''Rhina ancylostoma'', the bowmouth guitarfish, shark ray or mud skate, 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 ray and a member of 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 ...

Rhinidae. Its evolutionary affinities are not fully resolved, though it may be related to true guitarfishes and skates. This rare species occurs widely in the

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

coastal waters of the western Indo-Pacific, at depths of up to . Highly distinctive in appearance, ''Rhina ancylostoma'' has a wide and thick body with a rounded snout and large shark-like

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

and tail fins. Its mouth forms a W-shaped undulating line, and there are multiple thorny ridges over its head and back. It has a dorsal color pattern of many white spots over a bluish gray to brown background, with a pair of prominent black markings over the

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 ...

s. This large species can reach a length of and weight of . Usually found near the sea floor, ''Rhina ancylostoma'' prefers sandy or muddy areas near underwater structures. It is a strong-swimming

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

of bony fishes,

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

s, and molluscs. This species gives live birth to litters of two to eleven pups, which are nourished during gestation by

yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example ...

. 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 assessed ''Rhina ancylostoma'' as Vulnerable because it is widely caught by

artisanal An artisan (from french: artisan, it, artigiano) is a skilled craft worker who makes or creates material objects partly or entirely by hand. These objects may be functional or strictly decorative, for example furniture, decorative art ...

and

commercial fisheries 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 p ...

for its valuable fins and meat. It is viewed as a nuisance by

trawl Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different speci ...

ers, however, because its bulk and thorny skin cause it to damage netted catches.

Habitat degradation Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

and

destruction Destruction may refer to: Concepts * Destruktion, a term from the philosophy of Martin Heidegger * Destructive narcissism, a pathological form of narcissism * Self-destructive behaviour, a widely used phrase that ''conceptualises'' certain kin ...

pose an additional, significant challenge to this ray's survival. ''Rhina ancylostoma'' adapts well to captivity and is displayed in

public aquarium A public aquarium (plural: ''public aquaria'' or ''public Water Zoo'') is the aquatic counterpart of a zoo, which houses living aquatic animal and plant specimens for public viewing. Most public aquariums feature tanks larger than those kept b ...

Taxonomy and phylogeny

German naturalists

Marcus Elieser Bloch Marcus Elieser Bloch (1723–1799) was a German physician and naturalist who is best known for his contribution to ichthyology through his multi-volume catalog of plates illustrating the fishes of the world. Brought up in a Hebrew-speaking Jewish ...

and

Johann Gottlob Schneider Johann Gottlob Theaenus Schneider (18 January 1750 – 12 January 1822) was a German classicist and naturalist. Biography Schneider was born at Collm in Saxony. In 1774, on the recommendation of Christian Gottlob Heine, he became secretary to ...

described ''Rhina ancylostoma'' in their 1801 ''Systema Ichthyologiae''. Their account was based on a long specimen, now lost, collected off the

Coromandel Coast The Coromandel Coast is the southeastern coastal region of the Indian subcontinent, bounded by the Utkal Plains to the north, the Bay of Bengal to the east, the Kaveri delta to the south, and the Eastern Ghats to the west, extending over an ...

of India. The genus name ''Rhina'' comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''rhinos'' ("snout"); the specific epithet ''ancylostoma'' is derived from the Greek ''ankylos'' ("curved" or "crooked") and ''stoma'' ("mouth"). Although Block and Schneider wrote the epithet as ''ancylostomus'' and that form appears in some literature, most modern sources regard the correct form to be ''ancylostoma''. Other common names for this species include shark ray, mud skate, shortnose mud skate, bow-mouthed angel fish, and bow-mouthed angel shark. The evolutionary relationships between ''Rhina ancylostoma'' and other rays are debated. Morphological evidence generally points to a close relationship between ''Rhina'', '' Rhynchobatus'' and '' Rhynchorhina'', which are a group of rays known as the wedgefishes that also have large, shark-like fins. Morphological analyses have tended to place these two genera basally among rays, though some have them as basal to just the

guitarfish The guitarfish, also referred to as shovelnose rays, are a family, Rhinobatidae, of rays. The guitarfish are known for an elongated body with a flattened head and trunk and small, ray-like wings. The combined range of the various species is trop ...

es (Rhinobatidae) and skates (Rajidae) while others have them basal to all other rays except

sawfish Sawfish, also known as carpenter sharks, are a family of rays characterized by a long, narrow, flattened rostrum, or nose extension, lined with sharp transverse teeth, arranged in a way that resembles a saw. They are among the largest fish ...

es (Pristidae). A 2012 study based on mitochondrial DNA upheld ''Rhina'' and ''Rhynchobatus'' as

sister taxa In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

related to the guitarfishes, but also unexpectedly found that they formed a clade with the sawfishes rather than the skates. Following the description of ''Rhynchorhina'' in 2016, a study of mtDNA found that it is part of the same group and their phylogenetic relationship is ((''Rhynchobatus''+''Rhynchorhina'')+''Rhina''). In terms of classification, Bloch and Schneider originally placed the bowmouth guitarfish in the order Abdominales, a now-obsolete grouping of fishes defined by the positioning of their pelvic fins directly behind the

s. Modern sources have included it variously in the order

Rajiformes Rajiformes is one of the four orders in the superorder Batoidea, flattened cartilaginous fishes related to sharks. Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the hea ...

