Polydactylus
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| Lacepède , 1803 |
Polydactylus is the most species-rich genus of the threadlock with 20 species. In their area of distribution, the tropical and subtropical regions of all oceans, they are also important for fishing in many places. The type species is Polydactylus plumierii , but today this species is considered a synonym for Polydactylus virginicus .
description
This genus includes both slender and somewhat high-backed species. Their body length is between ten 10 to 20 centimeters to over a meter, next to Eleutheronema tetradactylum , the fingerfish , a member of the genus, is the largest threadfin fish with its maximum length of about two meters. Most species grow to be around 30 to 40 centimeters long. The basic color of the skin is usually silvery to grayish. The whole body, including the head, is covered by large, weakly toothed comb scales. At the front of the head there is a protruding "snout", under which the lower mouth is located, which is provided with several rows of fine teeth. Polydactylus species have large eyes, the diameter of which is always larger than the length of the snout. You have pronounced fat eyelids . The pectoral fins start well below the middle of the body. They consist of 12 to 18 soft rays . The four to nine long "antennae", which are characteristic of the family and give it its name, also belong to the pectoral fin. These thread-like appendages are nothing more than reshaped anterior pectoral fin rays, which are occupied with sensory cells and help the fish to feel the bottom for food. The paired pelvic fins are on the chest. The first and second dorsal fin are clearly separated, the former always consists of 8 spiny rays , the latter of a spine and 11 to 15 soft rays. The anal fin is opposite the second dorsal fin on the underside of the body and consists of three spine rays and 10 to 18 soft rays. The length of their attachment is always less than the length of the head. The species of the genus have a large, deeply forked caudal fin. There are five to eleven rows above the sideline and 8 to 16 rows below. Your spine consists of 14 vertebrae. Some species have a swim bladder , some don't.
Distribution, habitat and way of life
Polydactylus species are found in many tropical and subtropical areas of all oceans. The vast majority of species are native to the Indo-Pacific , only two East Pacific and four Atlantic species are known. They inhabit sandy and muddy sedimentary soils from very shallow water to a depth of 150 meters. Polydactylus macrophthalmus from Sumatra is the only species that lives in fresh water. On the bottom, they use their “feelers” to look for crabs and small fish. Their pronounced sense of touch is of particular importance to them, as they often live in murky water, where they cannot rely on their eyes when looking for food. Some species are known to be proterandric , which means that fry are initially male and then become females as they grow.
use
The genus Polydactylus is one of the most important for fishing in the tropics, especially in Asia. Some species are considered good edible fish . Isinglass is obtained from parts of the body of some species , such as Polydactylus tetradactylus . Some species, for example Polydactylus quadrifilis and Polydactylus macrochir , are popular among sport fishermen . Polydactylus sexifilis is aquacultured in Hawaii .
Systematics
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The genus comprises 20 species, making it the most species-rich within the threadfin family.
- Polydactylus approximans (Lay & Bennett, 1839) .
- Polydactylus bifurcus Motomura, Kimura & Iwatsuki, 2001 .
- Polydactylus longipes Motomura, Okamoto & Iwatsuki, 2001 .
- Polydactylus macrochir ( Günther , 1867) .
- Polydactylus macrophthalmus ( Bleeker , 1858) .
- Polydactylus malagasyensis Motomura & Iwatsuki, 2001 .
- Polydactylus microstomus ( Bleeker , 1851) .
- Polydactylus mullani (Hora, 1926) .
- Polydactylus multiradiatus ( Günther , 1860) .
- Polydactylus nigripinnis Munro , 1964 .
- Polydactylus octonemus ( Girard , 1858) .
- Polydactylus oligodon (Günther, 1860) .
- Polydactylus opercularis Seale & Bean, 1907 .
- Polydactylus persicus Motomura & Iwatsuki, 2001 .
- Polydactylus plebeius (Broussonet, 1782) .
- Fingerfish ( Polydactylus quadrifilis ) ( Cuvier , 1829) .
- Polydactylus sexfilis ( Valenciennes , 1831) .
- Polydactylus sextarius ( Bloch & Schneider , 1801) .
- Polydactylus siamensis Motomura, Iwatsuki & Yoshino, 2001 .
- Polydactylus virginicus ( Linnaeus , 1758) .
swell
- Roland J. McKay: Threadfins of the world (Family Polynemidae). An annotated and illustrated catalog of polynemid species known to date. FAO Species Catalog for Fishery Purposes. No. 3rd FAO Rome 2004. ( PDF )
- Dr. Dr. HC Bernhard Grzimek : “ Grzimek's animal life . The modern encyclopedia of the entire animal kingdom. ”1970 Kindler Verlag AG, Zurich
- Polydactylus on WoRMS
Individual evidence
- ↑ a b c d e Roland J. McKay: An annotated and illustrated catalog of polynemid species known to date. FAO Species Catalog for Fishery Purposes. No. 3rd FAO Rome 2004. ( PDF )
- ↑ Dr. Dr. HC Bernhard Grzimek : “ Grzimek's animal life . The modern encyclopedia of the entire animal kingdom. ”1970 Kindler Verlag AG, Zurich
