Giant freshwater stingray

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Giant freshwater stingray
Himantura polylepis.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Batoidea
Order: Myliobatiformes
Family: Dasyatidae
Genus: Urogymnus
Species:
U. polylepis
Binomial name
Urogymnus polylepis
(Bleeker, 1852)
Himantura polylepis rangemap.png
Geographic range (excludes populations not confirmed as extant and/or conspecific) [1]
Synonyms
  • Himantura chaophraya Monkolprasit & Roberts, 1990
  • Trygon polylepisBleeker, 1852
  • Himantura polylepsis(Bleeker, 1852)

The giant freshwater stingray (Urogymnus polylepis, also widely known by the junior synonym Himantura chaophraya) is a species of stingray in the family Dasyatidae. It is found in large rivers and estuaries in Southeast Asia and Borneo, though historically it may have been more widely distributed in South and Southeast Asia. The widest freshwater fish and the largest stingray in the world, this species grows up to 2.2 m (7.2 ft) across and can reach up to 300 kg (660 lb) in weight. It has a relatively thin, oval pectoral fin disc that is widest anteriorly, and a sharply pointed snout with a protruding tip. Its tail is thin and whip-like, and lacks fin folds. This species is uniformly grayish brown above and white below; the underside of the pectoral and pelvic fins bear distinctive wide, dark bands on their posterior margins.

Contents

Bottom-dwelling in nature, the giant freshwater stingray inhabits sandy or muddy areas and preys on small fishes and invertebrates. Females give live birth to litters of one to four pups, which are sustained to term by maternally produced histotroph ("uterine milk"). This species faces heavy fishing pressure for meat, recreation, and aquarium display, as well as extensive habitat degradation and fragmentation. These forces have resulted in substantial population declines in at least central Thailand and Cambodia. As a result, the International Union for Conservation of Nature (IUCN) has assessed the giant freshwater stingray as Endangered.

Taxonomy and phylogeny

The first scientific description of the giant freshwater stingray was authored by Dutch ichthyologist Pieter Bleeker in an 1852 volume of the journal Verhandelingen van het Bataviaasch Genootschap van Kunsten en Wetenschappen. His account was based on a juvenile specimen 30 cm (12 in) across, collected from Jakarta, Indonesia. Bleeker named the new species polylepis, from the Greek poly ("many") and lepis ("scales"), and assigned it to the genus Trygon (now a synonym of Dasyatis ). [2] [3] However, in subsequent years Bleeker's description was largely overlooked, and in 1990 the giant freshwater stingray was described again by Supap Monkolprasit and Tyson Roberts in an issue of the Japanese Journal of Ichthyology. [4] They gave it the name Himantura chaophraya, which came into widespread usage. In 2008, Peter Last and B. Mabel Manjaji-Matsumoto confirmed that T. polylepis and H. chaophraya refer to the same species, and since Bleeker's name was published earlier, the scientific name of the giant freshwater stingray became Himantura polylepis. [1] [5] This species may also be called the giant freshwater whipray, giant stingray, or freshwater whipray. [6]

There is a complex of similar freshwater and estuarine stingrays in South Asia, Southeast Asia, and Australasia that are or were tentatively identified with U. polylepis. The Australian freshwater Urogymnus were described as a separate species, Urogymnus dalyensis , in 2008. The freshwater Urogymnus in New Guinea are probably U. dalyensis rather than U. polylepis, though confirmation awaits further study. [5] Trygon fluviatilis from India, as described by Nelson Annandale in 1909, closely resembles and may be conspecific with U. polylepis. [4] On the other hand, comparison of freshwater whipray DNA and amino acid sequences between India and Thailand has revealed significant differences. [7] Finally, additional research is needed to assess the degree of divergence amongst populations of U. polylepis inhabiting various drainage basins across its distribution, so as to determine whether further taxonomic differentiation is warranted. [1]

In terms of the broader evolutionary relationships between the giant freshwater whipray and the rest of the family Dasyatidae, a 2012 phylogenetic analysis based on mitochondrial DNA reported that it was most closely related to the porcupine ray (Urogymnus asperrimus), and that they in turn formed a clade with the mangrove whipray (U. granulatus) and the tubemouth whipray (U. lobistoma). This finding adds to a growing consensus that the genus Himantura sensu lato is paraphyletic. [8]

Description

Preserved giant freshwater stingray, showing the characteristic shape of its disc. Giant freshwater stingray.JPG
Preserved giant freshwater stingray, showing the characteristic shape of its disc.

