Angler's File: River stingray(Potamotrygonidae)

Tuesday, 18 December 2012

River stingray(Potamotrygonidae)

River stingray(Potamotrygonidae)

River stingrays

Ocellate river stingray, Potamotrygon motoro
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Order:	Myliobatiformes
Family:	Potamotrygonidae Garman, 1877
Genera
Heliotrygon Paratrygon Plesiotrygon Potamotrygon

River stingrays are Neotropical freshwater fishes of the Potamotrygonidae family (order Myliobatiformes).

They are native to northern, central and eastern South America, living in rivers that drain into the Caribbean, and into the Atlantic as far south as the Río de la Plata in Argentina. Generally, each species is native to a single river basin, and the greatest species richness can be found in the Amazon.

River stingrays are almost circular in shape, and range in size from Potamotrygon schuhmacheri, which reaches 25 centimetres (9.8 in) in diameter, to the short-tailed river stingray, P. brachyura, which grows up to 1.5 metres (4.9 ft) in diameter. The upper surface is covered with denticles (sharp tooth-like scales). Most species are brownish or greyish and often have distinctive spotted or mottled patterns, but a few species are largely blackish with contrasting white spots.

They have a venomous caudal sting, and are one of the most feared freshwater fishes in the Neotropical region, sometimes more feared than piranhas and electric eels. However, they are not dangerous unless stepped on or otherwise threatened.

River stingrays are the only family of batoids completely restricted to fresh water habitats; while there are true freshwater species in the family Dasyatidae, for example Himantura chaophraya, the majority of species in this family are saltwater fish.