Potamotrygon is a genus of freshwater stingrays in the family Potamotrygonidae native to the rivers of South America and sometimes seen in the aquarium trade. It inhabits rivers of tropical and subtropical climates, especially those of the Amazon basin and is virtually present in all South American countries, except for Chile.

Like other stingrays, the fishes of this genus have venomous barbs at the base of their tails, and their stings are dangerous to humans. Potamotrygon vary considerably in color, pattern and size, with the maximum disc width ranging from 31 cm (1 ft) in P. wallacei to 1.5 m (5 ft) in P. brachyura. There are currently more than 30 recognized extant (living) species in this genus.

The ocellate river stingray (Potamotrygon motoro), also known as the peacock-eye stingray or black river stingray, is a species of freshwater stingray in the family Potamotrygonidae. Potamotrygon motoro varies significantly in appearance and morphology over its large range.

Potamotrygon motoro, commonly known as the Ocellate River Stingray, is primarily found in the Paraná and Paraguay river basins of South America. This species inhabits tropical freshwater rivers, preferring calm waters with sandy substrates, particularly at the edges of brooks, streams, and lagoons. 

They are known to thrive in various river systems, including the Amazon, Uruguay, Paraná-Paraguay, and Orinoco basins. Their habitat depth typically ranges from 0.5 to 10 meters, and they are often found at temperatures between 24°C and 26°C.

Potamotrygon motoro can grow up to 50 cm (1.6 ft) in disc width, 1 m (3.3 ft) in total length and 34.2 kilograms (75 lb 6 oz) in weight. (though the official IGFA record is only 12.59 kg (27 lb 12 oz).

Its disk is roughly circular in shape, and its eyes are raised from the dorsal surface. The dorsal coloration is typically beige or brown, with numerous yellow-orange spots with dark rings. Its exact color, and the arrangement and size of the spots can vary significantly, both from individual to individual and depending on location.

Potamotrygon motoro the Ocellate river stingrays are sometimes kept in captivity, with requirements similar to other members of Potamotrygon. It is one of the most popular species of freshwater stingrays, but requires a very large tank. This species breeds readily in captivity and give birth to live pups.

The Potamotrygon motoro, also known as the ocellate river stingray, primarily feeds on a diet consisting of small fish, crustaceans, worms, and other invertebrates found on the riverbed. In the wild, they are carnivorous and spend most of their time searching for food in slow-moving waters with sandy or muddy bottoms. They are known to use their keen sense of smell and electroreception to locate prey hidden in the substrate.

Potamotrygon motoro, also known as the ocellate river stingray, is indeed highly venomous. It possesses a venomous tail barb that can cause painful stings and is known to cause serious injuries in humans. The venom can lead to severe pain, swelling, and even necrosis at the site of the sting. Therefore, handling this species requires extreme caution due to its potent venom.

Freshwater stingray accidents cause an immediate, intense, and unrelieved pain which is followed by edema, erythema and necrosis formation. Treatment for stingray envenomation is based on administration of analgesic, antipyretic and anti-inflammatory drugs. Concerning pain control, it is prescribed to immerse punctured limb on hot water to alleviate pain. There are no studies demonstrating specific targets on which stingray venom acts to promote pain.

Phylum : Chordata

Class : Chondrichthyes

Subclass : Elasmobranchii

Order : Myliobatiformes

Family : Potamotrygonidae

Genus : Potamotrygon

Species : P. motoro

Binomial name : Potamotrygon motoro

J. P. Müller & Henle, 1841

Synonyms :

Paratrygon laticeps Garman 1913

Potamotrygon alba Castex 1963

Potamotrygon circularis Garman 1913

Potamotrygon labradori Castex 1963

Potamotrygon laticeps Garman 1913

Potamotrygon pauckei Castex 1963

Taeniura motoro Müller & Henle 1841

Trygon garrapa Jardine 1843

Trygon mulleri Castelnau 1855