Thorntail stingray

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Thorntail stingray
Thorntail stingray new zealand2.jpg
Scientific classification
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D. thetidis
Binomial name
Dasyatis thetidis
Dasyatis thetidis rangemap.png
Range of the thorntail stingray [2]
Synonyms

Dasyatis lubricusSmith, 1957
Dasybatus agulhensisBarnard, 1925

Contents

The thorntail stingray, black stingray, or longtail stingray (Dasyatis thetidis) is a species of stingray in the family Dasyatidae. It is found off southern Africa, Australia, and New Zealand from the intertidal zone to a depth of 440 m (1,440 ft). This bottom-dweller inhabits soft-bottomed habitats such as lagoons, estuaries, and reefs. Growing to 1.8 m (5.9 ft) across and over 200 kg (440 lb) in weight, the thorntail stingray is among the largest stingrays in the world. Uniformly dark above and light below, it has a diamond-shaped pectoral fin disc and a very long, whip-like tail with a fin fold underneath. The upper surface of the disc and the tail bear numerous stout, sharp thorns.

The diet of the thorntail stingray consists of benthic invertebrates and bony fishes. It has been known to gather in large groups during summertime. Like other stingrays, it is aplacental viviparous, with the developing embryos sustained to term by histotroph ("uterine milk") produced by the mother. The venomous stinging spine of the thorntail stingray can inflict a painful injury, though it is not aggressive towards humans. It is caught by commercial and recreational fishers, though the impact of such activities on its population is unknown. As a result, the International Union for Conservation of Nature (IUCN) has listed this species as Data Deficient. A Thorntail stingray with a width of 1.67m and length of 2.35m was caught and released of Warner Beach, South Africa in Jan 2020.

Taxonomy

A thorntail stingray at Green Island, New South Wales. Dasyatis thetidis.jpg
A thorntail stingray at Green Island, New South Wales.

Australian ichthyologist James Douglas Ogilby originally described the thorntail stingray from four specimens collected off New South Wales during the 1898 scientific expedition of the trawler HMCS Thetis, after which the species was named. His account was published a year later in the scientific journal Memoirs of the Australian Museum. [3] Other common names for this species include black skate, black stingaree, long-tailed stingaree, longtail black stingray, thorn stingray, and thorntail ray. [4]

Distribution and habitat

The thorntail stingray is found off southern Africa from Algoa Bay, South Africa to Barra da Falsa, Mozambique and Réunion, as well as off Australia from Shark Bay to northern New South Wales, Lord Howe Island, Norfolk Island, and New Zealand. [5] [6] It is fairly common off Australia and New Zealand and less so elsewhere. [1] [7] Favoring inshore habitats with soft bottoms, this benthic species is commonly encountered in estuaries and lagoons, around rocky and coral reefs, and over reef flats. In Australia, it has been known to swim up rivers. Off New Zealand, large groups of thorntail stingrays have been seen inside caves and beneath rocky arches. This species is known to occur as deep as 440 m (1,440 ft). [1] [8]

Description

The presence of numerous thorns on the back and tail are a characteristic trait of the thorntail stingray. Thorntail stingray new zealand.jpg
The presence of numerous thorns on the back and tail are a characteristic trait of the thorntail stingray.

One of the largest members of its family, the thorntail stingray reaches at least 4 m (13 ft) long, 1.8 m (5.9 ft) across, and 214 kg (472 lb) in weight. This species has a diamond-shaped pectoral fin disc about one-fourth wider than long, with sinuous leading margins converging to a slightly protruding snout tip and rounded outer and trailing margins. The mouth is slightly arched; there are five papillae across the floor with the outermost pair smaller and set apart from the others. The tooth rows number 25–43 in the upper jaw and 29–48 in the lower jaw, and are arranged with a quincunx pattern into pavement-like surfaces. [3] [5]

The pelvic fins have rounded tips and gently curved trailing margins. [5] The whip-like tail measures about twice the length of the disc and bears one or two long stinging spines with up to 88 serrations. [9] A narrow fin fold runs beneath the tail and ends well before the tail tip. Large juveniles and adults have a row of large, sharp thorns running along the midline of the back from behind the eyes to the tail spine, and thorns of various sizes are also scattered about the dorsal surface of the disc. The tail behind the spine is densely covered by stout thorns. This species is a uniform dark brown or gray to black above and whitish below. [5] The longer tail, presence of thorns, and absence of white dots atop the disc differentiate this species from the short-tail stingray (D. brevicaudata), another giant stingray that shares its range. [7]

Biology and ecology

Thorntail stingrays often rest on the bottom during the day. Dasyatis thetidis 2.jpg
Thorntail stingrays often rest on the bottom during the day.