The giant freshwater stingray has a thin, oval pectoral fin disc slightly longer than wide and broadest towards the front. The elongated snout has a wide base and a sharply pointed tip that projects beyond the disc. The eyes are minute and widely spaced; behind them are large spiracles. Between the nostrils is a short curtain of skin with a finely fringed posterior margin. The small mouth forms a gentle arch and contains four to seven papillae (two to four large at the center and one to four small to the sides) on the floor. The small and rounded teeth are arranged into pavement-like bands. There are five pairs of gill slits on the ventral side of the disc. The pelvic fins are small and thin; mature males have relatively large claspers. [3] [4]

The thin, cylindrical tail measures 1.8–2.5 times as long as the disc and lacks fin folds. A single serrated stinging spine is positioned on the upper surface of the tail near the base. [3] At up to 38 cm (15 in) long, the spine is the largest of any stingray species. [9] There is band of heart-shaped tubercles on the upper surface of the disc extending from before the eyes to the base of the sting; there is also a midline row of four to six enlarged tubercles at the center of the disc. The remainder of the disc upper surface is covered by tiny granular denticles, and the tail is covered with sharp prickles past the sting. This species is plain grayish brown above, often with a yellowish or pinkish tint towards the fin margins; in life the skin is coated with a layer of dark brown mucus. The underside is white with broad dark bands, edged with small spots, on the trailing margins of the pectoral and pelvic fins. The tail is black behind the spine. [3] [4] [10] The giant freshwater stingray reaches at least 1.9 m (6.2 ft) in width and 5.0 m (16.4 ft) in length, and can likely grow larger (It is not impossible that length is even 10 m (33 ft), and width is 5 m (16 ft)). [10] With reports from the Mekong and Chao Phraya Rivers of individuals weighing 500–600 kg (1,100–1,300 lb), but it is not impossible, that it is 1,500 kg (3,300 lb), or even 2,000 kg (4,400 lb) - it ranks among the largest freshwater fishes in the world. [4] [9]

In June 2022, it was reported that a specimen caught in the Mekong river had broken the record for the largest strict freshwater fish ever documented (the largest sturgeon species can far exceed this size, but they are anadromous). The individual weighed 300 kg (660 lb), and was measured at 3.98 m (13.1 ft) long and 2.2 m (7.2 ft) wide. [11]

Distribution and habitat

The giant freshwater stingray is known to inhabit several large rivers and associated estuaries in Indochina and Borneo. In Indochina, it occurs in the Mekong River to potentially as far upstream as Chiang Khong in Thailand, as well as in the Chao Phraya, Nan, Mae Klong, Bang Pakong, and Tapi Rivers, also found in Bueng Boraphet but now completely extinct. In Borneo, this species is found in the Mahakam River in Kalimantan and the Kinabatangan and Buket Rivers in Sabah; it is reportedly common in the Kinabatangan River but infrequently caught. Though it has been reported from Sarawak as well, surveys within the past 25 years have not found it there. Elsewhere in the region, recent river surveys in Java have not recorded its presence, despite the island being the locality of the species holotype.

