Honeycomb stingray
Encyclopedia
The reticulate whipray or honeycomb stingray (Himantura uarnak) is a species
of stingray
in the family Dasyatidae. It inhabits coastal and brackish water
s across the Indo-Pacific
region from South Africa
to Taiwan
to Australia
, favoring sandy habitat
s. A large species reaching 2 m (6.6 ft) in width, the reticulate whipray has a diamond-shaped pectoral fin disc and an extremely long tail without fin folds. Both its common
and scientific names refer to its ornate dorsal color pattern of many small, close-set dark spots or reticulations on a lighter background. However, the reticulate whipray is only one of several large spotted stingrays in the Indo-Pacific which, coupled with the variability of its coloration with age and locality, has resulted in a great deal of taxonomic
confusion.
Often encountered resting on the bottom during daytime, the reticulate whipray is a predator of bottom-dwelling invertebrate
s and bony fishes. Like other stingrays, it is aplacental viviparous, with the developing embryo
s nourished at first by yolk and later by histotroph ("uterine milk"). Females bear litters of up to five pups in summer, following a gestation period
of a year. The reticulate whipray is fished in Southeast Asia
and parts of the Indian Ocean
for meat, skin, cartilage
, and other purposes. It is highly susceptible to population depletion because of its large size, inshore habits, and low reproductive rate, and is additionally threatened by extensive habitat degradation. Consequently, the International Union for Conservation of Nature (IUCN) has assessed this species as Vulnerable
.
published Descriptiones animalium – avium, amphibiorum, piscium, insectorum, vermium: quæ in itinere orientali observavit, the work of his late friend, the Swedish naturalist
Peter Forsskål
. Within Forsskål had described Raja sephen, now commonly known as the cowtail stingray
, with a spotted variant he called uarnak, derived from an Arabic word that describes the color pattern. No type specimen was designated. Forsskål's account formed the basis for two subsequent writings that named the spotted ray as a distinct species: Pierre Joseph Bonnaterre
's Raia scherit in 1788, and Johann Friedrich Gmelin
's Raja uarnak in 1789. Although Bonnaterre's name was published first and thus would have had precedence, later authorities have regarded Forsskål's uarnak as the earliest available name even though it was not initially part of a binomial
. Consequently, modern sources give uarnak as the valid specific epithet and either Gmelin or Forsskål as the species authority. In 1837, Johannes Peter Müller
and Friedrich Gustav Jakob Henle
included the reticulate whipray in the newly created genus Himantura; David Starr Jordan
and Barton Warren Evermann
made it the type species
in 1896.
The reticulate whipray is closely related to H. undulata and H. leoparda, which share much of its range. All three species are very similar in size, shape, and color pattern, resulting in a long history of taxonomic confusion that only recently is starting to be untangled. In 2004, Mabel Manjaji described the 'uarnak' species complex
, containing H. fai, H. gerrardi, H. jenkinsii, H. leoparda, H. toshi, H. uarnak, and H. undulata, plus three more undescribed species. The reticulate whipray itself varies in appearance throughout its range, and further taxonomic comparisons are required to determine whether its spotted and reticulated color morphs in fact represent different species. Alternate common name
s for this ray include coachwhip ray, leopard stingray, longtail stingray, and marbled stingray; some of these names are shared by other, similar species.
, with a range extending from off eastern South Africa
to the Arabian Peninsula
, westward along the coast of the Indian subcontinent
to Southeast Asia
, and reaching as far as Taiwan
and the Ryukyu Islands
to the north, and New Guinea
and northern Australia
to the southeast. It has also colonized the eastern Mediterranean Sea
through the Suez Canal
. This species seems to be common only in Australian waters, where it occurs from Shark Bay
to Brisbane
.
Bottom-dwelling in nature, the reticulate whipray is generally encountered over sandy flats near beach
es, in lagoon
s, and around coral reef
s, from the intertidal zone
to offshore waters 50 m (164 ft) deep or more. In Shark Bay
, it frequents intertidal sand flats during the warm season, and shifts to slightly deeper seagrass
patches in the cold season. This species is tolerant of low salinities
and has been known to enter estuaries and mangrove swamps, though records from fresh water
in Southeast Asia are unverified and may represent misidentifications. Its preferred water temperatures are 23–26 °C (73.4–78.8 F).
