Parnaíba River Stingray.
A medium-sized freshwater stingray with an oval disc that is longer than wide. Small lobe visible on tip of snout. Head relatively broad. Eyes small. Spiracle length approximately 2x eye length. Nostrils thin. Nasal curtain broad and skirt-shaped. Mouth large with 5 oral papillae.
Disc densely covered in small, prickly denticles; denticles smaller towards disc margin. Pelvic fin posterior margins slightly posterior to disc. Tail broad based, shorter than disc width, with small dorsal/ventral finfolds. 1-3 irregular rows of thorns on midline from mid-disc to caudal sting. Thorns on tail larger than those on disc. Caudal sting origin positioned slightly posterior of mid tail.
Dorsum greenish-grey to greenish-brown with numerous irregular small yellow spots that sometimes form rosettes in larger animals. Ventrum mostly white with grey spots towards margin. Tail ventrally with yellow mottling.
Maximum disc width 45cm. Disc width at birth unknown.
Tropical freshwater river systems.
South America. Confined to the Parnaíba River watershed in northern Brazil.
Details of threats facing the Parnaíba river stingray are little known and studies are required. However, the species’ area of occurrence is experiencing a large expansion of human activities including urban development and agriculture. Dams are also impacting on its habitat. It is not known whether other threats facing other potamotrygonid species, such as fishing for consumption, the ornamental trade or persecution also affect this species.
Rosa, R., Pinto de Almeida, M. & Charvet-Almeida, P. 2009. Potamotrygon signata. The IUCN Red List of Threatened Species 2009: e.T161467A5430818. https://dx.doi.org/10.2305/IUCN.UK.2009-2.RLTS.T161467A5430818.en. Downloaded on 10 March 2021.
Presumably viviparous with trophodermic nutrition. Litter size unknown.
Diet consists mainly of insects, but also consumes molluscs, crustaceans, and small fishes.
Poorly known. Probably moves into seasonally flooded areas during periods of high water.
Reaction to divers
Unknown but probably difficult to approach.
There are no records of divers encountering Parnaíba freshwater stingrays in the wild. This isn’t particularly surprising as the Parnaíba River is extremely turbid. However, there may be clearer water in some of its tributaries.
The Parnaíba river stingray resembles many other small-spotted freshwater stingrays but it can be identified by it’s unique greenish-grey dorsal coloration.