Bluespotted ribbontail ray
The bluespotted ribbontail ray, Taeniura lymma, is a species of stingray in the family Dasyatidae, common throughout the coral reefs of the tropical Indian and western Pacific Oceans. A fairly small species not exceeding 35 cm (14 in) in width, this ray is easily recognizable by its oval pectoral fin disk, relatively short and thick tail with a deep fin fold underneath, and striking color pattern of many electric blue spots on a yellowish background with a pair of blue stripes on the tail.
Found from the intertidal zone to a depth of 30 m (98 ft), at night small groups of bluespotted ribbontail rays follow the rising tide onto sandy flats to hunt small benthic invertebrates and bony fishes. When the tide recedes, the rays separate and withdraw to shelters on the reef. Reproduction is aplacental viviparous, with females giving birth to litters of up to 7 young. This ray is capable of injuring humans with its venomous tail spines, though it prefers to flee if threatened. Because of its beauty and size, the bluespotted ribbontail ray is popular with private aquarists despite adapting poorly to captivity. The International Union for Conservation of Nature (IUCN) has listed this species as Near Threatened; it faces widespread habitat degradation and intensive fishing throughout its range.
Taxonomy and phylogeny
The bluespotted ribbontail ray was originally described as Raja lymma by Swedish naturalist Peter Forsskål, in his 1775 Descriptiones Animalium quae in itinere ad maris australis terras per annos 1772, 1773, et 1774 suscepto collegit, observavit, et delineavit Joannes Reinlioldus Forster, etc., curante Henrico Lichtenstein. The specific epithet lymma means "dirt". Subsequent authors placed this species in the genus Taeniura. Forsskål did not designate a type specimen.
Other common names for this species include bluespotted ray, stingray, lagoon ray, or fantail ray, (lesser) fantail ray, lagoon ray, reef ray, and ribbontail or ribbon-tailed stingray. Morphological examination suggests that the bluespotted ribbontail ray may be more closely related to the South American river stingrays (Potamotrygonidae) than to the congeneric blotched fantail ray (T. meyeni).
Distribution and habitat
Widespread in the nearshore waters of the tropical Indo-Pacific region, the bluespotted ribbontail ray has a range that extends around the periphery of the Indian Ocean from South Africa to the Arabian Peninsula to Southeast Asia, including Madagascar, Mauritius, Zanzibar, the Seychelles, Sri Lanka, and the Maldives. It is rare in the Persian Gulf and Gulf of Oman. In the Pacific Ocean, this species is found from the Philippines to northern Australia, as well as around numerous Melanesian and Polynesian islands as far east as the Solomon Islands.
Rarely found deeper than 30 m (98 ft), the bluespotted ribbontail ray frequents sandy areas near coral reefs; it is also common in the intertidal zone and tidal pools, and has been observed near seagrass beds. Considerable numbers of bluespotted ribbontail rays appear seasonally off South Africa in the summer.
The pectoral fin disk of the bluespotted ribbontail ray is oval in shape, around four-fifths as wide as long, with a rounded to broadly angular snout. The large, protruding eyes are immediately followed by the broad spiracles. There is a narrow flap of skin between the nares with a fringed posterior margin, reaching past the mouth. The lower jaw dips at the middle and deep furrows are present at the mouth corners. There are 15–24 tooth rows in either jaw, arranged into pavement-like plates, and two large papillae on the floor of the mouth. The pelvic fins are narrow and angular. The thick, depressed tail measures about 1.5 times the disk length and bears 1–2 (usually 2) serrated spines well behind the tail base; there is a deep fin fold on the ventral surface, reaching the tip of the tail, and a low midline ridge on the upper surface.
The skin is generally smooth, save for perhaps a scattering of small thorns on the middle of the back. The dorsal coloration is striking, consisting of numerous circular, neon blue spots on a yellowish brown or green background; the spots vary in size, becoming smaller and denser towards the disk margin. The tail has two stripes of the same blue running along each side as far as the spines. The eyes are bright yellow and the belly is white. Individuals found off southern Africa may lack the blue tail stripes. The bluespotted ribbontail ray grows to 35 cm (14 in) across, 80 cm (31 in) long, and 5 kg (11 lb).
Biology and ecology
One of the most abundant stingrays inhabiting Indo-Pacific reefs, the bluespotted ribbontail ray spends the day hidden inside caves or under ledges, often with only its tail showing. At night, small groups assemble and swim onto shallow sandy flats with the rising tide to feed. Unlike many other stingrays, this species seldom buries itself in sand. The bluespotted ribbontail ray excavates sand pits in search of molluscs, polychaete worms, shrimps, crabs, and small benthic fishes; when prey is located, it is trapped by the body of the ray and maneuvered into the mouth with the disk. Other fishes, such as goatfish, frequently follow foraging rays, seeking food missed by the ray.
Breeding in the bluespotted ribbontail ray occurs during late spring and summer; the male chases the female and nips at her disk, eventually biting and holding onto her for copulation. Like other stingrays, this species is aplacental viviparous, with the developing embryos sustained by yolk and later "uterine milk", containing mucus, fat, and proteins, produced by their mother. The gestation period may be 4–12 months. Females bear litters of up to 7 young, each measuring around 9 cm (3.5 in) long and resembling a miniature version of the adult.
Known predators of the bluespotted ribbontail ray include hammerhead sharks and bottlenose dolphins (Tursiops sp.); other large fishes and marine mammals may also be potential predators. When threatened, this ray flees at high speed in a zigzag pattern, to throw off pursuers. Numerous parasites have been identified from this ray: the tapeworms Aberrapex manjajiae, Anthobothrium taeniuri, Cephalobothrium taeniurai, Echinobothrium elegans and E. helmymohamedi, Kotorelliella jonesi, Polypocephalus saoudi, and Rhinebothrium ghardaguensis and R. taeniuri, the monogeneans Decacotyle lymmae, Empruthotrema quindecima, Entobdella australis, and Pseudohexabothrium taeniurae, the flatworms Pedunculacetabulum ghardaguensis and Anaporrhutum albidum, the nematode Mawsonascaris australis, the copepod Sheina orri, and the protozoan Trypanosoma taeniurae. This species has been observed soliciting cleanings from the bluestreak cleaner wrasse (Labroides dimidiatus) by raising the margins of its disk and its pelvic fins.
While timid and innocuous towards humans, the bluespotted ribbontail ray is capable of inflicting an excruciating wound with its venomous tail spines. Its attractive appearance and relatively small size has resulted in this ray being the most common stingray found in the home aquarium trade. However, it seldom fares well in captivity and very few hobbyists are able to maintain one for long. Many specimens refuse to feed in the aquarium, while even seemingly healthy individuals often inexplicably die or stop feeding. This species is also utilized as food in East Africa and Australia; it is captured intentionally or incidentally using gillnets, longlines, spears, and fence traps.
The International Union for Conservation of Nature (IUCN) has assessed the bluespotted ribbontail ray as Near Threatened. Although still relatively common and widely distributed, this species faces continuing degradation of its coral reef habitat throughout its range, from development and destructive fishing practices using cyanide or dynamite. In addition, its populations are under heavy pressure by artisanal and commercial fisheries, and by local collecting for the aquarium trade.
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