Overview

Comprehensive Description

Biology

Inhabits sandy bottoms in estuaries and rivers (Ref. 12693). Feeds on bottom-dwelling crustaceans and shellfish. Breeds in fresh water (Ref. 32457). Ovoviviparous (Ref. 50449). Wounds caused by the dorsal spines are extremely painful and can be fatal. Sold fresh for human consumption (Ref. 32457). Total length maybe greater than 200 cm.
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Distribution

Range Description

This is a freshwater species, occurring in the rivers of Southeast Asia. It is known from the Kapuas River in western Kalimantan and Indragiri River, Sumatra, Indonesia; Perak River, western Peninsular Malaysia; and Chao Phrya River, Thailand (Taniuchi 1979, Compagno and Roberts 1982).

Subpopulation details are unknown. If, as seems likely, this ray is unable to transit marine habitats, each riverine population will be completely isolated.
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Asia: Indonesia, Malaysia and Thailand (Chao Phraya, Mekong and Tapi Rivers).
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Asia.
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Physical Description

Size

Maximum size: 600 mm WD
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Max. size

60.0 cm WD (male/unsexed; (Ref. 7050))
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Diagnostic Description

Narrow white marginal band around disk; white spot anterior to spiracle and posterior to eye; ventral surface plain; spiral valve with 11-14 turns (Ref. 12693).
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Type Information

Paratype for Himantura signifer
Catalog Number: USNM 229492
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Fishes
Preparation: Unknown; Radiograph
Collector(s): T. Roberts
Year Collected: 1976
Locality: Indonesia: Kalimantan Barat, Sintang Market, Indonesia, Pacific
  • Paratype:
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This rarely recorded freshwater species is known from about 10 specimens in museum collections, mostly from the Kapuas River, Kalimantan. No information is available on any of this species? life history parameters.

Systems
  • Freshwater
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Environment

benthopelagic; freshwater; brackish
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Life History and Behavior

Life Cycle

Exhibit ovoviparity (aplacental viviparity), with embryos feeding initially on yolk, then receiving additional nourishment from the mother by indirect absorption of uterine fluid enriched with mucus, fat or protein through specialised structures (Ref. 50449). Distinct pairing with embrace (Ref. 205). Distinct pairing with embrace (Ref. 205).
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
B1ab(iii)

Version
3.1

Year Assessed
2005

Assessor/s
Compagno, L.J.V.

Reviewer/s
Musick, J.A. & Fowler, S.L. (Shark Red List Authority)

Contributor/s

Justification
This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).

The White-edge Freshwater Whipray (Himantura signifer) is a very rare freshwater ray known from only a few specimens and four riverine systems (although it may also be present but unrecorded in other rivers). It is confined to tropical freshwater habitats that are under intensive threat from fisheries, pollution, logging in the catchment areas and river engineering projects.

History
  • 2000
    Endangered
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Population

Population
Rare.

Population Trend
Unknown
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Threats

Major Threats
This rare ray is taken infrequently as bycatch in freshwater teleost fisheries, which are intensive through much of its range. It is possibly taken for the aquarium trade (unverified). It lives in areas where riverine pollution and habitat degradation are continuing apace. Populations (which are probably isolated in each river where it occurs) are likely to be under serious continued threat as a result of logging activities and pollution from agricultural chemicals, sewage and industrial waste in the river catchments and loss of habitat due to dam construction (e.g., Chao Phraya River). Habitat loss and degradation are likely a major impact on the species.
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Endangered (EN) (B1ab(iii))
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Management

Conservation Actions

Conservation Actions
The Thai government started a project in the 1990s to breed this and other freshwater stingrays in captivity at Chai Nat above the dam on the Chao Phraya River to counter declines of freshwater rays in the river. Two specimens of what was possibly this species (or a closely related species) were seen in captivity here in 1993. We later (1996) learned that the project had been put on hold, at least temporarily.
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: minor commercial; aquarium: commercial
  • Wongrat, P. 1998 Whip-tailed freshwater stingrays family Dasyatidae of Thailand. p. 35-40. In Adaptability and conservation of freshwater elasmobranchs. Report of Research Project, Grant-in-Aid for International Scientific Research (Field Research) in the financial year of 1996 and 1997. 119 p. (Ref. 32457)   http://www.fishbase.org/references/FBRefSummary.php?id=32457&speccode=15389 External link.
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Wikipedia

White-edge freshwater whipray

The white-edge freshwater whipray (Himantura signifer) 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.

