Indonesian angelshark
Encyclopedia
The Indonesian angelshark (Squatina legnota) is a rare species
of angel shark
, family
Squatinidae, known only from a few specimens collected from fish landing sites in southern Indonesia
. It is thought to inhabit the deep waters of the continental slope. Reaching at least 1.34 m (4.4 ft) long, this species has a flattened, ray
-like shape and a well-developed tail and caudal fin. It is characterized by the absences of fringes on its nasal barbels and thorns down the midline of its back, as well as by its relatively plain grayish-brown dorsal coloration with dark saddles beneath the dorsal fin
bases and a black leading margin on the underside of the pectoral fins. The International Union for Conservation of Nature (IUCN) presently lacks sufficient information to assess the conservation status of this species.
(CSIRO) researchers Peter Last and William White in a 2008 volume of the scientific journal
Zootoxa, based on specimens found at several Indonesia
n fish landing sites. One of the specimens, a 47 cm (18.5 in) long female from the Cilacap
landing site in central Java
, was designated the holotype
. The specific epithet comes from the Greek
legnotos ("having a colored border"), in reference to the dark leading margins of the pectoral fins.
Björn Stelbrink and colleagues' 2010 phylogenetic analysis, based on mitochondrial DNA
, found that the sister species of the Indonesian angelshark is the Taiwan angelshark
(S. formosa); the two were the closest genetically of all the species examined. The pair additionally formed a clade
with the Japanese angelshark (S. japonica) and the ocellated angelshark
(S. tergocellatoides), both also Asian species.
, Cilacap in Central Java
, Kedonganan in Bali
, and Tanjung Luar in Lombok
. Therefore, specific information on its preferred natural habitat
is unavailable, though it is probably bottom-dwelling in the deeper waters of the continental slope.
s. The nostrils are large and preceded by well-developed flaps of skin that reach the mouth; each flap bears two prominent barbels, which are smooth rather than fringed. The capacious, gently curved mouth is placed at the front of the head. There are long, deep furrows extending from the mouth corners onto and away from the lower jaw. The teeth number around 18 rows in both jaws; each is small and dagger-like, with a single sharp cusp. The five pairs of gill slit
s are long and placed on the sides of the head.
The pectoral fins are angular, with the anterior lobes of their bases free from the head, and their outer tips forming an angle of slightly under 120°. The tips of the pelvic fins are rounded; males have thick claspers. The two dorsal fin
s are close in shape and size, with rounded to angular apexes and slightly convex trailing margins. The first dorsal originates over the pelvic fins rear tips, and the second dorsal is placed close to the first. There is no anal fin. The tail is rather long, with the caudal peduncle moderately flattened and expanded laterally into keels. The lower lobe of the short and triangular caudal fin is larger than the upper, and there is a notch in the upper lobe trailing margin. The dorsal surface is covered by small, roughly conical dermal denticles. This species is grayish brown above, darkening around the eyes and on the snout and becoming translucent at the trailing fin margins. There are blackish saddle markings below the dorsal fin bases, and sometimes also large, dark blotches and "eyespots" scattered over the dorsal surface. The underside is almost completely white, with a black leading margin on the pectoral fins.
on demersal longlines and marketed for meat and fins. If the presently limited Indonesian deepwater fisheries were to expand, this species may be threatened as other angel shark species have shown themselves to be particularly susceptible to fishing depletion. Pending more data, the International Union for Conservation of Nature has listed this shark under Data Deficient
.
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 angel shark
Angel shark
The angel sharks are an unusual genus of sharks with flattened bodies and broad pectoral fins that give them a strong resemblance to rays. The more than 16 known species are in the genus Squatina, the only genus in its family, Squatinidae, and order Squatiniformes. They occur worldwide in temperate...
, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Squatinidae, known only from a few specimens collected from fish landing sites in southern 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...
. It is thought to inhabit the deep waters of the continental slope. Reaching at least 1.34 m (4.4 ft) long, this species has a flattened, ray
Batoidea
Batoidea is a superorder of cartilaginous fish commonly known as rays and skates, containing more than 500 described species in thirteen families...
-like shape and a well-developed tail and caudal fin. It is characterized by the absences of fringes on its nasal barbels and thorns down the midline of its back, as well as by its relatively plain grayish-brown dorsal coloration with dark saddles beneath the dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
bases and a black leading margin on the underside of the pectoral fins. The International Union for Conservation of Nature (IUCN) presently lacks sufficient information to assess the conservation status of this species.
Taxonomy and phylogeny
The Indonesian angelshark was described by Commonwealth Scientific and Industrial Research OrganisationCommonwealth Scientific and Industrial Research Organisation
The Commonwealth Scientific and Industrial Research Organisation is the national government body for scientific research in Australia...
