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The Indian threadfin (''Leptomelanosoma indicum'') is a species of marine
ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...
from the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Polynemidae, the
threadfin Threadfins are silvery grey fish of the family Polynemidae, taxonomically considered a type of flatfish. Found in tropical to subtropical waters throughout the world, the threadfin family contains eight genera and about 40 species. An unrelated s ...
s. It is a coastal species from south-east Asia which has been recorded in Papua New Guinea.


Description

The Indian threadfin is a large species with an elongated head and body. Its eye is roughly the same size as the length of its snout. The joint of the jaws is to the rear of the eyelid. It has two separated
dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
s, the first dorsal fin contains 8 spines while the second dorsal fin has a single spine and 12 or 13 soft rays. The
anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...
has 3 spines and 10 or 11 soft rays. The base of the anal-fin is shorter than that of the second dorsal-fin. The
pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...
has 12 to 14rays and has a length equivalent to 19 to 22% of the
standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...
, its tip not reaching to the tip of the
pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...
. The pectoral fin is situated well below the body's midline. There are five pectoral filaments, the first one being the shortest and does not extend to the pelvic fin while the fifth filament is the longest with a length equivalent 28 to 45% of standard length and extending well beyond the posterior tip of the pelvic fin. The
caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...
is deeply forked with the upper and lower lobes being extremely long and filamentous. It has 69 to 72 pored scales in its simple
lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...
which extends from the upper end of gill opening to upper end of lower lobe of the caudal-fin lobe. The head and upper flanks are tinted slightly blackish brown, darkening on the lower flanks. The snout and abdomen are blackish. The membranes of first and second dorsal fins and caudal fin are blackish with their outer portions being black. The membrane of the pectoral fin is deep black with the base of the filaments being dusky yellow, darkening to the rear. The pelvic fin is also dusky yellow at its base and dirty white on its other parts. This species can attain a length of but most specimens will be around .


Distribution

The Indian threadfin has been confirmed as occurring in the coastal waters of southern Asia from Pakistan to
Borneo Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...
. In Papua New Guinea there is a single record of a
specimen Specimen may refer to: Science and technology * Sample (material), a limited quantity of something which is intended to be similar to and represent a larger amount * Biological specimen or biospecimen, an organic specimen held by a biorepository f ...
taken in
Kerema Bay Kerema Bay is a bay in Papua New Guinea. It is located in the Gulf Province next to the capital city Kerema, 230 km northwest of Port Moresby. The climate in the region is Tropical rainforest climate, tropical. References

Bays of Papua ...
in the
Gulf of Papua The Gulf of Papua is located in the southern coast region of New Guinea. It has a total surface area of . Geography Some of New Guinea's largest rivers, such as the Fly River, Turama River, Kikori River, Purari River, and Wawoi River flow ...
. Records from Africa are unconfirmed and not now regarded to be of this species.


Habitat and ecology

The Indian threadfin is found over shallow muddy and sandy substrates on the continental shelf, especially in the vicinity of estuaries and it is known to enter rivers. It is carnivorous and the largest part of its diet is small
benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...
crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...
s, such as prawns and crabs, and small fishes. The amount of fishes taken increases as the fishes grow larger. It has been taken from as deep as but rarely below . In a sample taken off India 40% of the fish caught were hermaphrodites, 19.3% were males and 41% were females. They spawn in two main periods, April to June and October to November, with the main breeding season being April to June. However, in southern India spawning was in October and November.


Fisheries

The Indian threadfin is one of the most important quarries for fisheries of a number of Asian nations< They are caught with gill nets, trawls, handlines and beach seines. The flesh is used fresh or preserved by freezing, drying and smoking and is prepared by baking, steaming, frying or broiling.


Species description and taxonomy

This species was first formally described by as ''Polynemus indicum'' in 1804 by the Irish naturalist George Shaw from a drawing by Russell and he gave the location of the
type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...
as
Vizagapatam Visakhapatnam (; formerly known as Vizagapatam, and also referred to as Vizag, Visakha, and Waltair) is the largest and most populous metropolitan city in the Indian state of Andhra Pradesh. It is between the Eastern Ghats and the coast of t ...
. It was reclassified into the
monospecific In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...
genus ''Leptomelanosoma'' in 2001.


References

{{Taxonbar, from=Q2452692 Polynemidae Taxa named by George Shaw Fish described in 1804