Historical records from the Ganges River in India, and the Bay of Bengal as Trygon fluviatilis are possibly Himantura fluviatilis , although it has been confirmed as being present the Kaladan and Mayu rivers in Myanmar in 2022. [12]

Disjunct populations of the giant freshwater stingray in separate river drainages are probably isolated from one another; though the species occurs in brackish environments, there is no evidence that it crosses marine waters. This is a bottom-dwelling species that favors a sandy or muddy habitat. [1] Unexpectedly, it can sometimes be found near heavily populated urban areas. [9]

Biology and ecology

The diet of the giant freshwater stingray consists of small, benthic fishes and invertebrates such as crustaceans and molluscs, which it can detect using its electroreceptive ampullae of Lorenzini. [9] [10] Individuals can often be seen at the edge of the river, possibly feeding on earthworms. [1] [13] Parasites documented from this species include the tapeworms Acanthobothrium asnihae , A. etini , A. masnihae , A. saliki , A. zainali , [14] Rhinebothrium abaiensis , R. kinabatanganensis , and R. megacanthophallus . [15] The giant freshwater stingray is viviparous, with the developing embryos nourished initially by yolk and later by histotroph ("uterine milk") provided by the mother. [6] This species does not appear to be diadromous (migrating between fresh and salt water to complete its life cycle). Observed litter sizes range from one to four pups; newborns measure around 30 cm (12 in) across. Pregnant females are frequently found in estuaries, which may serve as nursery areas. Males mature sexually at approximately 1.1 m (3.6 ft) across; female maturation size and other life history details are unknown. [1] [4]

Human interactions

Stingrays on display at the aquarium Urogymnus polylepis at Itabashi Botanical Garden.png
Stingrays on display at the aquarium

The giant freshwater stingray is not aggressive, but its sting is sheathed in toxic mucus and is capable of piercing bone. [9] Across its range, this species is caught incidentally by artisanal fishers using longlines, and to a lesser extent gillnets and fish traps. [10] [16] It is reputedly difficult and time-consuming to catch; a hooked ray may bury itself under large quantities of mud, becoming almost impossible to lift, or drag boats over substantial distances or underwater. [9] The meat and the cartilage are used; large specimens are cut into kilogram pieces for sale. [6] Adults that are not used for food are often killed or maimed by fishers nonetheless. [16] In the Mae Klong and Bang Pakong Rivers, the giant freshwater stingray is also increasingly targeted by sport fishers and for display in public aquariums. These trends pose conservation concerns; the former because catch and release is not universally practised and the post-release survival rate is unknown, the latter because this species does not survive well in captivity. [1]

The major threats to the giant freshwater stingray are overfishing and habitat degradation resulting from deforestation, land development, and damming. The construction of dams also fragments the population, reducing genetic diversity and increasing the susceptibility of the resulting subpopulations to extinction. [16] Due to its low reproductive rate, the giant freshwater stingray is not resilient to anthropogenic pressures. In central Thailand and Cambodia, the population is estimated to have been reduced by 30–50% over the past 20–30 years, with declines as severe as 95% in some locations. The size of rays caught has decreased significantly as well; for example, in Cambodia the average weight of a landed ray has dropped from 23.2 kg (51 lb) in 1980 to 6.9 kg (15 lb) in 2006. The status of populations in other areas, such as Borneo, is largely unknown. As a result of documented declines, the International Union for Conservation of Nature (IUCN) has assessed this species as Endangered overall, and as Critically Endangered in Thailand. [1] [17] In the 1990s, the Thai government initiated a captive breeding program at Chai Nat to bolster the population of this and other freshwater stingray species until the issue of habitat degradation can be remedied. However, by 1996 the program had been put on hold. [16]

Related Research Articles

<span class="mw-page-title-main">Roughback whipray</span> Species of cartilaginous fish

The roughback whipray is a rare species of freshwater stingray in the family Dasyatidae, found over sandy bottoms in the Mae Klong and Chao Phraya Rivers of Thailand. Growing no more than 29 cm (11 in) across, this small ray has an oval pectoral fin disc and a whip-like tail without fin folds. It closely resembles the white-edge freshwater whipray in appearance, but can be distinguished by its coloration: light gray to dark orange-brown above and white below with a dark band along the lateral margins. Another identifying feature is a "pearl organ" at the center of the back, found in individuals of all ages. All of the original specimens of the roughback whipray were found with extensive wounds to the fins and tail. The International Union for Conservation of Nature (IUCN) has assessed this species as Endangered, citing the extensive habitat degradation and heavy fishing pressure within its limited range.

