Black-spotted whipray

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Black-spotted whipray
Stingray shark bay.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: Maculabatis
Species:
M. astra
Binomial name
Maculabatis astra
Himantura astra rangemap.png
Range of the black-spotted whipray
Synonyms
  • Himantura astraLast, Manjaji-Matsumoto & Pogonoski, 2008

The black-spotted whipray (Maculabatis astra) is a species of stingray in the family Dasyatidae, found in the coastal waters off southern New Guinea and northern Australia. Long thought to be a variant of the related brown whipray (H. toshi), this species has an angular, diamond-shaped pectoral fin disc and a whip-like tail without fin folds. It is characterized by its dorsal color pattern, which consists of a variably extensive covering of small, close-set dark, and sometimes also white spots, on a grayish-brown background. In addition, the tail has alternating light and dark saddles past the stinging spine. This species reaches a maximum recorded width of 80 cm (31 in).

Contents

Crustaceans are the main type of food consumed by the black-spotted whipray. It is aplacental viviparous, with females gestating 13 young at a time, supplying them with histotroph ("uterine milk"). Most of the black-spotted whipray's range lies within Australian waters, where it faces minimal conservation threats since the widespread deployment of bycatch-reducing measures on commercial trawlers. It is caught in small numbers for meat, skin, and cartilage by Indonesian fishers, as well as by prawn seine fishers off Papua New Guinea. A 2004 assessment of the brown whipray by the International Union for Conservation of Nature (IUCN), which also included data on the black-spotted whipray, listed them under Least Concern.

Taxonomy

The black-spotted whipray was traditionally thought to be the same species as the brown whipray (H. toshi). [2] In 1994, Commonwealth Scientific and Industrial Research Organisation (CSIRO) researchers Peter Last and John Stevens tentatively identified a spotted variant of H. toshi as "Himantura sp. A". However, it was not until more specimens became available for study in the mid-2000s that the black-spotted whipray was confirmed as distinct, albeit closely related, species to H. toshi. Last, Mabel Manjaji-Matsumoto, and John Pogonoski formally described it in a 2008 CSIRO publication, giving it the specific epithet astra after the Latin astrum ("constellation"). The type specimen is an adult male 59 cm (23 in) across, collected from the Gulf of Carpentaria. [2] Like T. toshi, this species belongs to the 'uarnak' species complex, which also contains H. fai , H. gerrardi , H. jenkinsii , H. leoparda , H. uarnak , and H. undulata . Other common names for the black-spotted whipray include coachwhip ray, Tosh's longtail ray, and wulura. [3]

Description

The black-spotted whipray has black spots on its disc and alternating dark and light saddles on its tail. Himantura astra csiro-nfc.jpg
The black-spotted whipray has black spots on its disc and alternating dark and light saddles on its tail.

The black-spotted whipray can grow to 80 cm (31 in) across and 1.8 m (5.9 ft) long; reports of rays 1 m (3.3 ft) or more across are likely in error. It has a diamond-shaped, relatively thin pectoral fin disc approximately 1.11.2 times wider than long. The outer corners of the disc are fairly angular, and the leading margins are nearly straight. The snout is triangular and forms a broadly obtuse angle with a barely protruding, pointed tip. The eyes are small and immediately followed by larger, oval spiracles. The long, slender nostrils have a short, skirt-shaped curtain of skin between them; the posterior margin of the curtain is concave on either side and finely fringed. The mouth is strongly bow-shaped and contains a row of four papillae (nipple-like structures) across the floor. The small, blunt teeth number 4149 rows in the upper jaw and 4050 rows in the lower jaw. [2] [3]

The pelvic fins are small and somewhat narrow, with a curving posterior margin; males have stout claspers. The very thin, gently tapering whip-like tail measures 2.12.7 times as long as the disc is wide, and lacks fin folds. One or two slender stinging spines are present atop the tail; many individuals have the sting missing. Behind the sting, there is a deep ventral groove and prominent lateral ridges running to the tip of the tail. The upper surface of the disc is densely covered by tiny heart-shaped dermal denticles in a wide central band from between the eyes to entirely cover the tail, with those at the center of the disc are slightly larger and spear-shaped. Newborns lack denticles; the denticles on the "shoulders" and head are the first to develop. This species is grayish brown above, with many small dark spots covering all or part of the disc and tail base; sometimes there are also subtle to prominent white spots, that may be arranged into rosettes surrounding the dark spots or into indistinct rings ("pseudo-ocelli"). The tail past the sting bears alternating light and dark saddles; these form complete bands in juveniles under 50 cm (20 in) across. The spots of rays under 30 cm (12 in) across are proportionately larger and widely spaced. The upper half of the eyeball is spotted while the lower half is white. The disc and tail are plain white beneath. [2] [3]