The pectoral fin disc of the reticulate whipray is diamond-shaped and wider than long, with the leading margins almost straight and the snout and outer corners angular. In juveniles, the disc is about as wide as long, with a more obtuse snout and rounded corners. The eyes are small and immediately followed by the spiracle
s (paired respiratory
openings). A short and wide curtain of skin with a minutely fringed rear margin is present between the long, thin nostril
s. The mouth is relatively small, with a deep concavity at the center of the lower jaw and shallow furrows at the corners extending onto the lower jaw. A row of 4–5 papillae (nipple-like structures) is found across the floor of the mouth. There are 26–40 upper tooth rows and 27–44 lower tooth rows. The pelvic fins are small and triangular. The tail is whip-like and extremely thin, measuring 3–3.5 times as long as the disc when intact, and lacks fin folds. Usually one serrated stinging spine is located on the upper surface on the tail, some distance from the base.
Adult rays have a wide band of flattened, heart-shaped dermal denticles that extend from between the eyes to the tail spine, increasing in density with age, along with two large pearl thorns at the center of the back. The tail behind the spine is covered by small thorns. The dorsal band of denticles is largely developed by the time the juveniles are 50 cm (19.7 in) across. The coloration of the reticulate whipray varies substantially with age and locality. Adults generally have a dorsal pattern of numerous closely spaced dark brown spots or reticulations on a beige to yellow-brown background, which becomes blackish past the spine with lighter bands on the sides. The underside is pale, without markings. Juveniles are yellowish above with tiny, densely packed dark spots, around seven spots in a line between the spiracles, and three rows of spots in front of the sting. This large species has been reported to reach a disc width of 2 m (6.6 ft), a total length of 6 m (19.7 ft), and a weight of 120 kg (264.6 lb).
, Western Australia
, this ray can be found resting singly or in small groups in very shallow water during high tide
. Its lateral line
extends to the tip of its extremely long tail, giving it advance warning of approaching predators such as bottlenose dolphin
s (Tursiops aduncus) and hammerhead shark
s (Sphyrna). The cowtail stingray
(Pastinachus sephen) prefers to rest with the reticulate whipray over others of its own species, because the whiprays' longer tails grant them superior predator detection. These mixed-species groups often settle into a "rosette" with their tails pointing radially outward for maximum predator awareness.
The reticulate whipray preys on a variety of benthic and neritic organism
s, including crab
s, shrimp
s, mantis shrimp
s, bivalves, gastropods, worm
s, jellyfish
, and bony fishes. In the western Indian Ocean, about two-thirds of its diet consists of fishes, in particular ponyfish
and anchovies, with shrimps and other crustacean
s making up most of the remainder. By contrast, rays in Australian waters are apparently not piscivorous, and are known to consume penaeid prawn
s. Known parasites of this species include Anthrobothrium loculatum, Dendromonocotyle colorni, Halysiorhynchus macrocephalus, Monocotyle helicophallus, M. multiparous, and M. spiremae, Thaumatocotyle australensis, and Tylocephalum chiralensis.
Like other stingrays, the reticulate whipray is aplacental viviparous: the developing embryo
s are initially sustained by yolk, which is later supplanted by histotroph ("uterine milk", enriched with protein
s and lipid
s) produced by the mother. Females give birth to up to five pups in the summer, after a year-long gestation period
. Off South Africa, the newborns measure 28–30 cm (11–11.8 in) across and sexual maturation is attained at a disc width of approximately 1 m (3.3 ft), which corresponds to an age of 4-5. Off Australia, the newborns measure 21–28 cm (8.3–11 in) across, with males reported to mature at 82–84 cm (32.3–33.1 in) across. The juveniles of this species, H. leoparda, and H. undulata differ in birth size, disc shape, denticle development, and amount of spotting, and are in fact more distinct from each other than are adults of the three species. Shark Bay may serve as a nursery area for young rays.
