Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes (cartilaginous fishes)
Subclass: Elasmobranchii (sharks, rays and skates)
Order: Myliobatiformes
Family: Potamotrygonidae (river stingrays)

Genus/species: Potamotrygon motoro

GENERAL CHARACTERISTICS: Orange-spot Stingrays have an oval disc, with a greyish-brown upper surface patterned with distinct yellow-orange spots, and a white underside. Like most rays, flat teeth are used to grip and crush prey that is sucked into the ventral mouth. Note periscoping eyes which protrude from sand when buried. Olfaction is a major and well-developed means of perception for these stingrays; their olfactory organs are situated in laterally placed cartilaginous capsules on the top of the head. The spine on the tip of the tail is capable of delivering a painful sting.  Rays have an accessory respiratory opening, the Spiracle which is an adapted gill slit which has migrated to the top of the stingray. When the stingray is resting on the bottom the spiracle allows them to breathe.

Length up to 1 m (3 ft.) and weight up to 15 kg (33 lb.)


DISTRIBUTION: South America: Uruguay, Paraná- Paraguay, Orinoco, and Amazon Basins.

HABITAT: P. motoroare found in freshwater calm waters, especially on the sandy margins of lagoons, brooks and streams. They able to tolerate only a narrow range of salinities. Lost ability to retain urea decreasing osmolarity for fresh water unlike salt water relatives.

DIET IN THE WILD: They feed mostly on benthic hard-shelled invertebrates, such as clams, mussels, and crustaceans and also on worms, insect larvae, and small fishes.

REPRODUCTION: Fertilization is internal with the male attaches himself to a female by firmly clamping his jaws onto the posterior margin of her disk, sometimes leaving prominent bite marks. Females produce eggs that hatch inside the female and are then ‘born’ live after a gestation period of no more than three months. The litter size varies, from 3 to 21 young.

LIFESPAN: Maximum of 15 years in captivity.

CONSERVATION: IUCN Red list Data Deficient (DD)

REMARKS: P. motoro is one of the seven species of this genus inhabiting southern South America.

The Operculum pupillare inside the eye which controls the amount of light entering the eye. In dim light it will retract allowing greater light in and better vision at night.

They are not dangerous unless stepped on or threatened.

Fishermen also harpoon these rays during floods when they are found resting over vegetation in shallow water. P.motoro apparently has delicious meat.


California Academy of Sciences Steinhart Aquarium Flooded Forest Floor 2018

Ron’s flickr river stingrays

Ron’s flickr



Encyclopedia of Life

IUCN Red List

Ron’s WordPress shortlink