The thorntail stingray, black stingray, or longtail stingray (''Dasyatis thetidis'') is a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of
stingray in the
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Dasyatidae. It is found off
southern Africa
Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number o ...
,
Australia, and
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
from the
intertidal zone to a depth of . This
bottom-dweller inhabits soft-bottomed
habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
s such as
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') ...
s,
estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...
, and
reef
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...
s. Growing to across and over 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
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...
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 invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s and
bony fishes. It has been known to gather in large groups during summertime. Like other stingrays, it is
aplacental viviparous
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop ins ...
, with the developing
embryos sustained to term by
histotroph
Uterine glands or endometrial glands are tubular glands, lined by ciliated columnar epithelium, found in the functional layer of the endometrium that lines the uterus. Their appearance varies during the menstrual cycle. During the proliferative ph ...
("uterine milk") produced by the mother. The
venom
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a st ...
ous stinging spine of the thorntail stingray can inflict a painful injury, though it is not aggressive towards humans. It is caught by
commercial
Commercial may refer to:
* a dose of advertising conveyed through media (such as - for example - radio or television)
** Radio advertisement
** Television advertisement
* (adjective for:) commerce, a system of voluntary exchange of products and s ...
and
recreational fishers, though the impact of such activities on its population is unknown. As a result, the
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of nat ...
(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
Australian
ichthyologist James Douglas Ogilby originally described the thorntail stingray from four specimens collected off
New South Wales
)
, nickname =
, image_map = New South Wales in Australia.svg
, map_caption = Location of New South Wales in AustraliaCoordinates:
, subdivision_type = Country
, subdivision_name = Australia
, established_title = Before federation
, es ...
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''.
Other
common names for this species include black skate, black stingaree, long-tailed stingaree, longtail black stingray, thorn stingray, and thorntail ray.
Distribution and habitat
The thorntail stingray is found off
southern Africa
Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number o ...
from
Algoa Bay,
South Africa
South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
to Barra da Falsa,
Mozambique
Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...
and
Réunion, as well as off Australia from
Shark Bay to northern
New South Wales
)
, nickname =
, image_map = New South Wales in Australia.svg
, map_caption = Location of New South Wales in AustraliaCoordinates:
, subdivision_type = Country
, subdivision_name = Australia
, established_title = Before federation
, es ...
,
Lord Howe Island
Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland P ...
,
Norfolk Island, and New Zealand.
It is fairly common off Australia and New Zealand and less so elsewhere.
Favoring inshore habitats with soft bottoms, this
benthic species is commonly encountered in
estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...
and
lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') ...
s, around rocky and
coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
C ...
s, and over reef flats. In Australia, it has been known to swim up
river
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...
s. 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 .
Description
![Thorntail stingray new zealand](https://upload.wikimedia.org/wikipedia/commons/e/e6/Thorntail_stingray_new_zealand.jpg)
One of the largest members of its family, the thorntail stingray reaches at least long, across, and in weight. This species has a diamond-shaped
pectoral fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...
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
papilla
Papilla (Latin, 'nipple') or papillae may refer to:
In animals
* Papilla (fish anatomy), in the mouth of fish
* Basilar papilla, a sensory organ of lizards, amphibians and fish
* Dental papilla, in a developing tooth
* Dermal papillae, part of ...
e 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
A quincunx () is a geometric pattern consisting of five points arranged in a cross, with four of them forming a square or rectangle and a fifth at its center. The same pattern has other names, including "in saltire" or "in cross" in heraldry (d ...
pattern into pavement-like surfaces.
The
pelvic fins have rounded tips and gently curved trailing margins.
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. 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.
The longer tail, presence of thorns, and absence of white dots atop the disc differentiate this species from the
short-tail stingray
The short-tail stingray or smooth stingray (''Bathytoshia brevicaudata'') is a common species of stingray in the family Dasyatidae. It occurs off southern Africa, typically offshore at a depth of , and off southern Australia and New Zealand, f ...
(''D. brevicaudata''), another giant stingray that shares its range.
Biology and ecology
![Dasyatis thetidis 2](https://upload.wikimedia.org/wikipedia/commons/0/05/Dasyatis_thetidis_2.jpg)
During the day, thorntail stingrays are often seen resting on patches of sand.
[Anthoni, J.F. (2007)]
The mystery of the social sting rays
Seafriends. Retrieved on January 7, 2010. This species preys mainly upon
crabs,
mantis shrimp,
bivalves,
polychaete worm
Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made ...
s, and
conger eels.
Off New Zealand, both it and the short-tail stingray regularly fall prey to local
killer whale
The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only extant species in the genus ''Orcinus'' and is recognizable by its black-and-white ...
s (''Orcinus orca''). A known
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
of this species is the
nematode ''Echinocephalus overstreeti''. Thorntail stingrays have been reported to congregate in warm, shallow waters during the summer, possibly for reproductive purposes.
This species is
aplacental viviparous
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop ins ...
like other stingrays.
Human interactions
The tail spine of the thorntail stingray is potentially injurious to humans.
It is reportedly unaggressive and approachable, and can be conditioned to accept being "ridden" by divers.
At
Hamelin Bay
Hamelin Bay is a bay and a locality on the southwest coast of Western Australia between Cape Leeuwin and Cape Naturaliste. It is named after French explorer Jacques Félix Emmanuel Hamelin, who sailed through the area in about 1801. It is sou ...
,
Western Australia
Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...
, 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.
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
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of nat ...
(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.
In June 2018 the New Zealand
Department of Conservation
An environmental ministry is a national or subnational government agency politically responsible for the environment and/or natural resources. Various other names are commonly used to identify such agencies, such as Ministry of the Environment ...
classified the thorntail stingray as "Not Threatened" with the qualifier "Secure Overseas" under the
New Zealand Threat Classification System.
References
{{Taxonbar, from=Q141884
Dasyatis
Taxobox binomials not recognized by IUCN