, who usually release it alive. This species is caught by intensive artisanal
and commercial fisheries operating in Southeast Asia and parts of the Indian Ocean, using bottom trawls, gillnet
s and tangle net
s, beach seines, and longlines. In particular, it is caught in substantial numbers by an Indonesia
n trawl fishery targeting wedgefishes in the Arafura Sea
. The meat, skin, and cartilage
are utilized, though this species is not a highly valued food fish. It also has applications in Chinese medicine, and its tail may be sold as a curio.
The International Union for Conservation of Nature (IUCN) has listed the reticulate whipray as Vulnerable
. Its large size, inshore habitat preferences, and slow reproductive rate render it susceptible to overfishing
. Although specific data is lacking, significant declines in overall ray catches have been documented within its range, including in the Gulf of Thailand
, the Arafura Sea, and off Pakistan
. Habitat degradation also threatens this species: over 30% of the mangroves in Indonesia and Malaysia have been cleared since 1980, while pollution
and destructive fishing practices may have also taken their toll. Australian waters offer the reticulate whipray a refuge from fishing pressure, as there it is not targeted commercially and the installation of Turtle Exclusion Devices (TEDs) have reduced bycatch
mortality. However, there are indications of increasing illegal fishing in Australian territory by Indonesian vessels.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of stingray
Myliobatiformes
Myliobatiformes is one of the four orders of batoids, cartilaginous fishes related to sharks. They were formerly included in the order Rajiformes, but more recent phylogenetic studies have shown that the myliobatiforms are a monophyletic group, and that its more derived members evolved their...
in the family Dasyatidae. It inhabits coastal and brackish water
Brackish water
Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root "brak," meaning "salty"...
s across 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 from South Africa
South 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...
to Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
to 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...
, favoring sandy 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. A large species reaching 2 m (6.6 ft) in width, the reticulate whipray has a diamond-shaped pectoral fin disc and an extremely long tail without fin folds. Both its common
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...
and scientific names refer to its ornate dorsal color pattern of many small, close-set dark spots or reticulations on a lighter background. However, the reticulate whipray is only one of several large spotted stingrays in the Indo-Pacific which, coupled with the variability of its coloration with age and locality, has resulted in a great deal of taxonomic
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
confusion.
Often encountered resting on the bottom during daytime, the reticulate whipray is a predator of bottom-dwelling invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s and bony fishes. Like other stingrays, it is aplacental viviparous, with the developing 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 nourished at first by yolk and later by histotroph ("uterine milk"). Females bear litters of up to five pups in summer, following a gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
of a year. The reticulate whipray is fished in Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
and parts of the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
for meat, skin, cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
, and other purposes. It is highly susceptible to population depletion because of its large size, inshore habits, and low reproductive rate, and is additionally threatened by extensive habitat degradation. Consequently, the International Union for Conservation of Nature (IUCN) has assessed this species as Vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
.
Taxonomy and phylogeny
In 1775, Carsten NiebuhrCarsten Niebuhr
Carsten Niebuhr or Karsten Niebuhr , a German mathematician, cartographer, and explorer in the service of Denmark, is renowned for his travels on the Arabian peninsula.-Biography:...
published Descriptiones animalium – avium, amphibiorum, piscium, insectorum, vermium: quæ in itinere orientali observavit, the work of his late friend, the Swedish naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Peter Forsskål
Peter Forsskål
Peter Forsskål, sometimes spelled Pehr Forsskål, Peter Forskaol, Petrus Forskål or Pehr Forsskåhl, was a Swedish explorer, orientalist, naturalist and an apostle of Carl Linnaeus.-Early life:...
. Within Forsskål had described Raja sephen, now commonly known as the cowtail stingray
Cowtail stingray
The cowtail stingray, Pastinachus sephen, is a species of stingray in the family Dasyatidae, widespread in the Indo-Pacific region and occasionally entering freshwater habitats. Other common names include banana-tail ray, drab stingray, fantail ray, feathertail stingray, and frill tailed sting ray...
, with a spotted variant he called uarnak, derived from an Arabic word that describes the color pattern. No type specimen was designated. Forsskål's account formed the basis for two subsequent writings that named the spotted ray as a distinct species: Pierre Joseph Bonnaterre
Pierre Joseph Bonnaterre
Abbé Pierre Joseph Bonnaterre was a French naturalist who contributed sections on cetaceans, mammals, birds, reptiles, amphibians, and insects to the Tableau encyclopédique et méthodique...
