Mekong freshwater stingray – Wikipedia

Species of cartilaginous pisces

The Mekong freshwater stingray, Hemitrygon laosensis, is a species of stingray in the family Dasyatidae, restricted to the Mekong and Chao Phraya Rivers in Laos and Thailand ; the occurrence in Chao Phraya is considered an initiation. [ 1 ] Measuring up to 62 centimeter ( 24 in ) across, this irradiate has an ellipse pectoral fin disk, a tail with both upper berth and lower fin folds, and a midplane row of spine-like dermal denticles. A characteristic feature of this species is its bright orange bottom. The Mekong fresh water stingray preys on invertebrates and is aplacental viviparous. It has been assessed as Endangered by the International Union for Conservation of Nature ( IUCN ), as it is threatened by overfishing and habitat degradation .

Taxonomy and phylogeny [edit ]

The Mekong fresh water stingray was first recognized as a new species by Yasuhiko Taki, who included it as “ Dasyatis sp. ” in his 1968 number of Mekong River fishes from Laos. Taki ‘s specimens were subsequently lost, and this beam was not formally described until 1987, by Tyson Roberts and Jaranthada Karnasuta, in the scientific daybook Environmental Biology of Fishes. The type specimen is an immature male 23 curium ( 9.1 in ) across, catch from the Mekong in Chiang Rai Province, Thailand. [ 2 ] A 1999 phylogenetic analysis, based on cytochrome b sequences, found that the Mekong fresh water stingray is closely related to an undescribed dasyatid species from the Gulf of Thailand. [ 3 ]

distribution and habitat [edit ]

An single inhabitant of large, fresh water rivers, the Mekong fresh water stingray has entirely been recorded from arenaceous habitats in the Mekong River along the Laos-Thailand surround, and in the Chao Phraya River near Chai Nat in cardinal Thailand. The populations of these two rivers are probably isolated from each other. [ 2 ] [ 4 ]

description [edit ]

The pectoral fin magnetic disk of the Mekong fresh water stingray is ellipse in supreme headquarters allied powers europe and slightly longer than wide-eyed. The tip of the snout protrudes slenderly past the magnetic disk. The eyes are humble and followed by slightly larger spiracles. There are 28–38 upper tooth rows and 33–41 lower tooth rows ; the tooth of juveniles and females are numb, while those of adult males are pointed with a central keel. The chew the fat of pornographic males besides become powerfully curved. A row of 5 papillae lie across the floor of the mouth, with the outermost couple smaller than the others. The five pairs of gill slits are short. The pelvic fins are longer than wide and triangular with round corners. The whip-like tail is no longer than twice the disk width and bears 1 ( rarely 2 ) stinging spines on the upper surface. Both abaxial and adaxial fin folds are found behind the spine, with the ventral fold 2.5–3 times longer than the upper fold. [ 2 ]

Read more: Max (bunny)

A individual row of thorn-like cutaneous denticles runs along the midplane of the back and tail ; with the largest find at the base of the tail. The issue of elaborate midplane denticles increases with historic period. There is besides a constrict ring of infinitesimal farinaceous or pointed denticles on the back, which are confined by a pair of parallel lines drawn backward from the spiracles. The upper coat of the magnetic disk and tail are plain brown university, with the buttocks folds much dark. The bottom is pale with large, guerrilla orange-yellow patches and a wide orange-red band around the magnetic disk margin. Bright orange ventral color besides characterizes the loss stingray ( H. akajei ) of the northwestern Pacific ; the two species have some like meristic counts, but differ in magnetic disk supreme headquarters allied powers europe, denticles, and dorsal coloration. [ 2 ] The maximum know magnetic disk width of the Mekong fresh water stingray is 62 curium ( 24 in ) ; [ 5 ] it can reportedly reach a weight of 30 kg ( 66 pound ). [ 2 ]

Biology and ecology [edit ]

The diet of the Mekong fresh water stingray consists of invertebrates from the river bed. [ 4 ] Like other stingrays, it is aplacental viviparous with litter sizes possibly ampere modest as one puppy. [ 1 ]

human interactions [edit ]

The Mekong fresh water stingray is subject to intensifier fishing aimed at large bony fishes. [ 2 ] It is caught unintentionally, typically in seine nets or on hook-and-line, and sold fresh for human consumption ; fishermen typically break off the fag end spur before bringing it to market. [ 4 ] however, a greater terror to the survival of this species is widespread habitat abasement within its limited scope, from dam construction, agricultural runoff, and industrial contamination. finally, the modest juveniles may be collected for the aquarium deal. Because of these pressures, the International Union for Conservation of Nature ( IUCN ) has assessed this species as Endangered. The thai government initiated a captive education program for this and other fresh water stingray species in the 1990s at Chai Nat, but the course of study has since been placed on delay. [ 1 ]

References [edit ]

Leave a Comment