Cowtail stingray
Encyclopedia
The cowtail stingray, Pastinachus sephen, is a species of stingray
in the family Dasyatidae, widespread in the Indo-Pacific
region and occasionally entering freshwater
habitat
s. Other common name
s include banana-tail ray, drab stingray, fantail ray, feathertail stingray, and frill tailed sting ray. This species is sometimes placed in the genus Dasyatis
or Hypolophus (an obsolete synonym of Pastinachus). The most distinctive characteristic of the cowtail stingray is the large, flag
-like ventral fold on its tail
, which is especially prominent when the ray is swimming. This species is targeted by commercial fisheries
as a source of high-quality shagreen
, a type of leather
, and its populations are now under threat from heavy exploitation.
and the Red Sea
to Japan
and Australia
, including Melanesia
and Micronesia
. They are amphidromous and known to enter estuaries and river
s. This species is the most commonly reported stingray from fresh water in Southeast Asia, and there is a record from the Ganges River
some 2,200 km (1,370 mi) from the sea. They are usually found on sandy bottoms in coastal waters and on coral reef
s to a depth of 60 meters (200 ft).
The pectoral fin disk of the cowtail stingray is very thick, with almost straight anterior margins and rounded apices, and measuring 1.1-1.3 times as long as wide. The snout
is broadly rounded and blunt. The eye
s are very small and widely spaced. The mouth
is narrow, with 20 rows of distinctive hexagonal, high-crowned teeth in each jaw
and five papilla
e on the mouth floor. The tail
is broad-based, with a filamentous tip and a single venom
ous spine
located well backwards of the pelvic fins. There is no upper tail fold; the high ventral tail fold measures 2-3 times the height of the tail but does not reach the tip.
The disk surface is covered by a broad band of fine dermal denticles extending from near the tip of the snout to the upper surface of the tail, excluding the extreme margins of the disk. Newborns are entirely smooth but develop denticles quickly after birth. Juveniles have four circular tubercles at the center of the disk, which often become indistinct in adults. The coloration is a uniform grayish brown to black above and mostly white below. The tail fold and tip are black. This species may reach 3 meters (10 ft) long and 1.8 meters (6 ft) across, and 250 kg (550 lbs) in weight.
Cowtail stingrays are solitary foragers that feed on bony fishes (including leiognathids, Nemipterus, and soles
), crustacean
s, polychaete worms, sipunculids, and molluscs. The cowtail stingray is in turn preyed upon by various species of hammerhead
and requiem shark
s, as well as by the bottlenose dolphin
(Tursiops aduncus). When threatened, they consistently flee at a 45° angle away from the predator, a trajectory that allows them to maximize the distance covered while still keeping the predator within their field of vision.
Like other stingrays, reproduction in this species is ovoviviparous, with the embryo
s sustained in late development by histotroph ("uterine milk") delivered via specialized structures. The females giving birth to live young measuring 18 cm (7 in) across or more. Single young individuals have been reported year-round in the Strait of Malacca
; juveniles have more pointed snouts than adults. Adults are sometimes accompanied by remora
s or trevallies. Known parasites of the cowtail stingray include Dendromonocotyle ardea, Decacotyle tetrakordyle, and Pterobdella amara.
Observations of cowtail stingrays in Shark Bay
, Australia
, show that this species enters shallow, sandy flats during high tide
to rest for a minimum of four hours. They often form small groups when resting, particularly when visibility is poor such as in turbid
water or under low light conditions. The typical size of such groups is three individuals (larger groups, up to nine, are rare), arranged in a "rosette" formation with their tails pointing outward. This appears to be an anti-predator behavior, as the close circular arrangement of the rays allows them to see predators approaching from any direction. The rosette also orients their less critical tails, containing mechanoreceptor
s that comprise a secondary warning system, towards potential threats. The members of the group will flee in concert, reducing a predator's ability to target any one individual. Cowtail stingrays also preferentially form mixed-species groups with reticulate whiprays (Himantura uarnak), likely because the whiprays are better able to detect predators due to their longer tails.
The serrated spine of the cowtail stingray is potentially dangerous, and this species is regarded as particularly dangerous to handle as its long tail is capable of reaching over its back to strike someone gripping it from the front. Small to moderate numbers of cowtail stingrays are caught as bycatch
in trawls and marketed for meat
throughout their range, and their tough skin is used to polish wood
. This species is also the primary source of shagreen
or galuchat, a type of leather
, for which it has been valued since ancient times due to the large size and regular arrangement of its dorsal tubercles (called "pearls" in the trade from their nacreous appearance after being rubbed down, hence the old name "pearled ray").
