Ocellate river stingray (Potamotrygon motoro)

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Ocellate river stingray, dorsal view
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Ocellate river stingray fact file

Ocellate river stingray description

KingdomAnimalia
PhylumChordata
ClassChondrichthyes
OrderRajiformes
FamilyPotamotrygonidae
GenusPotamotrygon (1)

Remarkable for its habitat, the ocellate river stingray is one of a small group of rays that evolved in freshwater from a marine ancestor (3). The first part of the scientific name reflects this lifestyle, potamos means ‘river’ in Greek, while the second part, trygon, means ‘three angles’ (4), and may refer to its body shape. The body of the ocellate river stingray is an oval disc, with a greyish-brown upper surface patterned with distinct yellow-orange spots, and a white underside (2). While the ocellate river stingray is a beautiful species, it is much feared for the single spine borne at the tip of the robust tail, which is capable of delivering a painful sting (2) (5).

Synonyms
Potamotrygon brachyuran, Potamotrygon paukei.
Size
Disc width: c. 100 cm (2)
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Ocellate river stingray biology

The ocellate river stingray is often found lying still, buried in the sandy sediment at the bottom of a stream, particularly during the warmest part of the day (2) (5). Like all stingrays, the females of this species produce eggs, but these develop inside the female. The young hatch inside the female and are then ‘born’ live after a gestation period of no more than three months (5) (6). The litter size of the ocellate river stingray varies massively, from 3 to 21 young (2). Sexual maturity is reached at around three years of age, when the stingray measures between 30 and 35 centimetres across (2).

Initially after birth, the ocellate river stingray feeds on plankton, but as it grows, the diet expands to also include small molluscs, crustaceans and the larvae of aquatic insects, while larger adults also eat certain catfish (those belonging to the family Loricaridae) (2). The ocellate has relatively few predators, except for some larger fish and caiman (3).

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Ocellate river stingray range

The ocellate river stingray has a widespread distribution, extending across Argentina, Brazil, Paraguay, Uruguay and Venezuela, where is occurs in the Paraná-Paraguay, Orinoco, and Amazon River basins (1).

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Ocellate river stingray habitat

While most rays are marine, the ocellate river stingray is one of the few species that is restricted entirely to freshwater (1) (5). Like the other river rays, this species favours calm waters, especially the sandy edges of lagoons, brooks and streams (2).

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Ocellate river stingray status

Classified as Data Deficient (DD) on the IUCN Red List (1).

IUCN Red List species status – Data Deficient

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Ocellate river stingray threats

Despite being the most abundant and widespread species of Potamotrygon endemic to South America, a lack of information on its life history and the status of populations means that it is not possible to determine the extent to which the ocellate river stingray may be threatened with extinction (1). However, what is known is that a number of factors may be having a detrimental affect on this species.

The ocellate river stingray is commonly hunted, with juveniles being taken for the ornamental fish trade and adults being captured for food (1) (2). When water levels in the streams and lagoons is low, or when the rivers flood and the rays can be found resting over vegetation in shallow water, the ocellate river stingray becomes an easy target for fishermen with harpoons. Some artisanal and commercial fishermen also catch this species on lines (2). Furthermore, habitat degradation in some parts of its range may threaten this species, such as the construction of hydroelectric plants and ports along the Río Paraná system (2).

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Ocellate river stingray conservation

A legal quota exists for the number of ocellate river stingrays that may be captured and exported, currently standing at 5,000 individuals per year, and it is said that its capture and exportation is monitored (7), although clearly, this does not in any way mitigate the threat of illegal hunting or trade. Further research on this species has been highly recommended, to enable its conservation status to be determined. Given the negative impacts of hunting and habitat degradation that the ocellate river stingray is subject to, it its possible that this freshwater stingray may be threatened (1).

View information on this species at the UNEP World Conservation Monitoring Centre.
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Find out more

To learn more about the conservation of rays visit

To learn more about conservation in the Río Paraná system see:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact: arkive@wildscreen.org.uk
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Glossary

Crustaceans
Diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.
Endemic
A species or taxonomic group that is only found in one particular country or geographic area.
Gestation
The state of being pregnant; the period from conception to birth.
Larvae
Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Molluscs
A diverse group of invertebrates, mainly marine, that have one or all of the following; a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.
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References

  1. IUCN Red List (June, 2008)
    http://www.iucnredlist.org
  2. Fowler, S.L., Cavanagh, R.D., Camhi, M., Burgess, G.H., Cailliet, G.M., Fordham, S.V., Simpfendorfer, C.A. and Musick, J.A. (2005) Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. IUCN/SSC Shark Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK.
  3. Burnie, D. (2001) Animal. Dorling Kindersley, London.
  4. Fishbase (October, 2008)
    http://www.fishbase.org/Summary/FamilySummary.cfm?ID=21
  5. Campbell, A. and Dawes, J. (2004) Encyclopedia of Underwater Life. Oxford University Press, Oxford.
  6. Thorson, T.B., Langhammer, J.K. and Oetinger, M.I. (1983) Reproduction and development of the South American freshwater stingrays Potamotrygon circularis and P. motoro. Environmental Biology of Fishes, 9(1): 3 - 24.
  7. Góes de Araújo, M.L., Charvet-Almeida, P., Almeida, M.P. and Pereira, H. (2004) Freshwater Stingrays (Potamotrygonidae): Status, Conservation and Management Challenges. Twentieth Meeting of the Animals Committee, CITES, Johannesburg, South Africa. Available at:
    http://www.cites.org/eng/com/AC/20/index.shtml
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Image credit

Ocellate river stingray, dorsal view  
Ocellate river stingray, dorsal view

© Paddy Ryan

Paddy Ryan
Ryan Photographic
2802 East 132nd Circle
Thornton
CO
80241
USA
Tel: +01 (303) 457 9795
paddyaryan@aol.com
http://www.ryanphotographic.com/

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