<i>Himantura</i> Genus of cartilaginous fishes

Himantura is a genus of stingray in the family Dasyatidae that is native to the Indo-Pacific. In a 2016 taxonomic revision, many of the species formerly assigned to Himantura were reassigned to other genera.

<span class="mw-page-title-main">Estuary stingray</span> Species of cartilaginous fish

The estuary stingray, also called the estuary stingaree or brown stingray, is a species of stingray in the family Dasyatidae. Endemic to eastern Australia, it typically inhabits shallow, mangrove-lined tidal rivers, estuaries, and bays in southern Queensland and New South Wales. This yellow-brown to olive ray grows to at least 93 cm (37 in) across. It has a diamond-shaped pectoral fin disc and a mostly smooth, whip-like tail bearing both dorsal and ventral fin folds. It can additionally be identified by its long, narrow nostrils and the row of thorns along the midline of its back.

<span class="mw-page-title-main">Mekong freshwater stingray</span> Species of cartilaginous fish

The Mekong freshwater stingray, Hemitrygon laosensis, is a species of stingray in the family Dasyatidae, restricted to the Mekong and Chao Phraya Rivers in Laos and Thailand; the occurrence in Chao Phraya is considered an introduction. Measuring up to 62 cm (24 in) across, this ray has an oval pectoral fin disc, a tail with both upper and lower fin folds, and a midline row of spine-like dermal denticles. A characteristic feature of this species is its bright orange underside. The Mekong freshwater stingray preys on invertebrates and is aplacental viviparous. It has been assessed as Endangered by the International Union for Conservation of Nature (IUCN), as it is threatened by overfishing and habitat degradation.

<i>Himantura fluviatilis</i> Species of cartilaginous fish

Himantura fluviatilis, the Ganges whip ray, is an obscure species of stingray in the family Dasyatidae, apparently endemic to the Ganges River system and adjacent marine waters. With an oval pectoral fin disc and long projecting snout, it closely resembles, and may be the same species as Himantura chaophraya. Growing to 1.4 m (4.6 ft) across, it is a plain dark colour above, and lighter below with wide dark bands on the lateral disc margins. The International Union for Conservation of Nature (IUCN) has listed this species as Endangered, as it faces overfishing and habitat degradation within its heavily populated range.

<span class="mw-page-title-main">Marbled whipray</span> Species of cartilaginous fish

The marbled whipray is a little-known species of stingray in the family Dasyatidae, native to several freshwater rivers in Southeast Asia. This species has an oval pectoral fin disc with an elongated, pointed snout and a very long, whip-like tail without fin folds. It is characterized by numerous heart-shaped dermal denticles and tubercles on its upper surface, as well as a reticulated pattern of brown blotches on a light background. The maximum recorded disc width is 36 cm (14 in). The marbled whipray has been assessed as Endangered by the International Union for Conservation of Nature (IUCN); it is heavily threatened by fishing and habitat loss, degradation, and fragmentation.

<span class="mw-page-title-main">White-edge freshwater whipray</span> Species of cartilaginous fish

The white-edge freshwater whipray is an extremely rare species of stingray in the family Dasyatidae, native to four river systems in Southeast Asia. Measuring up to 60 cm (24 in) across, this ray has an oval pectoral fin disc and a very long, whip-like tail without fin folds. It can be identified by the presence of a sharply delineated white band running around the margin of its otherwise brown disc, as well as by its white tail and a band of dermal denticles along the middle of its back. This species feeds on benthic invertebrates and is aplacental viviparous. Its two long tail spines are potentially dangerous to humans. The International Union for Conservation of Nature (IUCN) has assessed the white-edge freshwater whipray as Endangered, as it is under heavy pressure from fishing and habitat loss, degradation, and fragmentation.

<i>Urogymnus</i> Genus of cartilaginous fishes

Urogymnus is a genus of stingrays in the family Dasyatidae from marine, brackish and freshwater habitats in the Indo-Pacific and tropical East Atlantic regions. The genus was previously considered to be monotypic, containing only the porcupine ray. Molecular phylogenetic research published in 2016 reassigned several species from Himantura to Urogymnus.

