Giant freshwater stingray

Himantura polylepis

Himantura polylepis is a species of fish from the family of stingrays, which occurs in the Mekong and Chao Phraya, as well as in large rivers of Borneo and northern Australia. The species was described in 1852 and is one of the largest freshwater fish in the world. It is considered threatened because of their disjunct distribution area, the threat to their habitats and fishing by sport fishermen or as by-catch in some populations.

Features

Himantura polylepis is a huge skate with a wide but thin, oval body disc with sharp elongated snout. At the tail set, as with all members of the genus, no flaps on. The eye is very small. The body top is covered with placoid scales and uniformly brown or gray. The belly is white with a broad black border, which is interrupted more or less at the front. The tail is whip-like long and thin and wearing a single poisonous sting. The diameter of the disk of up to 2.40 meters, the total length of the tail can be up to five meters. Probably, the females are larger than males. The published maximum weight was 600 kilograms. Individuals in Australia are usually small and reach disc diameter of about one meter, and the total length of up to 270 centimeters.

Way of life

Himantura polylepis adheres to the sandy bottom of large rivers and feeds on invertebrates and fish. The species lives only in freshwater areas, and is viviparous.

System

The species was described as Himantura chaophraya 1990 but set in 2008 with comparisons by load and Manjaji - Matsumoto out that the type matches the type material of H. polylepis. Because of the wide distribution and the very different sizes of different populations, especially between animals from Thailand and those from Australia is thought that it could be of various types. The animals from Java are also different from the other populations and even the scattered populations occurring in Thailand could belong to different species. The animals from Australia have also been described as part of the work load and Manjaji - Matsumoto in 2008 as an independent species, Himantura dalyensis. Himantura dalyensis is therefore also valid species name for animals from New Guinea and Papua New Guinea. Further studies of the species complex seem to be urgently needed.

Swell

• Supap Monkolprasit, Tyson R. Roberts: Himantura chaophraya, a New Giant Freshwater Stingray from Thailand. In: Japanese Journal of Ichthyology. 37, No. 3, 1990, pp. 203-208 (PDF).
• Himantura polylepis on Fishbase.org (English)