Myliobatiformes Potamotrygonidae Myliobatiformes Potamotrygonidae

(the River Stingrays(the River Stingrays))

Jeff GuertinJeff Guertin11/27/0711/27/07

Roughly 3-4 genera, 20 spp.Roughly 3-4 genera, 20 spp.

Most literature still lists under Rajiformes, not Myliobatiformes

4 genera Potamotrygon - most of the species Paratrygon Plesiotrygon amphi-American Himantura signifer (Family

Dasyatidae?)Dasyatidae?)

General CharacteristicsGeneral 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 individualUp to four stings may be present in one individual Oral teeth are small with short cusps in usually less Oral teeth are small with short cusps in usually less

than 50 rows in either jawthan 50 rows in either jaw Colorful dorsal arrangementsColorful dorsal arrangements

* Freshwater rays in asia and africa?

Distinctive FeaturesDistinctive 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 stingrayParatrygon aiereba - Discus Ray

Plesiotrygon iwamae - Long-Tailed River Stingray

HabitatHabitat

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 HabitsFood Habits

Carnivorous bottom feedersCarnivorous bottom feeders WormsWorms CrustaceansCrustaceans MollusksMollusks InsectsInsects CatfishCatfish

Size, Age, & GrowthSize, Age, & Growth

Population doubling time ~14yrs Six are Six are ddwarfwarf species with maximum sizes between 23 species with maximum sizes between 23

and 29 cm disk widthand 29 cm disk width P. humerosa, P. magdalenae, P. orbigvi, P. schuemacheri, P. humerosa, P. magdalenae, P. orbigvi, P. schuemacheri,

P. vepezi, P. signataP. vepezi, P. signata Others larger (80-90cm DW)Others larger (80-90cm DW)

Paratrygon aiereba, Potamotrygon brachvuraParatrygon aiereba, Potamotrygon brachvura Females usually larger than malesFemales usually larger than males Size at maturity for male Potamotrygonids 20-25 cm Size at maturity for male Potamotrygonids 20-25 cm

DW and females 24-32 cm DWDW and females 24-32 cm DW Gestation thought to be a little over 3 months.Gestation thought to be a little over 3 months.

ReproductionReproduction

Ovoviviparous (aplacentally viviparous) Seveloping embryos are nourished by uterine milk

secreted by trophonemata Both uteri are functional Usually between 2-7 pups/litter

ConservationConservation

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

BibliographyBibliography Barbaro K.C. et al. 2007. Comparative study on extracts from the tissue Barbaro K.C. et al. 2007. Comparative study on extracts from the tissue

covering the stingers of freshwater (covering the stingers of freshwater (Potamotrygon falkneriPotamotrygon falkneri) and marine ) and marine ((Dasyatis guttataDasyatis guttata) stingrays. Toxicon 50: 5. ) stingrays. Toxicon 50: 5.

Carrier, J,, Musick, J., and Heithaus, M. 2004. Biology of Sharks and Their Carrier, J,, Musick, J., and Heithaus, M. 2004. Biology of Sharks and Their Relatives. CRC Press, Boca Raton. Relatives. CRC Press, Boca Raton.

Florida Museum of National History. <http://www.flmnh.ufl.edu/fish/http://www.flmnh.ufl.edu/fish/>. Downloaded on 25 November 2007.

IUCN 2006. 2006 IUCN Red List of Threatened Species. IUCN 2006. 2006 IUCN Red List of Threatened Species. <http://www.iucnredlist.org>. Downloaded on 25 November 2007. <http://www.iucnredlist.org>. Downloaded on 25 November 2007.

Oldfield, R.G. 2005. Biology, husbandry, and reproduction of freshwater Oldfield, R.G. 2005. Biology, husbandry, and reproduction of freshwater stingrays II. stingrays II. Tropical Fish HobbyistTropical Fish Hobbyist. 54(1): 110-112.. 54(1): 110-112.

Silva, TB. 2007. Preliminary data on the feeding habits of the freshwater Silva, TB. 2007. Preliminary data on the feeding habits of the freshwater stingrays stingrays Potamotrygon falkneriPotamotrygon falkneri and and Potamotrygon motoroPotamotrygon motoro (Potamotrygonidae)from the Upper Parana River basin, Brazil. Biota (Potamotrygonidae)from the Upper Parana River basin, Brazil. Biota Neotropica v7.Neotropica v7.