dictionary of the names of marine commercial fish of the world fauna. - Leningrad: Nauka, 1980 .-- S. 49. - 562 p.
- β Reshetnikov Yu.S. , Kotlyar A.N. , Russ T.S. , Shatunovsky M.I. The Bilingual Dictionary of Animal Names. Fish. Latin, Russian, English, German, French. / edited by Acad. V. E. Sokolova . - M .: Rus. Yaz., 1989 .-- P. 38 .-- 12,500 copies. - ISBN 5-200-00237-0 .
- β Animal life. Volume 4. Lancelet. Cyclostomes. Cartilaginous fish. Bone fish / ed. T. S. Rassa , ch. ed. V. E. Sokolov . - 2nd ed. - M.: Education, 1983 .-- S. 43. - 575 p.
- β 1 2 3 4 5 6 7 8 9 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 Annotated and Illustrated Catalog of Shark Species Known to Date. - P. 134β136. - ISBN 92-5-101384-5 .
- β Pristiophorus japonicus (neopr.) . Fishbase Date of treatment March 4, 2014.
- β 1 2 3 4 5 6 Japanese pilonos (English) . The IUCN Red List of Threatened Species . Date of treatment March 4, 2014.