's Raia scherit in 1788, and Johann Friedrich Gmelin
Johann Friedrich Gmelin
Johann Friedrich Gmelin was a German naturalist, botanist, entomologist, herpetologist and malacologist.- Education :Johann Friedrich Gmelin was born as the eldest son of Philipp Friedrich Gmelin in 1748 in Tübingen...
's Raja uarnak in 1789. Although Bonnaterre's name was published first and thus would have had precedence, later authorities have regarded Forsskål's uarnak as the earliest available name even though it was not initially part of a binomial
Binomial nomenclature
Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...
. Consequently, modern sources give uarnak as the valid specific epithet and either Gmelin or Forsskål as the species authority. In 1837, Johannes Peter Müller
Johannes Peter Müller
Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...
and Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle was a German physician, pathologist and anatomist. He is credited with the discovery of the loop of Henle in the kidney. His essay "On Miasma and Contagia" was an early argument for the germ theory of disease...
included the reticulate whipray in the newly created genus Himantura; David Starr Jordan
David Starr Jordan
David Starr Jordan, Ph.D., LL.D. was a leading eugenicist, ichthyologist, educator and peace activist. He was president of Indiana University and Stanford University.-Early life and education:...
and Barton Warren Evermann
Barton Warren Evermann
Barton Warren Evermann was an American ichthyologist. He was born in Monroe County, Iowa, and graduated from Indiana University in 1886. For 10 years, he served as teacher and superintendent of schools in Indiana and California. He was professor of biology at the Indiana State University in...
made it the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
in 1896.
The reticulate whipray is closely related to H. undulata and H. leoparda, which share much of its range. All three species are very similar in size, shape, and color pattern, resulting in a long history of taxonomic confusion that only recently is starting to be untangled. In 2004, Mabel Manjaji described the 'uarnak' species complex
Species complex
A species complex is a group of closely related species, where the exact demarcation between species is often unclear or cryptic owing to their recent and usually still incomplete reproductive isolation. Ring species, superspecies and cryptic species complex are example of species complex...
, containing H. fai, H. gerrardi, H. jenkinsii, H. leoparda, H. toshi, H. uarnak, and H. undulata, plus three more undescribed species. The reticulate whipray itself varies in appearance throughout its range, and further taxonomic comparisons are required to determine whether its spotted and reticulated color morphs in fact represent different species. Alternate 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 for this ray include coachwhip ray, leopard stingray, longtail stingray, and marbled stingray; some of these names are shared by other, similar species.
Distribution and habitat
The reticulate whipray occurs widely in the Indo-PacificIndo-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...
, with a range extending from off eastern South Africa
South 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...
to the Arabian Peninsula
Arabian Peninsula
The Arabian Peninsula is a land mass situated north-east of Africa. Also known as Arabia or the Arabian subcontinent, it is the world's largest peninsula and covers 3,237,500 km2...
, westward along the coast of the Indian subcontinent
Indian subcontinent
The Indian subcontinent, also Indian Subcontinent, Indo-Pak Subcontinent or South Asian Subcontinent is a region of the Asian continent on the Indian tectonic plate from the Hindu Kush or Hindu Koh, Himalayas and including the Kuen Lun and Karakoram ranges, forming a land mass which extends...
to Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
, and reaching as far as Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
and the Ryukyu Islands
Ryukyu Islands
The , also known as the , is a chain of islands in the western Pacific, on the eastern limit of the East China Sea and to the southwest of the island of Kyushu in Japan. From about 1829 until the mid 20th century, they were alternately called Luchu, Loochoo, or Lewchew, akin to the Mandarin...
to the north, and New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
and northern 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...
to the southeast. It has also colonized the eastern Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
through the Suez Canal
Suez Canal
The Suez Canal , also known by the nickname "The Highway to India", is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea and the Red Sea. Opened in November 1869 after 10 years of construction work, it allows water transportation between Europe and Asia without navigation...
. This species seems to be common only in Australian waters, where it occurs from 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...
to Brisbane
Brisbane
Brisbane is the capital and most populous city in the Australian state of Queensland and the third most populous city in Australia. Brisbane's metropolitan area has a population of over 2 million, and the South East Queensland urban conurbation, centred around Brisbane, encompasses a population of...