<span class="mw-page-title-main">Whiptail stingray</span> Family of fishes

The whiptail stingrays are a family, the Dasyatidae, of rays in the order Myliobatiformes. They are found worldwide in tropical to temperate marine waters, and a number of species have also penetrated into fresh water in Africa, Asia, and Australia. Members of this family have flattened pectoral fin discs that range from oval to diamond-like in shape. Their common name comes from their whip-like tails, which are much longer than the disc and lack dorsal and caudal fins. All whiptail stingrays, except the porcupine ray, have one or more venomous stings near the base of the tail, which is used in defense. In order to sting their victims, they jerk their tails as the stinger falls off and stays in the wound that they have created. The stinger of a whiptail stingray is pointy, sharp with jagged edges. They range in size from 0.18 to 2.0 m or more across in the case of the smalleye stingray and giant freshwater stingray.

<span class="mw-page-title-main">Mangrove whipray</span> Species of cartilaginous fish

The mangrove whipray or whitetail stingray, is a species of stingray in the family Dasyatidae. It is widely distributed in the Indo-Pacific region from the Red Sea to northern Australia and Micronesia. A benthic inhabitant of shallow inshore waters, juvenile mangrove whiprays favor mangrove and estuarine habitats, while adults favor sandy to rocky areas in lagoons and coral reefs. This species can be identified by its thick, oval pectoral fin disc that is dark gray above with numerous white flecks, and by its relatively short, whip-like tail that is white past the stinging spine. It grows up to 1.4 m (4.6 ft) across.

<span class="mw-page-title-main">Reticulate whipray</span> Species of fish

The reticulate whipray or honeycomb stingray is a species of stingray in the family Dasyatidae. It inhabits coastal waters in the western Indian Ocean including the Red Sea, Natal and the Arabian Sea; also a Lessepsian transmigrant in the eastern Mediterranean. A large species reaching 2 m (6.6 ft) in width, the reticulate whipray has a diamond-shaped pectoral fin disc and an extremely long tail without fin folds. Both its common and scientific names refer to its ornate dorsal color pattern of many small, close-set dark spots or reticulations on a lighter background. However, the reticulate whipray is only one of several large spotted stingrays in the Indo-Pacific which, coupled with the variability of its coloration with age and locality, has resulted in a great deal of taxonomic confusion.

<span class="mw-page-title-main">Pink whipray</span> Species of stingray in the family Dasyatidae

The pink whipray is a species of stingray in the family Dasyatidae, with a wide but ill-defined distribution in the tropical Indo-Pacific from southern Africa to Polynesia. It is a bottom dweller that generally inhabits shallow water under 70 m (230 ft) deep, in sandy areas associated with coral reefs. Individuals exhibit a high degree of fidelity to particular locations. The pink whipray has a diamond-shaped pectoral fin disc wider than long, with a broad-angled snout and a very long, whip-like tail without fin folds. It has only a few small thorns on its back and is uniform brownish to grayish pink in color, becoming much darker past the tail sting. This large ray can reach 1.8 m (5.9 ft) across and over 5 m (16 ft) long.

<span class="mw-page-title-main">Freshwater whipray</span> Species of fish

The freshwater whipray is a little-known species of stingray in the family Dasyatidae, found in a number of large rivers and associated estuaries in northern Australia. Until recently, this species was regarded as a regional subpopulation of the similar-looking but much larger giant freshwater stingray of Southeast Asia. Typically reaching 1 m (3.3 ft) across, the freshwater whipray has a distinctively shaped, rounded pectoral fin disc, a projecting snout, and a thin tail without fin folds. It is plain brown above and white below with dark marginal bands. It may occasionally travel onto land and can "breathe" out of water for up to 7 minutes. The freshwater whipray is an active hunter of small fishes and shrimps, and does not currently face substantial conservation threats.

