Myliobatiformes Potamotrygonidae (the River Stingrays ) Jeff Guertin 11/27/07

Roughly 3-4 genera, 20 spp. Most literature still lists under Rajiformes, not Myliobatiformes 4 genera Potamotrygon - most of the species Paratrygon Plesiotrygon Dasyatidae?) amphi-American Himantura signifer (Family Dasyatidae?)

General Characteristics Only family of batoids restricted to freshwater habitats* Generally medium to large sized batoids Dorsal surface of the disc and tail usually covered with many denticles, thorns and tubercles Up to four stings may be present in one individual Up to four stings may be present in one individual Oral teeth are small with short cusps in usually less than 50 rows in either jaw Oral teeth are small with short cusps in usually less than 50 rows in either jaw Colorful dorsal arrangements Colorful dorsal arrangements * Freshwater rays in asia and africa?

Distinctive Features Potamotrygon Sting is well developed and more posterior Finfolds posterior to caudal stings Eyes moderately large Paratrygon (one spp.) Slender whiplike tails, sting is reduced and located near tail base No finfolds Small eyes Plesiotrygon (one spp.) Slender whiplike tails, sting is well developed and more posterior Only ventral finfold Small eyes

Potamotrygon motoro - Ocellate river stingray Potamotrygon henlei - Polka-dot stingray Paratrygon aiereba - Discus Ray Plesiotrygon iwamae - Long-Tailed River Stingray

Habitat Tropical - only occur in South American rivers that drain into the Atlantic Ocean or Caribbean Sea Shallow areas Most species have distributions restricted to a single basin or river system, with only a few species present in more than one basin

Food Habits Carnivorous bottom feeders Carnivorous bottom feeders Worms Worms Crustaceans Crustaceans Mollusks Mollusks Insects Insects Catfish Catfish

Size, Age, & Growth Population doubling time ~14yrs Six are dwarf species with maximum sizes between 23 and 29 cm disk width Six are dwarf species with maximum sizes between 23 and 29 cm disk width P. humerosa, P. magdalenae, P. orbigvi, P. schuemacheri, P. vepezi, P. signata P. humerosa, P. magdalenae, P. orbigvi, P. schuemacheri, P. vepezi, P. signata Others larger (80-90cm DW) Others larger (80-90cm DW) Paratrygon aiereba, Potamotrygon brachvura Paratrygon aiereba, Potamotrygon brachvura Females usually larger than males Females usually larger than males Size at maturity for male Potamotrygonids cm DW and females cm DW Size at maturity for male Potamotrygonids cm DW and females cm DW Gestation thought to be a little over 3 months. Gestation thought to be a little over 3 months.

Reproduction Ovoviviparous (aplacentally viviparous) Seveloping embryos are nourished by uterine milk secreted by trophonemata Both uteri are functional Usually between 2-7 pups/litter

Conservation Only 5 listed on IUCN 4 DD, 1 LC Generally considered harmless, not used in aquarium trade Thought to be threatened due to endemic nature

Bibliography Barbaro K.C. et al Comparative study on extracts from the tissue covering the stingers of freshwater (Potamotrygon falkneri) and marine (Dasyatis guttata) stingrays. Toxicon 50: 5. Barbaro K.C. et al Comparative study on extracts from the tissue covering the stingers of freshwater (Potamotrygon falkneri) and marine (Dasyatis guttata) stingrays. Toxicon 50: 5. Carrier, J,, Musick, J., and Heithaus, M Biology of Sharks and Their Relatives. CRC Press, Boca Raton. Carrier, J,, Musick, J., and Heithaus, M Biology of Sharks and Their Relatives. CRC Press, Boca Raton. Florida Museum of National History.. Downloaded on 25 November IUCN IUCN Red List of Threatened Species.. Downloaded on 25 November IUCN IUCN Red List of Threatened Species.. Downloaded on 25 November Oldfield, R.G Biology, husbandry, and reproduction of freshwater stingrays II. Tropical Fish Hobbyist. 54(1): Oldfield, R.G Biology, husbandry, and reproduction of freshwater stingrays II. Tropical Fish Hobbyist. 54(1): Silva, TB Preliminary data on the feeding habits of the freshwater stingrays Potamotrygon falkneri and Potamotrygon motoro (Potamotrygonidae)from the Upper Parana River basin, Brazil. Biota Neotropica v7. Silva, TB Preliminary data on the feeding habits of the freshwater stingrays Potamotrygon falkneri and Potamotrygon motoro (Potamotrygonidae)from the Upper Parana River basin, Brazil. Biota Neotropica v7.