Taxonomy and phylogeny[edit]

The white-edge freshwater whipray was described by Leonard Compagno and Tyson Roberts in a 1982 issue of Environmental Biology of Fishes, with the specific epithet signifer (Latin for "sign-bearing") in reference to its distinctive coloration. The type specimen is an immature female 29 cm (11 in) across, collected from the mouth of the Sungai Ketungau off the Kapuas River in West Kalimantan, Indonesia.[2] Other common names for this species include freshwater stingray, pale whipray, and white-rimmed stingray.[3] Within its genus, the white-edge freshwater whipway most closely resembles H. kittipongi, described in 2005.[4] A 1999 phylogenetic analysis, based on cytochrome b sequences, found that it is closely related to H. gerrardi and H. imbricata, which form a sister species pair.[5]

Distribution and habitat[edit]

One of the few members of its family that seems to exclusively inhabit fresh water, the white-edge freshwater whipray is known from four Southeast Asian river systems: the Kapuas River in Borneo, the Indragiri River in Sumatra, the Perak River in Peninsular Malaysia, and the Chao Phraya River in Thailand.[1] Although these rivers are now isolated from one another, when sea levels were low during the Pleistocene epoch (2.6 million to 12,000 years ago) they may have all been contiguous as part of the Central or North Sundaland drainage basin. At that time, this ray could have dispersed into its present range without having to enter salt water.[2] This bottom-dwelling species favors a sandy habitat.[3]

Description[edit]

The white-edge freshwater whipray has a thin and oval pectoral fin disc slightly wider than long. The anterior margins of the disc converge with a broad angle at the tip of the snout, which is slightly protruding. The eyes are small and immediately followed by much larger spiracles. There is a flap of skin between the nares with a fringed, subtly concave or three-lobed posterior margin. The mouth is gently bow-shaped, with a groove running from the nasal flap around its corners. There are 38–45 upper tooth rows and 37–46 lower tooth rows; the teeth are well-spaced and arranged in a quincunx pattern. Each tooth has a blunt conical crown with a transverse cutting edge; this edge is higher and serrated in males and lower and blunt in females. There is a row of 4–5 papillae across the floor of the mouth: a large inner pair, a smaller outer pair, and sometimes a central one of varying size.[2]

The tail is about 3.5 times as long as the disc and bears two stinging spines on top; behind the spines the tail becomes slender and whip-like, without any fin folds.[2] Two recorded individuals had tail spines 86 and 87 mm (3.4 and 3.4 in) long with 70 and 89 serrations respectively.[6] A band of skin running along the back from between the eyes to the tail base is roughened by small, flattened heart-shaped dermal denticles interspersed with small conical denticles. There are more denticles on the tail behind the spines, and small individuals also have a pearl spine in the center of the disc.[2] The disc is brown above, with mottling in the center and on the tail base, a white spot between the eye and spiracle, and a sharp white band running around its periphery. The underside is completely white, as is the tail behind the spines. This ray grows up to 60 cm (24 in) across and perhaps over 2 m (6.6 ft) long.[3][7]

Biology and ecology[edit]

Like the other freshwater and euryhaline members of its family, but unlike the specialized South American river stingrays of the family Potamotrygonidae, the white-edge freshwater whipray retains the ability to synthesize urea for osmoregulation and can survive in brackish water with a salinity of 20 ppt for at least two weeks.[8] Indeed, this ray might experience greater salinity-induced oxidative stress in freshwater than in brackish water, possibly related to its short history of freshwater invasion. [9] To this end, it has been suggested that there may be a possible relationship between the successful invasion of the freshwater environment by some euryhaline marine elasmobranchs and the ability of these elasmobranchs to increase the capacity of ascorbic acid synthesis to defend against hyposalinity stress. In addition, the ampullae of Lorenzini of H. signifer are intermediate in size and structure between the large, complex ampullae of its marine relatives and the small, simple ampullae of potamotrygonid stingrays, which may be a consequence of varying salinities in its environment and demands that would place on electroreception.[10] The white-edge freshwater whipray feeds mainly on small benthic organisms, including crustaceans, molluscs, and insect larvae. Reproduction is aplacental viviparous with the developing embryos sustained by maternally produced histotroph ("uterine milk"), as is the case in other stingrays. Newborns measure 10–12 cm (3.9–4.7 in) across; males and females mature sexually at 21–23 cm (8.3–9.1 in) and 25–26 cm (9.8–10 in) across respectively.[11]