Distribution and habitat

The black-spotted whipray is found widely off northern Australia from Shark Bay in Western Australia and Moreton Bay in Queensland, including the Timor Sea, and is particularly abundant in the Gulf of Carpentaria. It has also been reported from off southern New Guinea. This bottom-dwelling species inhabits coastal waters 1–141 m (3.3–462.6 ft) deep, favoring sandy habitats, and tends to be found farther from shore than the brown whipray. In Shark Bay, it is found in greater numbers during the warm season than the cold. [3] [4]

Biology and ecology

Over 90% of the black-spotted whipray's diet consists of crustaceans. [5] In the Gulf of Carpentaria, it is a major predator of penaeid prawns, which constitute over half of its diet. [6] Shrimp are the predominant prey of young rays under 23 cm (9.1 in) across, while stomatopods and crabs become more important with age. For rays off Queensland and in the Torres Strait, polychaete worms constitute an important secondary food source to crustaceans. [5] This species has also been known to take bony fishes. [3] Like other stingrays, the black-spotted whipray is aplacental viviparous, with females nourishing their young with nutrient-rich histotroph ("uterine milk"). Females have a single functionary ovary and uterus (on the left), and produce litters of 13 pups. The newborns measure 17–19 cm (6.7–7.5 in) across; both sexes mature at about 46–50 cm (18–20 in) across. The growth rate is relatively low, with females growing much more slowly than males. [3] [5]

Human interactions

The International Union for Conservation of Nature's (IUCN) 2004 assessment of the brown whipray (which at the time also included the black-spotted whipray), listed it under Least Concern. Their range off northern Australia was noted to be large and relatively protected from fishing pressure, as the mandatory implementation of Turtle Exclusion Devices (TEDs) on bottom trawls has greatly reduced bycatch mortality. [7] In IndonHimanturaesian waters, small numbers of black-spotted whiprays are caught and marketed for their skin, which is extremely valuable, and also meat and cartilage. [3] Off Papua New Guinea, juveniles are an infrequent, incidental catch of seine net fishers targeting penaeid prawns. [7]

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<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">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">Peppered maskray</span> Species of cartilaginous fish

The peppered maskray or speckled maskray, is a species of stingray in the family Dasyatidae, found in shallow waters off northeastern Australia. This small, thin-bodied ray attains a maximum width of 32 cm (13 in). It has a diamond-shaped pectoral fin disc with a row of tiny thorns along the midline, and a relatively short, whip-like tail with both upper and lower fin folds. Its upper surface has a speckled color pattern consisting of black spots and brownish reticulations on a light yellow to brown background.

References

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  2. 1 2 3 4 Last, P.R.; B.M. Manjaji-Matsumoto & J.J. Pogonski (2008). "Himantura astra sp. nov., a new whipray (Myliobatoidei: Dasyatidae) from northern Australia". In Last, P.R.; W.T. White & J.J. Pogonoski (eds.). Descriptions of new Australian Chondrichthyans. CSIRO Marine and Atmospheric Research. pp. 303–314. ISBN   978-0-1921424-1-2. (corrected) ISBN   1-921424-18-2 (invalid, listed in publication).
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  5. 1 2 3 Jacobsen, I. (200710). Biology of Five Benthic Elasmobranch Species from Northern and North-eastern Australia, Including a Taxonomic Review of Indo-West Pacific Gymnuridae. PhD Thesis, School of Biomedical Sciences, The University of Queensland.
  6. Brewer, D.T.; S.J.M. Blaber & J.P. Salini (1991). "Predation on penaeid prawns by fishes in Albatross Bay, Gulf of Carpentaria". Marine Biology. 109 (2): 231–240. Bibcode:1991MarBi.109..231B. doi:10.1007/BF01319391. S2CID   84359435.
  7. 1 2 Rigby, C.; Pierce, S.J. (2016). "Maculabatis toshi". IUCN Red List of Threatened Species . 2016: e.T161505A104194858. doi: 10.2305/IUCN.UK.2016-3.RLTS.T161505A104194858.en . Retrieved 13 November 2021.