, Rhinobatiformes, Rhiniformes, or the newly proposed Rhinopristiformes. The placement of the bowmouth guitarfish in the family Rhinidae originates from the group "Rhinae", consisting of ''Rhina'' and ''Rhynchobatus'', in Johannes Müller and

Jakob Henle Friedrich Gustav Jakob Henle (; 9 July 1809 – 13 May 1885) 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 ...

's 1841 ''Systematische Beschreibung der Plagiostomen''. Later authors have also assigned this species to the family Rhinobatidae or Rhynchobatidae. Joseph Nelson, in the 2006 fourth edition of '' Fishes of the World'', placed this species as the sole member of Rhinidae in the order Rajiformes, which is supported by morphological but not molecular data. More recent authorities have placed it in Rhinidae together with ''Rhynchobatus'' and ''Rhynchorhina'', reflecting both genetic data and the morphologically intermediate position of ''Rhynchobatus'' between ''Rhina'' and ''Rhynchorhina''.

Description

''Rhina ancylostoma'' is a heavily built fish growing to long and in weight. The head is short, wide, and flattened with an evenly rounded snout; the front portion of the head, including the medium-sized eyes and large spiracles, is clearly distinct from the body. The long nostrils are transversely oriented and have well-developed skin flaps on their anterior margins. The lower jaw has three protruding lobes that fit into corresponding depressions in the upper jaw. There are around 47 upper and 50 lower tooth rows arranged in winding bands; the teeth are low and blunt with ridges on the crown. The five pairs of ventral

gill slit Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In con ...

s are positioned close to the lateral margins of the head. The body is deepest in front of the two tall and falcate (sickle-shaped)

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...

s. The first dorsal fin is about a third larger than the second and originates over the pelvic fin origins. The second dorsal fin is located midway between the first dorsal and the

caudal 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 ...

. The broad and triangular

s have a deep indentation where their leading margins meet the head. The pelvic fins are much smaller than the pectoral fins, and the anal fin is absent. The tail is much longer than the body and ends in a large, crescent-shaped

; the lower caudal fin lobe is more than half the length of the upper. The entire dorsal surface has a grainy texture from a dense covering of tiny dermal denticles. A thick ridge is present along the midline of the back, which bears a band of sharp, robust thorns. There are also a pair of thorn-bearing ridges in front of the eyes, a second pair running from above the eyes to behind the spiracles, and a third pair on the "shoulders". This species is bluish to brownish gray above, lightening towards the margins of the head and over the pectoral fins. There are prominent white spots scattered over the body and fins, a white-edged black marking above each pectoral fin, and two dark transverse bands atop the head between the eyes. The underside is light gray to white. Young rays are more vividly colored than adults, which are browner with fainter patterning and proportionately smaller spots.

Distribution and habitat

While uncommon, ''Rhina ancylostoma'' is widely distributed in the coastal

waters of the western Indo-Pacific. In the Indian Ocean, it is found from KwaZulu-Natal in South Africa to the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...

(including the

Seychelles Seychelles (, ; ), officially the Republic of Seychelles (french: link=no, République des Seychelles; Creole: ''La Repiblik Sesel''), is an archipelagic state consisting of 115 islands in the Indian Ocean. Its capital and largest city, ...

), across the

Indian subcontinent The Indian subcontinent is a list of the physiographic regions of the world, physiographical region in United Nations geoscheme for Asia#Southern Asia, Southern Asia. It is situated on the Indian Plate, projecting southwards into the Indian O ...

and

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...

(including the

Maldives Maldives (, ; dv, ދިވެހިރާއްޖެ, translit=Dhivehi Raajje, ), officially the Republic of Maldives ( dv, ދިވެހިރާއްޖޭގެ ޖުމްހޫރިއްޔާ, translit=Dhivehi Raajjeyge Jumhooriyyaa, label=none, ), is an archipelag ...

), to Shark Bay in

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 ...

. Its Pacific range extends northward to Korea and southern Japan, eastward to New Guinea, and southward to

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 ...

. Found between deep, this ray spends most of its time near the sea floor but can occasionally be seen swimming in midwater. It favors sandy or muddy

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, and can also be found in the vicinity of 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 shipwrecks.

Biology and ecology

''Rhina ancylostoma'' is a strong swimmer that propels itself with its tail like a shark. It is more active at night and is not known to be territorial. This species feeds mainly on demersal bony fishes such as

croakers Sciaenidae are a family of fish in the order Acanthuriformes. They are commonly called drums or croakers in reference to the repetitive throbbing or drumming sounds they make. The family consists of about 286 to 298 species in about 66 to 70 gene ...

and

s such as crabs and shrimp; bivalves and cephalopods are also consumed. Its bands of flattened teeth allow it to crush hard-shelled prey. Curiously, two ''Rhina ancylostoma'' examined in a 2011

stable isotope The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundanc ...

study were found to have fed on

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

rather than demersal animals, in contrast to previous observations. The

tiger shark The tiger shark (''Galeocerdo cuvier'') is a species of requiem shark and the last extant member of the family Galeocerdonidae. It is a large macropredator, capable of attaining a length over . Populations are found in many tropical and tempera ...

