Potamotrygon

Potamotrygon is a genus of freshwater stingrays in the family Potamotrygonidae. Endemic to South American rivers, they represent the only group of stingrays that live primarily in freshwater and occur in major basins such as the Amazon, Orinoco, Paraná, São Francisco, and Magdalena systems. They inhabit slow-moving to moderately flowing channels, floodplains, and backwaters with soft substrates.

Morphology and appearance vary among species, but Potamotrygon rays typically have a rounded to oval pectoral disc and a patterned dorsal surface that provides camouflage. The eyes are on the top of the body, while the mouth and gills are on the ventral side. The tail is slender and bears a venomous stinger. Adult size ranges by species, with some individuals reaching several tens of centimeters across.

Ecology and biology: Potamotrygon species are carnivorous, feeding on invertebrates, crustaceans, and small fish found on the river substrate. They are ovoviviparous or viviparous, giving birth to live young after a prolonged gestation, with embryos nourished by a placental connection similar to other rays.

Taxonomy and diversity: The genus comprises numerous species, many with overlapping ranges and similar patterns. Notable members include Potamotrygon motoro, Potamotrygon leopoldi, Potamotrygon falkneri, and Potamotrygon orbignyi, among others. Taxonomic relationships within Potamotrygon are subject to revision as new research emerges.

Human interactions and conservation: Potamotrygon rays are popular in the aquarium trade and require large, well-filtered systems with stable water conditions. In the wild, they play a role in river ecosystems, and several populations face threats from habitat degradation, pollution, and overcollection. Trade is regulated in some regions to protect wild populations.