The tubemouth whipray is a little-known species of stingray in the family Dasyatidae, named for its distinctive, highly protrusible jaws. It is found in shallow, brackish water near mangrove forests and large river mouths along the coasts of southwestern Borneo and southern Sumatra. Measuring up to 1 m (3.3 ft) across, this species has a diamond-shaped pectoral fin disc with an elongated, pointed snout and broadly rounded outer corners. The upper surface of the disc is a plain grayish or brownish in color, and covered by small, flattened dermal denticles. The tubemouth whipray is relatively common at present, but is heavily pressured by habitat degradation and coastal fisheries. The International Union for Conservation of Nature (IUCN) has listed it as Vulnerable.

The Hortle's whipray is a little-known species of stingray in the family Dasyatidae, occurring in shallow estuaries and mud flats off southern New Guinea. This species, growing to 71 cm (28 in) across, has a heart-shaped pectoral fin disc with a long, pointed snout and minute eyes. It has a wide dorsal band of dermal denticles extending from in front of the eyes to the tail, as well as scattered sharp denticles on the snout. The underside of the disc is a distinctive bright yellow in color, sometimes with darker markings around the nostrils, mouth, and gill slits. The Hortle's whipray is threatened by extensive seine fisheries and habitat degradation, leading the International Union for Conservation of Nature (IUCN) to assess it as Near Threatened.

<span class="mw-page-title-main">Brown whipray</span> Species of cartilaginous fish

The brown whipray is a species of stingray in the family Dasyatidae, common in inshore, muddy habitats along the northern coast of Australia. It has often been confused in literature for the honeycomb stingray and the black-spotted whipray, which until recently was thought to be the same species. This species has an angular, diamond-shaped pectoral fin disc and a long, very thin tail without fin folds. It is plain brown above, sometimes with white dots or flecks near the edge of the disc, and white below; the tail is dark all over, with alternating dark and light bands near the tip. The maximum recorded disc width is 74 cm (29 in).

<span class="mw-page-title-main">Blackedge whipray</span> Species of cartilaginous fish

The blackedge whipray is a little-known species of stingray in the family Dasyatidae, found in the coastal waters of the Bay of Bengal and the Gulf of Mannar. Attaining a disc width of 1.8 m (5.9 ft), this species has a diamond-shaped disc with two small concavities on either side of the snout tip, and a long, whip-like tail without tail folds. It is characterized by large thorns with star-shaped bases scattered over the disc, and by the wide, black marginal bands on the underside of the disc. The International Union for Conservation of Nature (IUCN) currently lacks sufficient data to assess the blackedge whipray beyond Data Deficient.

<span class="mw-page-title-main">Leopard whipray</span> Species of cartilaginous fish

The leopard whipray is a little-known species of stingray in the family Dasyatidae, found in the Indian and Pacific Oceans from the Andaman Sea to the Coral Triangle. It is found close to shore at depths shallower than 70 m (230 ft), over soft substrates. Attaining a width of 1.8 m (5.9 ft), this species has a diamond-shaped pectoral fin disc with a pointed snout and an extremely long, whip-like tail without fin folds. Adult rays have a leopard-like dorsal pattern of dark brown rings on a yellowish brown background, as well as a row of enlarged, heart-shaped dermal denticles along the midline of the disc. Newborns and small juveniles have large, solid dark spots and few denticles. The leopard whipray is caught by fisheries in many parts of its range, primarily for meat.

<span class="mw-page-title-main">Honeycomb whipray</span> Species of cartilaginous fish

The honeycomb whipray is a species of stingray in the family Dasyatidae, found widely in the shallow coastal waters of the Indo-Pacific from India to the Malay Archipelago. This large species grows to 1.3 m (4.3 ft) across and has a diamond-shaped disc with rounded corners and a projecting, pointed snout. Its tail is long and whip-like, without fin folds. Adults have a striking dorsal color pattern consisting of large, dark brown rings and reticulations delineated by thin yellow lines, while juveniles have a pattern of large dark spots. This ray can also be distinguished from its similar relatives by an enlarged, pearl-like dermal denticle at the center of the back, which is followed by a few thorns. The International Union for Conservation of Nature (IUCN) has assessed the honeycomb whipray as endangered, as it faces heavy fishing pressure and habitat degradation across much of its range.

