Potamotrygonidae

Source: Wikipedia, the free encyclopedia.

River stingrays
Ocellate river stingray, Potamotrygon motoro
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Batoidea
Order: Myliobatiformes
Suborder: Myliobatoidei
Superfamily: Dasyatoidea
Family: Potamotrygonidae
Garman, 1877
Type species
Potamotrygon histrix
J. P. Müller & Henle, 1841
Genera

Heliotrygon
Paratrygon
Plesiotrygon
Potamotrygon
Styracura

River stingrays or freshwater stingrays are

Dasyatidae). A single marine genus, Styracura
, of the tropical West Atlantic and East Pacific are also part of Potamotrygonidae. They are generally brownish, greyish or black, often with a mottled, speckled or spotted pattern, have disc widths ranging from 31 to 200 centimetres (1.0–6.6 ft) and venomous tail stingers. River stingrays feed on a wide range of smaller animals and the females give birth to live young. There are more than 35 species in five genera.

Distribution and habitat

Potamotrygon histrix is one of the most southernly distributed river stingrays, being found in the Río de la Plata Basin

They are native to tropical and

Atlantic as far south as the Río de la Plata in Argentina. A few generalist species are widespread, but most are more restricted and typically native to a single river basin.[1][2] The greatest species richness can be found in the Amazon, especially the Rio Negro, Tapajós, and Tocantins basins (each home to 8–10 species).[3] The range of several species is limited by waterfalls.[1]

Freshwaters inhabited by members of Potamotrygonidae vary extensively, ranging from

salinities up to at least 12.4‰.[1]

In 2016, two fully marine species formerly included in

Galápagos.[4][5]

Potamotrygonidae are the only family of

Urogymnus polylepis, the majority of species in this family are saltwater fish.[8]

Characteristics

Potamotrygon leopoldi is part of a species complex of blackish river rays with contrasting pale spots found in the Tapajós, Xingu and Tocantins basins[3]

River stingrays are almost circular in shape, and range in size from

piraíba catfish (Brachyplatystoma filamentosum).[12] In each species in the family Potamotrygonidae, females reach a larger size than the males.[1]

The upper surface is covered with

denticles (sharp tooth-like scales). Most species are brownish or greyish and often have distinctive spotted or mottled patterns, but a few species are largely blackish with contrasting pale spots.[3][13] Juveniles often differ, in some species greatly, in colour and pattern from the adults.[3]

Behavior

Potamotrygon henlei and its close relatives (e.g., P. leopoldi) mainly feed on snails in the wild, but easily adapt to a more generalized diet in captivity[1][14]

Feeding

Members of Potamotrygonidae are predators and feed on a wide range of animals such as insects, worms,

nocturnal.[1]

Breeding

Plesiotrygon iwamae is easily identified as male by its claspers
, the pair of elongated structures at the base of the tail

Like other

trophonemata glands.[1][16][17] Depending on exact species, the gestation period is 3 to 12 months and there are between 1 and 21 young in each litter.[1][18] The breeding cycle is generally related to flood levels.[16]

Relationship with humans

Potamotrygon motoro
are barely visible (eye center-right on photo) and easily stepped on

Sting

Main article: Stingray injury

Like other

Neotropical region because of the injuries they can cause.[21][22][23] In Colombia alone, more than 2,000 injuries are reported per year.[24] Freshwater stingrays are generally non-aggressive,[24] and the stingers are used strictly in self-defense.[25] As a consequence injuries typically occur when bathers step on them (injuries to feet or lower legs) or fishers catch them (injuries to hands or arms).[25] In addition to pain caused by the barbed stinger itself and the venom, bacterial infections of the wounds are common and may account for a greater part of the long-term problems in stinging victims than the actual venom.[25] The stings are typically highly painful and are occasionally fatal to humans, especially people living in rural areas that only seek professional medical help when the symptoms have become severe.[25] In general, relatively little is known about the composites of the venom in freshwater stingrays, but it appears to differ (at least in some species) from that of marine stingrays.[25] There are possibly also significant differences between the venoms of the various Potamotrygonidae species.[26] Due to the potential danger they represent, some locals strongly dislike freshwater stingrays and may kill them on sight.[18] A study at the Butantan Institute, São Paulo, Brazil, revealed that the composition of freshwater stingray venom varies according to sex and age, even between individuals of the same species. Each time the environment changes, the feeding of the stingray changes, leading to changes in the composition of toxins and toxicological effects. There is no specific antidote or treatment for freshwater stingray venom.[27]

