Atlantic Stingray - Biology and Ecology

Biology and Ecology

The Atlantic stingray feeds mostly on benthic invertebrates such as bivalves, tube anemones, amphipods, crustaceans, and nereid worms, which they locate using their electroreceptive ampullae of Lorenzini. The exact composition of their diet varies by geographical location. When feeding, these rays will position themselves facing the current so that the sediment will be washed away. Numerous species of sharks, such as the tiger shark (Galeocerdo cuvier) and the bull shark (Carcharhinas leucas), are major predators of the Atlantic stingray. In freshwater habitats, they may be preyed upon by American alligators (Alligator mississippiensis). A known parasite of freshwater Atlantic stingrays is Argulus, a fish louse that feeds on skin mucus.

Despite having a regular freshwater presence, the Atlantic stingray is physiologically euryhaline and no population has evolved the specialized osmoregulatory mechanisms found in the river stingrays of the family Potamotrygonidae. This may be due to the relatively recent date of freshwater colonization (under one million years), and/or possibly incomplete genetic isolation of the freshwater populations, as they remain capable of surviving in salt water. Freshwater Atlantic stingrays have only 30-50% the concentration of urea and other osmolytes in their blood compared to marine populations. However, the osmotic pressure between their internal fluids and external environment still causes water to diffuse into their bodies, and they must produce large quantities of dilute urine (at 10 times the rate of marine individuals) to compensate.

Like other stingrays, the Atlantic stingray is ovoviviparous. Both marine and freshwater populations in Florida have an annual mating season from September or October to April, though ovulation does not occur until late March or early April. Courtship involves the male following the female and biting at her body and fins, and the male will grip onto the female's pectoral fin to assist in copulation. The embryos are sustained by a yolk sac until around day 60, after which they are nourished by uterine milk secreted by the mother. Litters of 1-4 young are born from late July to early August, after a gestation period of 4-4.5 months. Newborns measure 10–13 centimetres (3.9–5.1 in) wide. Marine males mature at a disk width of 20 cm (7.9 in) and females at a disk width of 24 cm (9.4 in). Freshwater males mature at a disk width of 21 cm (8.3 in) and females at a disk width of 22 cm (8.7 in).