.
Bottom-dwelling in nature, the reticulate whipray is generally encountered over sandy flats near beach
Beach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...
es, in lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
s, and around 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, from the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
to offshore waters 50 m (164 ft) deep or more. 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...
, it frequents intertidal sand flats during the warm season, and shifts to slightly deeper seagrass
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
patches in the cold season. This species is tolerant of low salinities
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
and has been known to enter estuaries and mangrove swamps, though records from fresh water
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
in Southeast Asia are unverified and may represent misidentifications. Its preferred water temperatures are 23–26 °C (73.4–78.8 F).
Description
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s (paired respiratory
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
openings). A short and wide curtain of skin with a minutely fringed rear margin is present between the long, thin nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s. The mouth is relatively small, with a deep concavity at the center of the lower jaw and shallow furrows at the corners extending onto the lower jaw. A row of 4–5 papillae (nipple-like structures) is found across the floor of the mouth. There are 26–40 upper tooth rows and 27–44 lower tooth rows. The pelvic fins are small and triangular. The tail is whip-like and extremely thin, measuring 3–3.5 times as long as the disc when intact, and lacks fin folds. Usually one serrated stinging spine is located on the upper surface on the tail, some distance from the base.
Adult rays have a wide band of flattened, heart-shaped dermal denticles that extend from between the eyes to the tail spine, increasing in density with age, along with two large pearl thorns at the center of the back. The tail behind the spine is covered by small thorns. The dorsal band of denticles is largely developed by the time the juveniles are 50 cm (19.7 in) across. The coloration of the reticulate whipray varies substantially with age and locality. Adults generally have a dorsal pattern of numerous closely spaced dark brown spots or reticulations on a beige to yellow-brown background, which becomes blackish past the spine with lighter bands on the sides. The underside is pale, without markings. Juveniles are yellowish above with tiny, densely packed dark spots, around seven spots in a line between the spiracles, and three rows of spots in front of the sting. This large species has been reported to reach a disc width of 2 m (6.6 ft), a total length of 6 m (19.7 ft), and a weight of 120 kg (264.6 lb).
Biology and ecology
During the day, the reticulate whipray is generally inactive and spends much time resting motionless on the sea floor, sometimes buried in sand. In Shark BayShark 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...
, Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
, this ray can be found resting singly or in small groups in very shallow water during high tide
High Tide
High Tide was a band formed in 1969 by Tony Hill , Simon House , Peter Pavli and Roger Hadden .-History:...
. Its lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
extends to the tip of its extremely long tail, giving it advance warning of approaching predators such as bottlenose dolphin
Indo-Pacific Bottlenose Dolphin
The Indo-Pacific bottlenose dolphin is a species of bottlenose dolphin. The Indo-Pacific bottlenose dolphin grows to long, and weigh up to . It lives in the waters around India, northern Australia, South China, the Red Sea, and the eastern coast of Africa. Its back is dark grey and its belly...
s (Tursiops aduncus) and hammerhead shark
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...
s (Sphyrna). The cowtail stingray
Cowtail stingray
The cowtail stingray, Pastinachus sephen, is a species of stingray in the family Dasyatidae, widespread in the Indo-Pacific region and occasionally entering freshwater habitats. Other common names include banana-tail ray, drab stingray, fantail ray, feathertail stingray, and frill tailed sting ray...
(Pastinachus sephen) prefers to rest with the reticulate whipray over others of its own species, because the whiprays' longer tails grant them superior predator detection. These mixed-species groups often settle into a "rosette" with their tails pointing radially outward for maximum predator awareness.