(''Galeocerdo cuvier'') is known to prey on ''Rhina ancylostoma''. The ray is protected by the thorns on its head and back, and it may ram perceived threats.

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 ...

s documented from this species include the

tapeworm Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass is Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cesto ...

s '' Carpobothrium rhinei'', '' Dollfusiella michiae'', '' Nybelinia southwelli'', '' Stoibocephalum arafurense'', and '' Tylocephalum carnpanulatum'', the leech '' Pontobdella macrothela'', the

trematode Trematoda is a class of flatworms known as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive h ...

'' Melogonimus rhodanometra'', the

monogenea Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they have both male and female repro ...

ns '' Branchotenthes robinoverstreeti'' and '' Monocotyle ancylostomae'', and the copepods '' Nesippus vespa'', '' Pandarus cranchii'', and '' P. smithii''. There is a record of a ''Rhina ancylostoma'' being cleaned by bluestreak cleaner wrasses (''Labroides dimidiatus''). Reproduction in ''Rhina ancylostoma'' is

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...

, with the developing embryos sustained to term by

. Adult females have a single functional ovary and

uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...

. The litter size varies between two and eleven pups, and newborns measure long.

Sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definit ...

is attained at lengths of for males and over in females. Females grow larger than males.

Human interactions

Throughout its range, ''Rhina ancylostoma'' is caught incidentally or intentionally by

and

using

s, gillnets, and line gear. The fins are extremely valuable due to their use in

shark fin soup Shark fin soup is a traditional soup or stewed dish served in parts of China, Taiwan, and Southeast Asia. The shark fins provide texture, while the taste comes from the other soup ingredients. It is commonly served at special occasions such as ...

, and are often the only parts of the fish kept and brought to market. However, the meat may also be sold fresh or dried and salted, and it is highly sought after in India. When caught as bycatch in trawls, ''Rhina ancylostoma'' is considered a nuisance because its strength and rough skin make it difficult to handle, and as the heavy ray thrashes in the net it can damage the rest of the catch. In Thailand, the enlarged thorns of this species are used to make bracelets. The

(IUCN) has assessed ''Rhina ancylostoma'' as Critically endangered in 2019, delisted from the vulnerable category, along with many other guitarfish species. It is threatened by fishing and by

habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

and

degradation Degradation may refer to: Science * Degradation (geology), lowering of a fluvial surface by erosion * Degradation (telecommunications), of an electronic signal * Biodegradation of organic substances by living organisms * Environmental degradatio ...

, particularly from

blast fishing Blast fishing, fish bombing, dynamite fishing or grenade fishing is a destructive fishing practice using explosives to stun or kill schools of fish for easy collection. This often illegal practice is extremely destructive to the surrounding e ...

coral bleaching Coral bleaching is the process when corals become white due to various stressors, such as changes in temperature, light, or nutrients. Bleaching occurs when coral polyps expel the zooxanthellae ( dinoflagellates that are commonly referred to as a ...

, and

siltation Siltation, is water pollution caused by particulate Terrestrial ecoregion, terrestrial Clastic rock, clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the ...

. Its numbers are known to have declined substantially in Indonesian waters, where it is one of the large rays targeted by a mostly unregulated gillnet fishery. The IUCN has given this species a regional assessment of

Near Threatened A near-threatened species is a species which has been categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature as that may be vulnerable to endangerment in the near future, but it does not currently qualify f ...

in Australian waters, where it is not a targeted species but is taken as bycatch in bottom trawls. The installation of turtle excluder devices on some Australian trawlers has benefited this species. Since it is rare and faces many conservation threats, ''Rhina ancylostoma'' has been called "the

panda The giant panda (''Ailuropoda melanoleuca''), also known as the panda bear (or simply the panda), is a bear species endemic to China. It is characterised by its bold black-and-white coat and rotund body. The name "giant panda" is sometimes use ...

of the aquatic world". It is a popular subject of

s and fares relatively well, with one individual having lived for seven years in captivity. In 2007, the

Newport Aquarium The Newport Aquarium is an aquarium located in Newport, Kentucky, United States at Newport on the Levee, across the river from Cincinnati. It has 70 exhibits and 14 galleries, including five seamless acrylic tunnels totaling over in length. T ...

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia ...

initiated the world's first captive breeding program for this species. Newport Aquarium announced in January 2014 that the female, "Sweet Pea", had become pregnant and given birth to seven pups. By February 2014, all seven pups had died. On January 7, 2016, Sweet Pea gave birth to nine shark pups which were eating on their own and still gaining weight by February 10, 2016. Newport Aquarium later announced that the pups would be moved into a coral reef exhibit where they can be viewed by the public starting on June 24. The species also bred at the S.E.A. Aquarium in

Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, bor ...

in 2015.

References

{{Taxonbar, from=Q1190545 Rajiformes Fish of the Red Sea Marine fauna of East Africa Fish described in 1801 Taxa named by Marcus Elieser Bloch