Symptomatology

Accidents occur when the rays are stepped on or when the fins are touched, the defensive behavior consists of turning the body, moving the tail and introducing the stinger into the victim. Generally, stingers are inserted into the feet and heels of bathers and the hands of fishermen. Initial symptoms include severe pain,

secondary infection, usually caused by Pseudomonas and Staphylococcus. If the stinger reaches internal organs, it can be fatal.[28]

As food

Freshwater stingrays are often caught by hook-and-line and as bycatch in trawls. In the Amazon, Paratrygon and certain Potamotrygon are the most caught species and the first is the most sought.[29] In the Río de la Plata region, the meat of P. brachyura is particularly prized and locally the species is called raya fina (fine ray).[30] Freshwater rays weighing less than 2 kg (4.4 lb) are generally discarded, but have a low survival rate.[29] Their meat is mainly consumed locally, but is also exported to Japan and South Korea.[29] From 2005 to 2010, the reported capture in the Brazilian states of Amazonas and Pará has ranged between 584.5 and 1,104.5 metric tons (575.3–1,087.1 long tons) per year.[29] In contrast, some fishers believe they only can be used for traditional medicine, incorrectly thinking that the meat (not just the tail region around the stinger) is toxic.[31]

In captivity

Potamotrygon jabuti is a valuable species in the aquarium trade, but export of wild-caught individuals from Brazil (as opposed to captive bred) is illegal.[29]

Freshwater stingrays are often kept in aquariums, but require a very large tank and will eat small tank mates.

Potamotrygon motoro are considered relatively hardy in a captive setting,[33] while others such as Paratrygon aiereba, Plesiotrygon nana and Potamotrygon tigrina are much more difficult to maintain.[26]

Several species are commonly bred in captivity, especially at East and Southeast Asian

fish farms, which produce thousands of offspring each year.[18] The more serious captive breeding efforts only began in the late 1990s when Brazil put in restrictions on their export of wild-caught individuals.[18] Some captive farms produce hybrids (both intentionally to get offspring with new patterns and unintentionally because of a lack of males), but this practice is generally discouraged.[18][26] In several US states there are regulations in place that limit the keeping of freshwater stingrays.[26]

Conservation

Potamotrygon tigrina is an endangered species that only was scientifically described in 2011[34]

The status of most species is relatively poorly known, but overall it is suspected that river stingrays are declining due to capture (for food and the aquarium industry) and habitat loss (mainly due to dams and pollution from mining).[29]

Zoos and

studbooks, for several Potamotrygonidae species.[26][35]

Dams

Some freshwater rays are threatened by dams, but Potamotrygon falkneri was able to spread to the upper Paraná basin due to the Itaipu Dam[36]

Dams represent a risk to some species, but others may benefit from them. For example, the

lentic habitats, including the reservoirs created by river impoundment.[12]

Fishing and capture

In addition to the large numbers caught for food (hundred of tons per year in the Brazilian Amazon alone),[29] many are killed because of the risk their stings represent to locals and tourists. In the Amazon, it has been estimated that many thousand river stingrays are removed from certain areas to minimize the risk to ecotourism.[7] Such removal is unregulated by the authorities, as not considered fishing in the traditional sense.[7]

Initially Brazil completely banned all exports of wild-caught freshwater stingrays for the aquarium trade, but have since introduced quotas for some species. From 2010 to 2015, between c. 4,600 and 5,700 of six species (the vast majority were

Appendix II.[41][43]

Taxonomy and species

The

sister genera, and Plesiotrygon and Potamotrygon are sister genera.[44]

Subfamily Styracurinae

The two Styracura (here S. schmardae) are the only members of the family from marine waters[5]

