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Sea Life, Animals
& Exhibits

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Motoro Rays

(Potamotrygon motoro)
In this freshwater tank you will find Motoro Rays that are native to the freshwater of the Amazon Basin.

The motoro is one of three main species of the Potamotrygonidae family. The genus name, Potamotrygon, is from the Greek potamos that means ‘river’ and trygon, which means ‘three angles’, and may refer to its body shape. Stingrays are fish that have enlarged pectoral fins that connect around the body and head to form a disc. They do not have a dorsal fin, the ray will look relatively flat from the side, and the head will be even with the body. The eyes are located on the sides of the top of the head and directly behind them will lie the spiracles. The spiracles are openings in which water is pulled into the ray and over the gills to facilitate oxygen exchange.

Habitat

Freshwater river systems – calm waters, especially the sandy edges of lagoons, brooks and streams.

Diet

Motoro rays eat crustaceans, mollusks, and small fish that swim near the bottom.

Behavior

Stingrays have venomous spines along their tail that they use for defense. The spines are modified scales, tipped with barbs. Each spine has grooves on its underside that contain venom-producing soft tissue. If a ray feels threatened, it will erect the spines and use them to inject venom into the predator. The spines are constantly being shed and replaced. The venom affects the heart, lungs, and nervous system of the predator.

Females produce eggs, but these develop inside the female. The young hatch inside the female and are then ‘born’ live after a gestation period of no more than three months. The litter size varies massively, from 3 to 21 young.

Predators

There are very few natural predators to this type of stingray. Since these stingrays are found in freshwater, they do not have the threat of sharks, therefore, the main threat to these stingrays is overfishing. People commonly hunt them for food, particularly when water levels are low and they are easy to find. In some areas they are also hunted commercially. Habitat degradation and the construction of hydroelectric plants have also had an adverse effect on their environment.