Myliobatiformes Potamotrygonidae (the River Stingrays)
Jeff Guertin
11/27/07
Roughly 3-4 genera, 20 spp.
 4 genera
o Potamotrygon - most of the species
o Paratrygon
o Plesiotrygon
o 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
 Oral teeth are small with short cusps in usually less than 50 rows in either jaw
 Colorful dorsal arrangements
 Max salinity they can withstand is 15ppm (pure seawater is around 35ppm)
 Stings are continuously worn, shed and replaced
Distinctive Features
 Potamotrygon
o Sting is well developed and more posterior
o Finfolds posterior to caudal stings
o Eyes moderately large
 Paratrygon (one spp.)
o Slender whiplike tails, sting is reduced and located near tail base
o No finfolds
o Small eyes
 Plesiotrygon (one spp.)
o Slender whiplike tails, sting is well developed and more posterior
o Only ventral finfold
o Small eyes
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
Size, Age, & Growth
 Population doubling time ~14yrs
 Six are dwarf species with maximum sizes between 23 and 29 cm disk width
o P. humerosa, P. magdalenae, P. orbigvi, P. schuemacheri, P. vepezi, P. signata
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Others larger (80-90cm DW)
o Paratrygon aiereba, Potamotrygon brachvura
Females usually larger than males
Size at maturity for male Potamotrygonids 20-25 cm DW and females 24-32 cm DW
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
o 4 DD, 1 LC
 Generally considered harmless, not used in aquarium trade
 Thought to be threatened due to endemic nature
 Considered by most south americans to be dangerous due to their venomous sting, but not really
hunted
Bibliography
 Barbaro K.C. et al. 2007. 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. 2004. Biology of Sharks and Their Relatives. CRC Press,
Boca Raton.
 Florida Museum of National History. <http://www.flmnh.ufl.edu/fish/>. Downloaded on 25
November 2007.
 IUCN 2006. 2006 IUCN Red List of Threatened Species. <http://www.iucnredlist.org>.
Downloaded on 25 November 2007.
 Oldfield, R.G. 2005. Biology, husbandry, and reproduction of freshwater stingrays II. Tropical
Fish Hobbyist. 54(1): 110-112.
 Silva, TB. 2007. 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.