White-edge Freshwater Whipray - Biology and Ecology

Biology and Ecology

Like the other freshwater and euryhaline members of its family, but unlike the specialized South American river stingrays of the family Potamotrygonidae, the white-edge freshwater whipray retains the ability to synthesize urea for osmoregulation and can survive in brackish water with a salinity of 20 ppt for at least two weeks. Its ampullae of Lorenzini are intermediate in size and structure between the large, complex ampullae of its marine relatives and the small, simple ampullae of potamotrygonid stingrays, which may be a consequence of varying salinities in its environment and demands that would place on electroreception. The white-edge freshwater whipray feeds mainly on small benthic organisms, including crustaceans, molluscs, and insect larvae. Reproduction is aplacental viviparous with the developing embryos sustained by maternally produced histotroph ("uterine milk"), as is the case in other stingrays. Newborns measure 10–12 cm (3.9–4.7 in) across; males and females mature sexually at 21–23 cm (8.3–9.1 in) and 25–26 cm (9.8–10 in) across respectively.