Subfamily Potamotrygoninae

At up to 1.6 m (5.2 ft) in disc width and 110 kg (240 lb) in weight, Paratrygon aiereba is one of the largest species in the family[8]
Plesiotrygon (here P. iwamae with part of tail missing) is very long-tailed compared to other genera in the family[3]
Potamotrygon motoro
 is one of the best-known and most widespread species in the family

See also

References

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  2. ^ a b Duncan, W.P.; M.N. Fernandes (2010). "Physicochemical characterization of the white, black, and clearwater rivers of the Amazon Basin and its implications on the distribution of freshwater stingrays (Chondrichthyes, Potamotrygonidae)". PanamJAS. 5 (3): 454–464.
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  6. ^ Compagno, L. J. V. & S. F. Cook (1995) "The exploitation and conservation of freshwater elasmobranchs: status of taxa and prospects for the future". In: The Biology of Freshwater Elasmobranchs. Oetinger, M. I. & Zorzi, G. D. (eds.). Journal of Aquariculture & Aquatic Sciences, 7: 62–90.
  7. ^ a b c d Góes de Araújo, M.L.; P. Charvet-Almeida; M.P. Almeida; H. Pereira (2004). "Freshwater Stingrays (Potamotrygonidae): status, conservation and management challenges". Information Document. AC 20 (8): 1–6.
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  10. ^ Froese, Rainer; Pauly, Daniel (eds.) (2017). "{{{1}}} schmardae" in FishBase. January 2017 version.
  11. ^ Oddone M.C., Velasco G., Rincon G. (2008). "Occurrence of freshwater stingrays (Chondrichthyes: Potamotrygonidae) in the Uruguay River and its tributaries, Uruguay, South America". International Journal of Ichthyology. 14 (2): 69–76.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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  14. ^ Shibuya, A.; M.L.G. Araújo; J.A.S. Zuanon (2009). "Analysis of stomach contents of freshwater stingrays (Elasmobranchii, Potamotrygonidae) from the middle Negro River, Amazonas, Brazil". Pan-American Journal of Aquatic Sciences. 4 (4): 466–475.
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  18. ^ a b c d e f Bleher, H.yn (13 June 2016). "Definitive guide to South American freshwater rays". Practical Fishkeeping. Retrieved 26 October 2017.
  19. ^ Wheeler, Quentin (10 April 2011). "New to Nature No 37: Heliotrygon stingrays". The Guardian. Retrieved 25 October 2017.
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  21. ^ Froese, Rainer, and Daniel Pauly, eds. (2017). "Potamotrygonidae" in FishBase. January 2017 version.
  22. ^ Froese, Rainer; Pauly, Daniel (eds.) (2017). "Potamotrygon schuhmacheri" in FishBase. January 2017 version.
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  24. ^ a b Grenard, S. "Stingray injuries, envenomation, and medical management". potamotrygon.de. Retrieved 22 October 2017.
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  27. ^ "Freshwater stingray venom varies according to sex and age". AGÊNCIA FAPESP. Retrieved 2020-10-20.
  28. ^ https://tede.ufam.edu.br/bitstream/tede/2622/1/Juliana%20Luiza%20Varj%C3%A3o%20Lameiras.pdf [bare URL PDF]
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  41. ^ a b Listing of the species Potamotrygon motoro and Potamotrygon schroederi in Appendix II in accordance with Article II 2a (b) of the Convention, and Resolution Conf. 9.24 (Rev. CoP15), Sixteenth meeting of the Conference of the Parties Bangkok (Thailand), CITES, 3–14 March 2013, pp. 1–22
  42. ^ "Appendices I, II and III". CITES. 4 October 2017. Retrieved 26 October 2017.
  43. ^ "17.246 to 17.249 Freshwater stingrays (Potamotrygonidae spp.)". CITES. Archived from the original on 28 October 2017. Retrieved 26 October 2017.
  44. ^ a b De Carvalho, M.R.; N.R. Lovejoy (2011). "Morphology and phylogenetic relationships of a remarkable new genus and two new species of Neotropical freshwater stingrays from the Amazon basin (Chondrichthyes: Potamotrygonidae)". Zootaxa (2776): 13–48.
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  • Ross, Richard (1999) Freshwater Stingrays, Aqualog Special,p49
  • Ross, Richard (2000) Freshwater Rays, Aqualog, p140
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