(CSIRO) researchers Peter Last and William White in a 2008 volume of the scientific journal
Scientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
Zootoxa, based on specimens found at several 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 fish landing sites. One of the specimens, a 47 cm (18.5 in) long female from the Cilacap
Cilacap
Cilacap is a regency in the southwestern part of Central Java province in Indonesia. Its capital is Cilacap, which is an municipality in its own right....
landing site in central Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west Java...
, was designated the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
. The specific epithet comes from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
legnotos ("having a colored border"), in reference to the dark leading margins of the pectoral fins.
Björn Stelbrink and colleagues' 2010 phylogenetic analysis, based on mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
, found that the sister species of the Indonesian angelshark is the Taiwan angelshark
Taiwan angelshark
The Taiwan angelshark, Squatina formosa, is an angel shark of the family Squatinidae found around Taiwan between latitudes 24° N and 22° N, at depths of between 185 and 220 m...
(S. formosa); the two were the closest genetically of all the species examined. The pair additionally formed a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
with the Japanese angelshark (S. japonica) and the ocellated angelshark
Ocellated angelshark
The ocellated angelshark, Squatina tergocellatoides, is an angel shark of the family Squatinidae found only from the Taiwan Straits in the western Pacific between latitudes 28° N and 22° N and in northern Malaysia...
(S. tergocellatoides), both also Asian species.
Distribution and habitat
The known specimens of the Indonesian angelshark have come from fish landing sites at Palabuhanratu in West JavaWest Java
West Java , with a population of over 43 million, is the most populous and most densely populated province of Indonesia. Located on the island of Java, it is slightly smaller in area than densely populated Taiwan, but with nearly double the population...
, Cilacap in Central Java
Central Java
Central Java is a province of Indonesia. The administrative capital is Semarang. It is one of six provinces on the island of Java.This province is the province of high Human Development in Indonesia and its Points Development Index countries is equivalent to Lebanon. The province of Central Java...
, Kedonganan in Bali
Bali
Bali is an Indonesian island located in the westernmost end of the Lesser Sunda Islands, lying between Java to the west and Lombok to the east...
, and Tanjung Luar in Lombok
Lombok
Lombok is an island in West Nusa Tenggara province, Indonesia. It forms part of the chain of the Lesser Sunda Islands, with the Lombok Strait separating it from Bali to the west and the Alas Strait between it and Sumbawa to the east...
. Therefore, specific information on its preferred natural 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...
is unavailable, though it is probably bottom-dwelling in the deeper waters of the continental slope.
Description
The largest known Indonesian angelshark specimen measured 1.34 m (4.4 ft) long. As in all angel sharks, it has a flattened body with greatly enlarged pectoral and pelvic fins. The broad, flattened head has a very short, blunt snout and small, widely spaced eyes placed somewhat on top. The eyes are followed by much larger, crescent-shaped spiracleSpiracle
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. The nostrils are large and preceded by well-developed flaps of skin that reach the mouth; each flap bears two prominent barbels, which are smooth rather than fringed. The capacious, gently curved mouth is placed at the front of the head. There are long, deep furrows extending from the mouth corners onto and away from the lower jaw. The teeth number around 18 rows in both jaws; each is small and dagger-like, with a single sharp cusp. The five pairs of gill slit
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, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
s are long and placed on the sides of the head.
The pectoral fins are angular, with the anterior lobes of their bases free from the head, and their outer tips forming an angle of slightly under 120°. The tips of the pelvic fins are rounded; males have thick claspers. The two dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s are close in shape and size, with rounded to angular apexes and slightly convex trailing margins. The first dorsal originates over the pelvic fins rear tips, and the second dorsal is placed close to the first. There is no anal fin. The tail is rather long, with the caudal peduncle moderately flattened and expanded laterally into keels. The lower lobe of the short and triangular caudal fin is larger than the upper, and there is a notch in the upper lobe trailing margin. The dorsal surface is covered by small, roughly conical dermal denticles. This species is grayish brown above, darkening around the eyes and on the snout and becoming translucent at the trailing fin margins. There are blackish saddle markings below the dorsal fin bases, and sometimes also large, dark blotches and "eyespots" scattered over the dorsal surface. The underside is almost completely white, with a black leading margin on the pectoral fins.
Biology and ecology
Little is known of the Indonesian angelshark's natural history. It is presumably aplacental viviparous like other members of its family. The smallest male specimen, an adult, measured 1.25 m (4.1 ft) long.Human interactions
The Indonesian angelshark is rarely caught incidentallyBycatch
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...
on demersal longlines and marketed for meat and fins. If the presently limited Indonesian deepwater fisheries were to expand, this species may be threatened as other angel shark species have shown themselves to be particularly susceptible to fishing depletion. Pending more data, the International Union for Conservation of Nature has listed this shark under Data Deficient
Data Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...
.