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Tan spots encircled with dark brown bands (ocelli) camouflage these slow-swimming ocellated rays as they lurk in the sand and mud. When prey come their way, rays quickly trap their catch under their bodies and then swallow their meal.
Ocellated river rays are flat and round with a tail that tapers to a poisonous stinger near the tip of the tail. They aren’t aggressive, but if they’re accidentally stepped on, the rays instantly lash their tails and stab with their poisonous stingers. Stingray wounds are extremely painful and may become infected—so remember to always shuffle your feet when you’re in stingray territory.
Like most rays and skates, ocellated rays have spiracles (holes) behind their eyes, with their mouths and gill slits underneath their bodies. When the rays lie on the river bottom, water enters the spiracles, passes over the gills and exits through the gill slits. The direction of the water flow keeps sand or mud from clogging the gills while supplying the rays with oxygen.
Experts don’t fully know the life history of freshwater rays and haven’t collected population data. However, we know these rays are a food source in some regions of the lower Amazon, and that in the past 15 years freshwater hobbyists have been buying river rays for home aquariums and other ornamental fish displays. As of 2002, 20,000 freshwater stingrays were being exported annually from Brazil. Since local residents and visitors fear these river rays (even more than they fear piranhas), agencies hire people to “clean up” river beaches by killing the stingrays. It has been estimated that in the last three years at least 21,000 stingrays were removed from the population.
The IUCN—The World Conservation Union—highly recommends making a population assessment since this ray’s geographic range is limited, and because major impacts—such as the clearing of rainforests—affect the river rays’ habitat.
Some scientists believe that freshwater rays once lived in the Pacific Ocean. During research, they found parasites living on Pacific Ocean rays that are similar to those living on freshwater rays. The scientists’ conclusion: the upheaval of the Andes mountains isolated the rays in freshwater rivers, where they’ve remained for 60,000,000 years.
Ocellated river rays hatch within the female’s uterus from soft-shelled egg cases. Uterine tissues secrete fluids which, in addition to egg yolks, supply the embryos with food during the five-month gestation period.