| Polydactylus sextarius | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Perciformes |
| Family: | Polynemidae |
| Genus: | Polydactylus |
| Species: | P. sextarius |
| Binomial name | |
| Polydactylus sextarius | |
| Synonyms [1] | |
| |
Polydactylus sextarius, the blackspot threadfin, is a species of marine ray-finned fish, a threadfin from the family Polynemidae which is native to the western Pacific and eastern Indian Oceans.
Polydactylus sextarius is a small- to medium-sized threadfin which attains a maximum total length of 30 centimetres (12 in) but 20 centimetres (7.9 in) is more common. [1] It has a pointed snout with the dorsal profile of the head being almost straight. There are two separate dorsal fins, the first with 8 similar spines and the second dorsal fin has a single spine and 12 or 13 soft rays. The anal fin has 3 spines and 11 to 13 soft rays, with the anal fin base being roughly the same length as the base of the second dorsal fin. The pectoral fin contains 13 to 15 rays most if which are solid lacking branches, with the exception of the highest 1 or 2, the tip of the pectoral fin does not extend as far as the tip of the pelvic fin. There are six pectoral filaments with the first being the shortest and the sixth being the longest, at more than a quarter of the standard length but not reaching to the tip of the pectoral fin. The caudal fin is deeply forked, with its long lobes lacking filaments, the length of both lobes reaching a maximum of 41% of standard length. The simple lateral line has 45 to 51 pored scales and extends from the upper end of the gill slit to the upper end of lower caudal fin lobe. The head and upper flanks are dark with a silver tinge paler on the lower flanks. It has a semi transparent snout. Both dorsal fins and the caudal fin are translucent with a sooty rear margin. The anal fin is blackish with a whitish tip. The pectoral fin membrane is white with scattered black spots. The pectoral filaments are whitish. The front of the pelvic fin is yellowish white, paler towards the rear, There is a large black spot on lateral line just behind the upper part of the gill opening. [2]
Polydactylus sextarius is found in the Eastern Indian Ocean and Western Pacific. Its range extends from southwestern India to Papua New Guinea, north to Japan. It is rare in the Philippines, eastern Indonesia, and Papua New Guinea. [1]
Polydactylus sextarius is found where there are sandy and muddy bottoms on the continental shelf [1] and it appears to favour depths of 16 to 73 metres (52 to 240 ft). This carnivorous species has its diet dominated by shrimps of less than 20 millimetres (0.79 in) length and amphipods but it has also been recorded feeding on crabs, mysids, fishes and polychaetes. Sampling of the population in the Bay of Bengal off India found that a large proportion of the fish are hermaphrodites and that these fell within the range of standard length of 50 to 149 millimetres (2.0 to 5.9 in), with a smaller proportion of females with standard lengths of between 100 and 105 millimetres (3.9 and 4.1 in). The hermaphrodites with comparatively large testes were counted as mature males and these measured 90 to 134 millimetres (3.5 to 5.3 in) standard length) while the fish with granulated ova of 0.3 to 0.5 millimetres (0.012 to 0.020 in) diameter were considered to be mature females and these fell within the standard length range of 105 to 149 millimetres (4.1 to 5.9 in). The species undergoes a protandrous sex change starting as juveniles, becoming hermaphrodites and ending as females progression. They first reach sexual maturity as hermaphrodites which function as males and there is no evidence which suggests that females develop directly from juveniles. [2]
Polydactyus sextarius is an important species for commercial fisheries in the Bay of Bengal and off Thailand where it is caught using trawls. [2]
Polydactylus sextarius was first formally described as Polynemus sextarius in 1801 by Marcus Elieser Bloch and John Gottlob Schneider with the type locality given as Tranquebar in India. [3]
Threadfins are silvery grey perciform fish of the family Polynemidae. Found in tropical to subtropical waters throughout the world, the threadfin family contains eight genera and about 40 species. An unrelated species sometimes known by the name threadfin, Alectis indicus, is properly the Indian threadfish.
The Atlantic threadfin is a species of ray-finned fish a threadfin from the family Polynemidae which is native to subtropical and temperate waters of the western Atlantic Ocean and the Gulf of Mexico.
Eleutheronema tetradactylum, the fourfinger threadfin, is a species of marine ray-finned fish, a threadfin from the family Polynemidae which occurs in the Indian and western Pacific Ocean.
Nemipterus virgatus, the golden threadfin bream or yellowlipped threadfin bream, is a species of marine ray-finned fish belonging to the family Nemipteridae, the threadfin breams. This species is found in the Western Pacific Ocean.
The giant African threadfin is a species of ray-finned fish from the threadfin family Polynemidae. It is found in the eastern Atlantic Ocean off the west coast of Africa.
Polydactylus sexfilis, the six-finger threadfin or yellowthread threadfin, is a species of marine ray-finned fish, a threadfin from the family Polynemidae which is found in the Indian and Pacific Oceans.
The king threadfin, also known as the blind salmon, blink tassel-fish, burnett salmon, gold threadfin, king salmon, kingfish, Sheridan threadfin, triped tassel fish, or threadfin salmon, is a species of marine ray-finned fish, a threadfin from the family Polynemidae which is found in southern New Guinea and northern Australia.
The Indian threadfin is a species of marine ray-finned fish from the family Polynemidae, the threadfins. It is a coastal species from south-east Asia which has been recorded in Papua New Guinea.
Polynemus multifilis, the elegant paradise fish is a species of ray-finned fish, a threadfin from the family Polynemidae which is found in rivers in southeast Asia.
Polynemus aquilonaris, commonly known as the northern paradise fish, is a fish of the threadfin family Polynemidae. It is native to the large rivers of mainland Southeast Asia.
Polydactylus plebeius, the striped threadfin, also known as the common threadfin, Northern threadfin or puttynose, is a species of marine fish native to the Indo-Pacific.
Nemipterus peronii, the notchedfin threadfin bream, notchedfin butterfly breamrosy threadfin bream or Peron's threadfin bream, is a species of marine ray-finned fish belonging to family Nemipteridae, the threadfin breams. This species occurs in the Indo-West Pacific region.
Nemipterus japonicus, the Japanese threadfin bream, is a species of marine ray-finned fish belonging to the family Nemipteridae, the threadfin and whiptail breams. This species is found in the Indo Pacific region and is an important food fish.
Nemipterus isacanthus, the teardrop threadfin bream or twinlined threadfin bream, is a species of marine ray-finned fish belonging to the family Nemipteridae, the threadfin and whiptail breams. This fish is found in the western Pacific Ocean.
The yellowbelly threadfin bream is a species of marine ray-finned fish belonging to the family Nemipteridae, the threadfin and whiptail breams. This fish is found in the western Pacific Ocean.
The dwarf paradise fish, also known as the streamer threadfin or streamered tasselfish, is a species of ray-finned fish from a family Polynemidae, the threadfins. It is the only species in the genus Parapolynemus and it is found in Australia and New Guinea.
The paradise threadfin is a species of catadromous ray-finned fish, a threadfin from the family Polynemidae which is found in south and southeast Asia in freshwater rivers where it is a valued food fish.
Filimanus is a genus of marine ray-finned fishes, threadfins from the family Polynemidae.
The royal threadfin is a species of ray-finned fish, a threadfin from the family Polynemidae, the threadfins. It is found in the eastern Atlantic Ocean along the western coast of Africa.
The doublewhip threadfin bream is a species of marine ray-finned fish belonging to the family Nemipteridae, the threadfin breams. This species is found in the Indo-West Pacific region.