During the day, thorntail stingrays are often seen resting on patches of sand. [10] This species preys mainly upon crabs, mantis shrimp, bivalves, polychaete worms, and conger eels. [1] Off New Zealand, both it and the short-tail stingray regularly fall prey to local killer whales (Orcinus orca). [11] A known parasite of this species is the nematode Echinocephalus overstreeti. [12] Thorntail stingrays have been reported to congregate in warm, shallow waters during the summer, possibly for reproductive purposes. [8] This species is aplacental viviparous like other stingrays. [4]

Human interactions

The tail spine of the thorntail stingray is potentially injurious to humans. [4] It is reportedly unaggressive and approachable, and can be conditioned to accept being "ridden" by divers. [10] At Hamelin Bay, Western Australia, many thorntail stingrays, short-tail stingrays, and Australian bull rays (Myliobatis australis) regularly gather to be hand-fed fish scraps; the number of visitors has steadily increased in recent years, and there is interest in developing the site as a permanent tourist attraction. [13]

Thorntail stingrays are caught as bycatch in nets and on line gear, probably in low numbers. Most individuals landed are discarded, though the rate of survival after capture is unknown, as this species may be subject to persecution by fishery workers. Recreational anglers sometimes hook this ray, which may be difficult to bring in due to its size. At present, the International Union for Conservation of Nature (IUCN) lacks sufficient information to assess the thorntail stingray beyond Data Deficient. From 1986 to 1997, New Zealand reported an average annual catch of 15 tons for this species and the short-tail stingray combined, though this figure may underestimate the total fishery impact. [1] In June 2018 the New Zealand Department of Conservation classified the thorntail stingray as "Not Threatened" with the qualifier "Secure Overseas" under the New Zealand Threat Classification System. [14]

Related Research Articles

Short-tail stingray Dasyatis brevicaudata

The short-tail stingray or smooth stingray is a common species of stingray in the family Dasyatidae. It occurs off southern Africa, typically offshore at a depth of 180–480 m (590–1,570 ft), and off southern Australia and New Zealand, from the intertidal zone to a depth of 156 m (512 ft). It is mostly bottom-dwelling in nature and can be found across a range of habitats from estuaries to reefs, but also frequently will swim into open water. The largest stingray in the world, this heavy-bodied species can grow upwards of 2.1 m (6.9 ft) across and 350 kg (770 lb) in weight. Its plain-colored, diamond-shaped pectoral fin disc is characterized by a lack of dermal denticles even in adults, and white pores beside the head on either side. Its tail is usually shorter than the disc and thick at the base. It is armed with large tubercles and a midline row of large thorns in front of the stinging spine which has the dorsal and ventral fin folds behind.

Round ribbontail ray species of fish

The round ribbontail ray is a species of stingray in the family Dasyatidae, found throughout the nearshore waters of the tropical Indo-Pacific, as well as off islands in the eastern Pacific. It is a bottom-dwelling inhabitant of lagoons, estuaries, and reefs, generally at a depth of 20–60 m (66–197 ft). Reaching 1.8 m (5.9 ft) across, this large ray is characterized by a thick, rounded pectoral fin disc covered by small tubercles on top, and a relatively short tail bearing a deep ventral fin fold. In addition, it has a variable but distinctive light and dark mottled pattern on its upper surface, and a black tail.

Red stingray species of fish

The red stingray is a species of stingray in the family Dasyatidae, found in the northwestern Pacific Ocean off Japan, Korea, and China, and possibly elsewhere. It primarily inhabits shallow, sandy habitats close to shore, and has been known to enter brackish water. The red stingray has a diamond-shaped pectoral fin disc and gains its common name from its bright orange-red underside; there may also be patches of orange at various spots on its upper surface. Most individuals are no more than 1 m (3.3 ft) long.

Estuary stingray species of 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.

Longnose stingray species of fish

The longnose stingray is a species of stingray in the family Dasyatidae, native to the western Atlantic Ocean from the southern Gulf of Mexico to Brazil. Found in coastal waters no deeper than 36 m (118 ft), this demersal species favors muddy or sandy habitats. The longnose stingray is characterized by its angular, rhomboid pectoral fin disc, moderately projecting snout, and whip-like tail with a dorsal keel and ventral fin fold. It typically grows to 1.25 m (4.1 ft) across and is brownish above and light-colored below.

Mekong freshwater stingray species of 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.