The reticulate whipray preys on a variety of benthic and neritic organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s, including crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s, shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
s, mantis shrimp
Mantis shrimp
Mantis shrimp or stomatopods are marine crustaceans, the members of the order Stomatopoda. They are neither shrimp nor mantids, but receive their name purely from the physical resemblance to both the terrestrial praying mantis and the shrimp. They may reach in length, although exceptional cases of...
s, bivalves, gastropods, worm
Worm
The term worm refers to an obsolete taxon used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals, and stems from the Old English word wyrm. Currently it is used to describe many different distantly-related animals that typically have a long cylindrical...
s, jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
, and bony fishes. In the western Indian Ocean, about two-thirds of its diet consists of fishes, in particular ponyfish
Ponyfish
The ponyfishes also known as slipmouths or slimys are a small family, Leiognathidae, of fishes in the order Perciformes. They inhabit marine and brackish waters in the Indian Ocean and West Pacific....
and anchovies, with shrimps and other 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 making up most of the remainder. By contrast, rays in Australian waters are apparently not piscivorous, and are known to consume penaeid prawn
Prawn
Prawns are decapod crustaceans of the sub-order Dendrobranchiata. There are 540 extant species, in seven families, and a fossil record extending back to the Devonian...
s. Known parasites of this species include Anthrobothrium loculatum, Dendromonocotyle colorni, Halysiorhynchus macrocephalus, Monocotyle helicophallus, M. multiparous, and M. spiremae, Thaumatocotyle australensis, and Tylocephalum chiralensis.
Like other stingrays, the reticulate whipray is aplacental viviparous: the developing 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 are initially sustained by yolk, which is later supplanted by histotroph ("uterine milk", enriched with protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s and lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s) produced by the mother. Females give birth to up to five pups in the summer, after a year-long gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
. Off South Africa, the newborns measure 28–30 cm (11–11.8 in) across and sexual maturation is attained at a disc width of approximately 1 m (3.3 ft), which corresponds to an age of 4-5. Off Australia, the newborns measure 21–28 cm (8.3–11 in) across, with males reported to mature at 82–84 cm (32.3–33.1 in) across. The juveniles of this species, H. leoparda, and H. undulata differ in birth size, disc shape, denticle development, and amount of spotting, and are in fact more distinct from each other than are adults of the three species. Shark Bay may serve as a nursery area for young rays.
Human interactions
The reticulate whipray fights strongly on hook-and-line and is thus popular with recreational anglersRecreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
, who usually release it alive. This species is caught by intensive artisanal
Artisan fishing
Artisan fishing is a term used to describe small scale low-technology commercial or subsistence fishing practices. The term particularly applies to coastal or island ethnic groups using traditional techniques such as rod and tackle, arrows and harpoons, throw nets and drag nets, and traditional...
and commercial fisheries operating in Southeast Asia and parts of the Indian Ocean, using bottom trawls, gillnet
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...
s and tangle net
Tangle net
Similar to a gillnet, the tangle net, or tooth net, is a type of nylon fishing net. Left in the water for no more than two days, and allowing bycatch to be released alive, this net is considered to be less harmful that other nets. The tangle net is used in the Philippines by commercial fishermen,...
s, beach seines, and longlines. In particular, it is caught in substantial numbers by an Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
n trawl fishery targeting wedgefishes in the Arafura Sea
Arafura Sea
The Arafura Sea lies west of the Pacific Ocean overlying the continental shelf between Australia and New Guinea.-Geography:The Arafura Sea is bordered by Torres Strait and through that the Coral Sea to the east, the Gulf of Carpentaria to the south, the Timor Sea to the west and the Banda and Ceram...
. The meat, skin, and cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
are utilized, though this species is not a highly valued food fish. It also has applications in Chinese medicine, and its tail may be sold as a curio.
The International Union for Conservation of Nature (IUCN) has listed the reticulate whipray as Vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
. Its large size, inshore habitat preferences, and slow reproductive rate render it susceptible to overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
. Although specific data is lacking, significant declines in overall ray catches have been documented within its range, including in the Gulf of Thailand
Gulf of Thailand
The Gulf of Thailand , also known in to Malays as Teluk Siam literally meant Gulf of Siam, is a shallow arm of the South China Sea.-Geography:...
, the Arafura Sea, and off Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
. Habitat degradation also threatens this species: over 30% of the mangroves in Indonesia and Malaysia have been cleared since 1980, while pollution
Water pollution
Water pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....
and destructive fishing practices may have also taken their toll. Australian waters offer the reticulate whipray a refuge from fishing pressure, as there it is not targeted commercially and the installation of Turtle Exclusion Devices (TEDs) have reduced bycatch
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...
mortality. However, there are indications of increasing illegal fishing in Australian territory by Indonesian vessels.