Human interactions[edit]

The venomous stings of the white-edge freshwater whipray are capable of inflicting excruciating and even fatal wounds on humans.[3] This species is extremely rare, with only about 10 specimens having been deposited in museum collections. Most of its range is subject to heavy fishing pressure; this ray is infrequently caught using fish traps, spears, and bottom-set lines; it is sold for meat and the aquarium trade.[1][11] Habitat loss and degradation as a result of pollution, logging and dam construction are likely to pose an even a greater threat to the survival of this species. In Thailand, dams built on the Chao Phraya have fragmented the resident stingray population and effectively reduced its genetic diversity.[7] Because of diverse threats faced by this ray and the lack of exchange between the different rivers it inhabits, the International Union for Conservation of Nature (IUCN) has assessed the white-edge freshwater whipray as Endangered. The Thai government began a captive breeding program for this and other endangered freshwater stingrays at Chai Nat during the 1990s, but by 1996 the program had been placed on hold.[1]

References[edit]

  1. ^ a b c d Compagno, L.J.V. (2005). Himantura signifer. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved January 11, 2010.
  2. ^ a b c d e Compagno, L.J.V. and T.R. Roberts (1982). "Freshwater stingrays (Dasyatidae) of Southeast Asia and New Guinea, with description of a new species of Himantura and reports of unidentified species". Environmental Biology of Fishes 7 (4): 321–339. doi:10.1007/BF00005567. 
  3. ^ a b c d Froese, Rainer and Pauly, Daniel, eds. (2010). "Himantura signifer" in FishBase. January 2010 version.
  4. ^ Vidthayanon, C. and T.R. Roberts (2005). "Himantura kittipongi, a new species of freshwater whiptail stingray from the Maekhlong River of Thailand (Elasmobranchii, Dasyatididae)". Natural History Bulletin of the Siam Society 53 (1): 123–132. 
  5. ^ Sezaki, K., R.A. Begum, P. Wongrat, M.P. Srivastava, S. SriKantha, K. Kikuchi, H. Ishihara, S. Tanaka, T. Taniuchi and S. Watabe (1999). "Molecular Phylogeny of Asian Freshwater and Marine Stingrays Based on the DNA Nucleotide and Deduced Amino Acid Sequences of the Cytochrome b Gene". Fisheries Science 65 (4): 563–570. 
  6. ^ Cuny, G. and C. Piyapong (March 2007). "Tail spine characteristics of stingrays (order Myliobatiformes): a comment to Schwartz (2005)". Electronic Journal of Ichthyology 3 (1): 15–17. 
  7. ^ a b Fowler, S.L., R.D. Cavanagh, M. Camhi, G.H. Burgess, G.M. Cailliet, S.V. Fordham, C.A. Simpfendorfer, and J.A. Musick (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. International Union for Conservation of Nature and Natural Resources. pp. 351–352. ISBN 2-8317-0700-5. 
  8. ^ Tam, W.L., W.P. Wong, A.M. Loong, K.C. Hiong, S.F. Chew, J.S. Ballantyne and Y.K. Ip (September 2003). "The osmotic response of the Asian freshwater stingray (Himantura signifer) to increased salinity: a comparison with marine (Taeniura lymma) and Amazonian freshwater (Potamotrygon motoro) stingrays". Journal of Experimental Biology 206 (17): 2931–2940. doi:10.1242/jeb.00510. 
  9. ^ Wong, S.Z.H., B. Ching, Y.R. Chng, W.P. Wong, S.F. Chew and Y.K. Ip (June 2013). "Ascorbic Acid Biosynthesis and Brackish Water Acclimation in the Euryhaline Freshwater White-Rimmed Stingray, Himantura signifer". PloS One 8 (6): e66691. doi:10.1371/journal.pone.0066691. 
  10. ^ Raschi, W., E.D. Keithan, and W.C.H. Rhee (February 18, 1997). "Anatomy of the Ampullary Electroreceptor in the Freshwater Stingray, Himantura signifer". Copeia 1997 (1): 101–107. 
  11. ^ a b Sharks and Rays of Borneo. CSIRO Publishing. 2010. pp. 210–211. ISBN 978-1-921605-59-8. 
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