The Brazilian large-eyed stingray, Dasyatis marianae, is a species of stingray in the family Dasyatidae. Endemic to northeastern Brazil, adults of this species inhabit shallow coral and sandstone reefs while the young are also found near beaches and in estuaries. This stingray measures up to 40 cm (16 in) across and can be identified by its large eyes, equally long fin folds above and below the tail, and distinctive coloration consisting of various dark brown markings on a yellowish-brown background above, and two pairs of dark brown blotches on a white background below. Reproduction is aplacental viviparous, with females giving birth to one young at a time, twice a year, and using sandbanks as nursery areas. The Brazilian large-eyed stingray is collected by artisanal fisheries and for the ornamental fish trade; the International Union for Conservation of Nature (IUCN) does not have sufficient data to assess its conservation status.

Bluntnose stingray species of fish

The bluntnose stingray or Say's stingray is a species of stingray in the family Dasyatidae, native to the coastal waters of the western Atlantic Ocean from the U.S. state of Massachusetts to Venezuela. It is a bottom-dwelling species that prefers sandy or muddy habitats 1–10 m (3.3–32.8 ft) deep, and is migratory in the northern portion of its range. Typically growing to 78 cm (31 in) across, the bluntnose stingray is characterized by a rhomboid pectoral fin disc with broadly rounded outer corners and an obtuse-angled snout. It has a whip-like tail with both an upper keel and a lower fin fold, and a line of small tubercles along the middle of its back.

Striped stingaree species of fish

The striped stingaree is a common but little-known species of stingray in the family Urolophidae, endemic to shallow, inshore waters off southwestern Australia. Reaching 61 cm (24 in) long, this species is characterized by an oval, grayish to brownish disc with darker mask-like markings around the eyes and paired blotches at the center of the disc that are extended posteriorly into horizontal lines. Its nostrils have enlarged lobes on the outer margins and a skirt-shaped curtain of skin with a deeply fringed trailing margin in between. Its tail terminates in a relatively large leaf-shaped caudal fin, and bears a small dorsal fin just before the stinging spine. The rounded, flexible disc of the striped stingaree enable it to maneuver through the rocks, reefs, and seagrass that comprise its favored habitats. The International Union for Conservation of Nature (IUCN) has listed this species under Least Concern; it is seldom caught by fisheries due to its habitat preferences.

The masked stingaree is a common species of stingray in the family Urolophidae, endemic to southwestern Australia. It prefers moderately deep areas of sand or seagrass some distance from shore, though it can be found in very shallow water or to a depth of 115 m (377 ft). The masked stingaree can be identified by the two large, dark blotches on the upper surface of its rounded pectoral fin disc, one of which encompasses its eyes like a mask. The outer rims of its nostrils are expanded into prominent lobes, while between the nostrils is a skirt-like curtain of skin with a deeply fringed trailing margin. Its tail bears a small dorsal fin just before the stinging spine, and end in a leaf-like caudal fin. This species grows up to 31 cm (12 in) across.

The yellow shovelnose stingaree is a little-known species of stingray in the family Urolophidae, endemic to the outer continental shelf off Western Australia at a depth of 100–210 m (330–690 ft). Growing to 39 cm (15 in) long, this species has an oval pectoral fin disc with a rather elongated, triangular snout, and a short tail with a caudal fin but no dorsal fin. There are prominent lobes outside of its nostrils, and a skirt-shaped flap of skin with a deeply fringed trailing margin in between. Above, this ray is an almost completely uniform light to dark yellow color, which darkens on the caudal fin. The International Union for Conservation of Nature (IUCN) assesses the yellow shovelnose stingaree as least concern, as there is minimal fishing within its range.

The patchwork stingaree is a little-known species of stingray in the family Urolophidae, with a disjunct distribution off northwestern and northeastern Australia. It usually inhabits the outer continental shelf, at a depth of 60–320 m (200–1,050 ft). This species has a diamond-shaped pectoral fin disc much wider than long, and a short, flattened tail with a prominent dorsal fin and leaf-like caudal fin. There is a skirt-shaped curtain of skin between its nostrils. Its dorsal color pattern resembles a mosaic of dark brown rings with light-colored centers, separated by fine reticulated lines. The International Union for Conservation of Nature (IUCN) has listed the patchwork stingaree under Least Concern, as it is subject to minimal fishing pressure.