A boom in the international shagreen trade since the 1990s
, with the material being used in many fashion accessories from wallet
s to fancy pen
s, has led to enormous numbers of cowtail stingrays being harvested in Southeast Asia. As stingrays are slow-reproducing, long-lived animals, there are fears that this unregulated exploitation is unsustainable and will lead to a population collapse.
Stingray
The stingrays are a group of rays, which are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae , Plesiobatidae , Urolophidae , Urotrygonidae , Dasyatidae , Potamotrygonidae The...
in the family Dasyatidae, widespread in the Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
region and occasionally entering freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s. Other common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s include banana-tail ray, drab stingray, fantail ray, feathertail stingray, and frill tailed sting ray. This species is sometimes placed in the genus Dasyatis
Dasyatis
Dasyatis is a genus of stingray. The members of the genus Neotrygon were formerly included in Dasyatis.-Species:...
or Hypolophus (an obsolete synonym of Pastinachus). The most distinctive characteristic of the cowtail stingray is the large, flag
Flag
A flag is a piece of fabric with a distinctive design that is usually rectangular and used as a symbol, as a signaling device, or decoration. The term flag is also used to refer to the graphic design employed by a flag, or to its depiction in another medium.The first flags were used to assist...
-like ventral fold on its tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
, which is especially prominent when the ray is swimming. This species is targeted by commercial fisheries
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
as a source of high-quality shagreen
Shagreen
Shagreen is a type of leather or rawhide consisting of rough untanned skin, formerly made from a horse's back or that of an onager . Shagreen is now commonly made of the skins of sharks and rays....
, a type of leather
Leather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...
, and its populations are now under threat from heavy exploitation.
Distribution and habitat
The cowtail stingray has a widespread distribution in the tropical waters of the Indo-Pacific, from South AfricaSouth Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
and the Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
to Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, including Melanesia
Melanesia
Melanesia is a subregion of Oceania extending from the western end of the Pacific Ocean to the Arafura Sea, and eastward to Fiji. The region comprises most of the islands immediately north and northeast of Australia...
and Micronesia
Micronesia
Micronesia is a subregion of Oceania, comprising thousands of small islands in the western Pacific Ocean. It is distinct from Melanesia to the south, and Polynesia to the east. The Philippines lie to the west, and Indonesia to the southwest....
. They are amphidromous and known to enter estuaries and river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s. This species is the most commonly reported stingray from fresh water in Southeast Asia, and there is a record from the Ganges River
Ganges River
The Ganges or Ganga, , is a trans-boundary river of India and Bangladesh. The river rises in the western Himalayas in the Indian state of Uttarakhand, and flows south and east through the Gangetic Plain of North India into Bangladesh, where it empties into the Bay of Bengal. By discharge it...
some 2,200 km (1,370 mi) from the sea. They are usually found on sandy bottoms in coastal waters and on coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s to a depth of 60 meters (200 ft).
Description
Snout
The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...
is broadly rounded and blunt. The eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s are very small and widely spaced. The mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
is narrow, with 20 rows of distinctive hexagonal, high-crowned teeth in each jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...
and five papilla
Papilla (fish mouth structure)
The papilla, in certain kinds of fish, particularly rays, sharks, and catfish, are small lumps of dermal tissue found in the mouth, where they are "distributed uniformly on the tongue, palate, and pharynx"...
e on the mouth floor. The tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
is broad-based, with a filamentous tip and a single venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous spine
Spine (zoology)
A spine is a hard, thorny or needle-like structure which occurs on various animals. Animals such as porcupines and sea urchins grow spines as a self-defense mechanism. Spines are often formed of keratin...
located well backwards of the pelvic fins. There is no upper tail fold; the high ventral tail fold measures 2-3 times the height of the tail but does not reach the tip.
The disk surface is covered by a broad band of fine dermal denticles extending from near the tip of the snout to the upper surface of the tail, excluding the extreme margins of the disk. Newborns are entirely smooth but develop denticles quickly after birth. Juveniles have four circular tubercles at the center of the disk, which often become indistinct in adults. The coloration is a uniform grayish brown to black above and mostly white below. The tail fold and tip are black. This species may reach 3 meters (10 ft) long and 1.8 meters (6 ft) across, and 250 kg (550 lbs) in weight.
Biology and ecology
Sole (fish)
Sole is a group of flatfish belonging to several families. Generally speaking, they are members of the family Soleidae, but, outside Europe, the name sole is also applied to various other similar flatfish, especially other members of the sole suborder Soleoidei as well as members of the flounder...
), crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, polychaete worms, sipunculids, and molluscs. The cowtail stingray is in turn preyed upon by various species of hammerhead
Hammerhead shark
The hammerhead sharks are a group of sharks in the family Sphyrnidae, so named for the unusual and distinctive structure of their heads, which are flattened and laterally extended into a "hammer" shape called a "cephalofoil". Most hammerhead species are placed in the genus Sphyrna while the...
and requiem shark
Requiem shark
Requiem sharks are a family, Carcharhinidae, of sharks in the order Carcharhiniformes, containing migratory, live-bearing sharks of warm seas such as the tiger shark, the blue shark, the bull shark, and the milk shark.The name may be related to the French word for shark, "requin", itself of...
s, as well as by the bottlenose dolphin
Bottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
(Tursiops aduncus). When threatened, they consistently flee at a 45° angle away from the predator, a trajectory that allows them to maximize the distance covered while still keeping the predator within their field of vision.
Like other stingrays, reproduction in this species is ovoviviparous, with the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s sustained in late development by histotroph ("uterine milk") delivered via specialized structures. The females giving birth to live young measuring 18 cm (7 in) across or more. Single young individuals have been reported year-round in the Strait of Malacca
Strait of Malacca
The Strait of Malacca is a narrow, stretch of water between the Malay Peninsula and the Indonesian island of Sumatra. It is named after the Malacca Sultanate that ruled over the archipelago between 1414 to 1511.-Extent:...
; juveniles have more pointed snouts than adults. Adults are sometimes accompanied by remora
Remora
The remora , sometimes called a suckerfish or sharksucker, is an elongated, brown fish in the order Perciformes and family Echeneidae...
s or trevallies. Known parasites of the cowtail stingray include Dendromonocotyle ardea, Decacotyle tetrakordyle, and Pterobdella amara.
Observations of cowtail stingrays in Shark Bay
Shark Bay
Shark Bay is a World Heritage listed bay in Western Australia. The term may also refer to:* the locality of Shark Bay, now known as Denham* Shark Bay Marine Park* Shark Bay , a shark exhibit at Sea World, Gold Coast, Australia* Shire of Shark Bay...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, show that this species enters shallow, sandy flats during high tide
High Tide
High Tide was a band formed in 1969 by Tony Hill , Simon House , Peter Pavli and Roger Hadden .-History:...
to rest for a minimum of four hours. They often form small groups when resting, particularly when visibility is poor such as in turbid
Turbidity
Turbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....
water or under low light conditions. The typical size of such groups is three individuals (larger groups, up to nine, are rare), arranged in a "rosette" formation with their tails pointing outward. This appears to be an anti-predator behavior, as the close circular arrangement of the rays allows them to see predators approaching from any direction. The rosette also orients their less critical tails, containing mechanoreceptor
Mechanoreceptor
A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. There are four main types in the glabrous skin of humans: Pacinian corpuscles, Meissner's corpuscles, Merkel's discs, and Ruffini corpuscles...
s that comprise a secondary warning system, towards potential threats. The members of the group will flee in concert, reducing a predator's ability to target any one individual. Cowtail stingrays also preferentially form mixed-species groups with reticulate whiprays (Himantura uarnak), likely because the whiprays are better able to detect predators due to their longer tails.
Relationship to humans
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
in trawls and marketed for meat
Meat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...
throughout their range, and their tough skin is used to polish wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
. This species is also the primary source of shagreen
Shagreen
Shagreen is a type of leather or rawhide consisting of rough untanned skin, formerly made from a horse's back or that of an onager . Shagreen is now commonly made of the skins of sharks and rays....
or galuchat, a type of leather
Leather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...
, for which it has been valued since ancient times due to the large size and regular arrangement of its dorsal tubercles (called "pearls" in the trade from their nacreous appearance after being rubbed down, hence the old name "pearled ray").
A boom in the international shagreen trade since the 1990s
1990s
File:1990s decade montage.png|From left, clockwise: The Hubble Space Telescope floats in space after it was taken up in 1990; American F-16s and F-15s fly over burning oil fields and the USA Lexie in Operation Desert Storm, also known as the 1991 Gulf War; The signing of the Oslo Accords on...
, with the material being used in many fashion accessories from wallet
Wallet
A wallet, or billfold, is a small, flat case that is used to carry personal items such as cash, credit cards, identification documents , photographs, business cards and other paper or laminated cards...
s to fancy pen
Pen
A pen is a device used to apply ink to a surface, usually paper, for writing or drawing. Historically, reed pens, quill pens, and dip pens were used, with a nib of some sort to be dipped in the ink. Ruling pens allow precise adjustment of line width, and still find a few specialized uses, but...
s, has led to enormous numbers of cowtail stingrays being harvested in Southeast Asia. As stingrays are slow-reproducing, long-lived animals, there are fears that this unregulated exploitation is unsustainable and will lead to a population collapse.