Mekong Freshwater Stingray

Fish World | Mekong Freshwater Stingray | Mekong Freshwater Stingray, Dasyatis laosensis, is a species of skate in Dasyatidae family, restricted to the Mekong and Chao Phraya Rivers in Laos and Thailand. Measuring up to 62 cm (24 inches) in diameter, this range is a hard oval pectoral fins, a tail with two-ply top and bottom of the fin, and a middle row of spine-like dermal denticles. A characteristic feature of this species is its bright orange underside. Mekong Freshwater Stingray prey on invertebrates and is aplacental viviparous. It has been assessed as endangered by the International Union for Conservation of Nature (IUCN), it is threatened by overfishing and habitat degradation.

Mekong Freshwater Stingray was first recognized as a new species by Yasuhiko Taki, who included it as "Dasyatis sp." 1968 in its list of fish of the Mekong in Laos. Taki specimens were then lost, and this radius was not officially described until 1987 by Tyson Roberts and Jaranthada Karnasuta, in the journal Environmental Biology of Fishes. The type specimen is an immature male of 23 cm (9.1 inches) in diameter, caught in the Mekong River in Chiang Rai province, Thailand. 1999 A phylogenetic analysis based on sequences of cytochrome b, found that Mekong Freshwater Stingray is closely related to an undescribed species Dasyatis the Gulf of Thailand.

A resident of the exclusive major freshwater rivers, Mekong Freshwater Stingray was recorded in sand habitats in the Mekong River in Laos-Thailand border, and the Chao Phraya River near the Chai Nat central Thailand. The populations of these two rivers are likely isolated from each other.

Disk pectoral fin of Mekong Freshwater Stingray is oval and slightly longer than wide. The tip of the snout protrudes slightly past the disk. The eyes are small and followed by a slightly larger stigma. There are from 28 to 38 rows of upper and lower teeth from 33 to 41 rows of teeth, the teeth of juveniles and females are dull, while adult males showed up with a central keel. The jaws of adult males also become highly curved. A row of five taste buds are on the floor of the mouth, with the outermost pair smaller than others. The five pairs of gill slits are short. The pelvic fins are longer than wide and triangular with rounded corners. The whip like tail is over twice the width of the disc and bears a (rarely 2) spines tingling on the top surface. Both dorsal and ventral folds are behind the spine, with the ventral 2.5 to 3 times longer than the upper fold.
A single row of spines similar to dermal denticles along the midline of the back and tail, with the largest found at the base of the tail. The number of center line extended denticles increases with age. There is also a narrow band of minute denticles or sharp granular on the back, which are confined by a pair of parallel lines drawn back from the stigma. The upper surface of the disc and tail are brown, the tail folds much darker. The underside is pale with large, irregular yellow-orange spots and a large red-orange band around the margin of the disc. Bright orange color also characterizes the ventral red Stingray (D. akajei) Pacific Northwest, the two species have similar meristic some numbers, but differ in the shape of the disc, spines, and dorsal coloration. The maximum width of the disks known to the Mekong freshwater stingray is 62 cm (24 in.), it can reach a weight would have 30 kg (66 lb).
The diet of Mekong Freshwater Stingray consists of invertebrates from the river bed. Like other rays, it is aplacental viviparous with litter sizes as small as a puppy can

Mekong Freshwater Stingray is subjected to intensive fishing for large fish bone. It is taken involuntarily, usually in seine nets or hook and line, and sold fresh for human consumption; fishermen typically break the spine tail before bringing it to market. However, a greater threat to the survival of this species is habitat degradation widespread within its limited scope, the dam construction, agricultural runoff and industrial pollution. Finally, the small juveniles can be collected for the aquarium trade. Because of these pressures, the International Union for Conservation of Nature (IUCN) assessed the species as endangered. The Thai government has launched a program of captive breeding of this species of fresh water and other lines in the 1990s in Chai Nat, but the program has since been put on hold.

Scientific classification

Kingdom: Animalia 
Phylum: Chordata
Class: Chondrichthyes
Order: Myliobatiformes
Family: Dasyatidae 
Genus: Dasyatis 
Species: D. laosensis