Spotted stingaree species of fish

The spotted stingaree is an uncommon species of stingray in the family Urolophidae, endemic to shallow waters along the coast of southern Australia. It favors rocky reefs and seagrass beds. This species can be readily identified by its nearly circular, dark-colored pectoral fin disc, adorned with a complex pattern of white or cream spots. Its eastern and western forms differ slightly in coloration and have been regarded as separate species. There is a skirt-shaped curtain of skin between its nostrils. Its tail is fairly thick and terminates in a short leaf-shaped caudal fin; a relatively large dorsal fin is present just in front of the stinging spine.

The Coral Sea stingaree is a little-known species of stingray in the family Urolophidae, found at a depth of 171–310 m (561–1,017 ft) around the edge of the continental shelf off northern Queensland. Growing to a length of 48 cm (19 in), this species has a diamond-shaped pectoral fin disc with a protruding snout and a skirt-shaped flap of skin between the nostrils. Its tail bears a low dorsal fin before the stinging spine and terminates in a short leaf-shaped caudal fin. Its upper surface is grayish or brownish, sometimes with tiny dark spots. The Coral Sea stingaree may represent two closely similar species, one large and one small. There is very little fishing activity within its range, and thus it has been listed under Least Concern by the International Union for Conservation of Nature (IUCN).

The greenback stingaree is a little-known species of stingray in the family Urolophidae, endemic to the outer continental shelf and upper continental slope off southeastern Australia. Growing to a length of 51 cm (20 in), this species has a diamond-shaped pectoral fin disc wider than long and uniformly light green in color above. Between its nostrils is a skirt-shaped curtain of skin. Its tail bears skin folds on either side and a deep, lanceolate caudal fin, but lacks a dorsal fin.

Broad stingray species of fish

The broad stingray, also known as the brown stingray or Hawaiian stingray, is a species of stingray in the family Dasyatidae. The predominant species of stingray in the inshore waters of the Hawaiian Islands, this benthic fish typically inhabits sandy or muddy flats at depths greater than 15 m (49 ft). Usually growing to 1 m (3 ft) across, the broad stingray has a wide, diamond-shaped pectoral fin disc with a protruding snout tip and a long tail with a ventral fin fold. At night, this species actively forages for bottom-dwelling invertebrates and bony fishes, often near the boundaries of reefs. Reproduction is aplacental viviparous. As substantial threats to its population do not seem to exist, the International Union for Conservation of Nature has listed this species as least concern.

Smalleye stingray species of fish

The smalleye stingray is a large species of stingray in the family Dasyatidae, measuring up to 2.2 m (7.2 ft) across. Rare but widely distributed, it is found in the Indo-Pacific from Mozambique to India to northern Australia. This species may be semi-pelagic in nature, inhabiting both deeper waters and shallow coastal reefs and estuaries. It is characterized by a diamond-shaped pectoral fin disc much wider than long, a tail that is broad and flattened in front of the spine but whip-like behind, and large white spots over its back.

Jenkins whipray species of stingray (Himantura jenkinsii)

The Jenkins' whipray is a species of stingray in the family Dasyatidae, with a wide distribution in the Indo-Pacific region from South Africa to the Malay Archipelago to northern Australia. This large species grows to 1.5 m (4.9 ft) across and has a broad, diamond-shaped pectoral fin disc and a whip-like tail without fin folds. It has a band of heart-shaped dermal denticles running from between the eyes to the tail on its upper surface, along with a characteristic row of large spear-like thorns along the midline. It is uniform yellowish brown above, becoming grayish on the tail past the stinging spine, and white below; there is apparently a spotted color variant that had previously been described as a different species, the dragon stingray.

Black-spotted whipray species of fish

The black-spotted whipray is a species of stingray in the family Dasyatidae, found in coastal waters off southern New Guinea and northern Australia. Long thought to be a variant of the related brown whipray, 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).

Dwarf black stingray species of fish

The dwarf black stingray is a little-known species of stingray in the family Dasyatidae, found off northwestern Australia and perhaps throughout Southeast Asia at depths of 60–185 m (197–607 ft). Growing to a width of 51 cm (20 in), this species is characterized by an angular, diamond-shaped pectoral fin disc with a short row of spear-like thorns along the midline of the back and few dermal denticles elsewhere. Its tail bears a long fin fold along the bottom and a much shorter ridge along the top, both past the stinging spine. Plain brownish in color above, this ray can range from light to very dark. In some parts of its range, this species is occasionally caught incidentally by fisheries and sold for meat.

References

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  12. Moravec, F. & J.L. Justine (2006). "Three nematode species from elasmobranchs off New Caledonia". Systematic Parasitology. 64 (2): 131–145. doi:10.1007/s11230-006-9034-x. PMID   16773474.
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