<span class="mw-page-title-main">Mumburarr whipray</span> Species of fish (stingray)

The mumburarr whipray is a species of whipray from northern Australia and southern Papua New Guinea, described in 2016.

References

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  3. 1 2 3 4 Last, P.R.; Compagno, L.J.V. (1999). "Myliobatiformes: Dasyatidae". In Carpenter, K.E.; Niem, V.H. (eds.). FAO identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Food and Agriculture Organization of the United Nations. pp. 1479–1505. ISBN   978-92-5-104302-8.
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  5. 1 2 Last, P.R.; Manjaji-Matsumoto, B.M. (2008). "Himantura dalyensis sp. nov., a new estuarine whipray (Myliobatoidei: Dasyatidae) from northern Australia". In Last, P.R.; White, W.T.; Pogonoski, J.J. (eds.). Descriptions of new Australian Chondrichthyans. CSIRO Marine and Atmospheric Research. pp. 283–291. ISBN   978-0-1921424-1-2.
  6. 1 2 3 Froese, Rainer; Pauly, Daniel (eds.) (2018). "Urogymnus polylepis" in FishBase. October 2018 version.
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  8. ↑ Naylor, G.J.P. (1992). "The phylogenetic relationships among requiem and hammerhead sharks: inferring phylogeny when thousands of equally most parsimonious trees result" (PDF). Cladistics. 8 (4): 295–318. doi:10.1111/j.1096-0031.1992.tb00073.x. hdl: 2027.42/73088 . PMID   34929961. S2CID   39697113.
  9. 1 2 3 4 5 6 Lovgren, S. (2008). "Giant River Stingrays Found Near Thai City". National Geographic News. National Geographic Society. Archived from the original on May 1, 2008. Retrieved December 20, 2013.
  10. 1 2 3 4 Last, P.R.; White, W.T.; Caire, J.N.; Dharmadi; Fahmi; Jensen, K.; Lim, A.P.F.; Manjaji-Matsumoto, B.M.; Naylor, G.J.P.; Pogonoski, J.J.; Stevens, J.D.; Yearsley, G.K. (2010). Sharks and Rays of Borneo. CSIRO Publishing. pp. 208–209. ISBN   978-1-921605-59-8.
  11. ↑ Tsoi, Grace (20 June 2022). "World's largest freshwater fish found in Mekong, scientists say". BBC News . Retrieved 20 June 2022.
  12. ↑ Michael I. Grant; Anthony W. J. Bicknell; Thaung Htut; Antt Maung; Thu Maung; Khin Myo Myo; Thu Rein; Min Khan San; William T. White; Kyaw Zay Ya; Meira Mizrahi (2022). "Market surveys and social media provide confirmation of the endangered giant freshwater whipray Urogymnus polylepis in Myanmar". Fish Biology. doi:10.1111/jfb.15073. PMC   9543834 .
  13. ↑ "Himantura chaophraya (Freshwater whipray)".
  14. ↑ Fyler, C.A.; Caira, J.N. (2006). "Five new species of Acanthobothrium (Tetraphyllidea: Onchobothriidae) from the freshwater stingray Himantura chaophraya (Batoidea: Dasyatidae) in Malaysian Borneo". Journal of Parasitology. 92 (1): 105–125. doi:10.1645/GE-3522.1. PMID   16629324. S2CID   24074236.
  15. ↑ Healy, C.J. (2006). "Three new species of Rhinebothrium (Cestoda: Tetraphyllidea) from the freshwater whipray, Himantura chaophraya, in Malaysian Borneo". Journal of Parasitology. 92 (2): 364–374. doi:10.1645/GE-560R.1. PMID   16729696. S2CID   1002099.
  16. 1 2 3 4 Fowler, S.L.; Cavanagh, R.D. (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. IUCN. pp. 348–349. ISBN   978-2-8317-0700-6.
  17. ↑ Compagno, L.J.V.; Cook, S.F. (2000). "Urogymnus polylepis Thailand subpopulation". IUCN Red List of Threatened Species . 2000: e.T39408A10228071. doi: 10.2305/IUCN.UK.2000.RLTS.T39408A10228071.en . Retrieved 13 November 2021.

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