Longhead catshark
Encyclopedia
The longhead catshark or smoothbelly catshark (Apristurus longicephalus) is a species
of catshark
, family
Scyliorhinidae, with a patchy distribution in the Indo-Pacific
from Mozambique
to southern Japan
to northern Australia
. It is found in water between 500 and 1140 m (1,640.4 and 3,740.2 ft) deep. This species grows to 59 cm (23.2 in) long and is characterized by its extremely long and narrow snout, short abdomen
, and long anal and caudal fins. In addition, a large area of the anterior ventral portion of its body lacks dermal denticles. The longhead catshark is oviparous and the only known cartilaginous fish that is normally hermaphroditic, with the majority of individuals having both the functional reproductive organs of one sex and the undeveloped reproductive organs of the opposite sex. The International Union for Conservation of Nature (IUCN) currently lacks the data to assess the conservation status of this species.
of the longhead catshark was captured in Tosa Bay, Kochi Prefecture
, Japan
on May 12, 1972. The 38 cm (15 in) long specimen was initially thought to be an immature male, but has since been identified as a functionally female hermaphrodite
. The new species was described by Kazuhiro Nakaya in a 1975 volume of the scientific journal
Memoirs of the Faculty of Fisheries, Hokkaido University. In 1999, Nakaya and Sato grouped this species with the similarly long-snouted longfin catshark
(A. herklotsi) in the longicephalus species group
.
region: it is known from the East China Sea
, southern Japan
, the Seychelles
, the Philippines
, Mozambique
, New Caledonia
, and northern Australia
off Townsville
, Ashmore Reef, and North West Cape
. This species inhabits the continental slope at depths of 500–1140 m (1,640.4–3,740.2 ft), and is probably found near the sea floor.
s (protective third eyelids). Behind each eye is a modest spiracle
. The mouth forms a short, wide arch, with well-developed furrows around the corners. The teeth number 36–44 rows in the upper jaw and over 45 rows in either jaw; each tooth is well-spaced from the next and has three or five cusps, with the central cusp much longer than the others. The five pairs of gill slit
s are short, with the fourth and fifth pairs over the base of the pectoral fins.
The first dorsal fin
has a rounded apex and located over the latter third of the pelvic fin bases. The second dorsal fin is similar in shape but much larger than the first, and located over the latter half of the anal fin base. The pectoral fins are moderately large and broad. The medium-sized, rounded pelvic fins are placed fairly close to the pectoral fins. The anal fin is elongated and angular, and separated from the caudal fin by only a deep notch. The narrow caudal fin comprises about one-third of the total length and has a distinct lower lobe and a ventral notch near the tip of the upper lobe. The tiny, well-spaced dermal denticles, each bearing a median ridge and three posterior points, give the skin a velvety texture. A large patch of naked skin extends from the throat and gill region, around the pectoral fins and over the flank and abdomen, to the space between the pelvic and anal fins. Denticles are also absent near the fin margins. This species is dark brown to blackish in color; the naked patches of skin and the interior of the mouth are black.
is not short but almost as long as the spiral valve
intestine
. The function of this trait is unknown, as the feeding habits of this shark have not been documented. The longhead catshark is the only known cartilaginous fish that is normally hermaphroditic: some 85% of the population is functionally male or female, but also possesses undeveloped reproductive organs of the opposite sex (called "rudimentary hermaphroditism"). The factors underlying the evolution of this system have yet to be investigated. This species is oviparous; a single partial egg case has been found, which had tendrils on the posterior corners. Males and females attain sexual maturity
at lengths of around 42–49 cm (16.5–19.3 in) and 51 cm (20.1 in) long respectively.
by deepwater trawl fisheries, though no specific information is available. Thus, the International Union for Conservation of Nature (IUCN) has listed it 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 catshark
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....
, 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...
Scyliorhinidae, with a patchy distribution 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...
from Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
to southern 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...
to 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...
. It is found in water between 500 and 1140 m (1,640.4 and 3,740.2 ft) deep. This species grows to 59 cm (23.2 in) long and is characterized by its extremely long and narrow snout, short abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
, and long anal and caudal fins. In addition, a large area of the anterior ventral portion of its body lacks dermal denticles. The longhead catshark is oviparous and the only known cartilaginous fish that is normally hermaphroditic, with the majority of individuals having both the functional reproductive organs of one sex and the undeveloped reproductive organs of the opposite sex. The International Union for Conservation of Nature (IUCN) currently lacks the data to assess the conservation status of this species.
Taxonomy and phylogeny
The first known specimenHolotype
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...
of the longhead catshark was captured in Tosa Bay, Kochi Prefecture
Kochi Prefecture
is a prefecture of Japan located on the south coast of Shikoku. The capital is the city of Kōchi.- History :Prior to the Meiji Restoration, Kōchi was known as Tosa Province and was controlled by the Chosokabe clan in the Sengoku period and the Yamauchi family during the Edo period.- Geography...
, 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...
on May 12, 1972. The 38 cm (15 in) long specimen was initially thought to be an immature male, but has since been identified as a functionally female hermaphrodite
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
. The new species was described by Kazuhiro Nakaya in a 1975 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...
Memoirs of the Faculty of Fisheries, Hokkaido University. In 1999, Nakaya and Sato grouped this species with the similarly long-snouted longfin catshark
Longfin catshark
The longfin catshark, Apristurus herklotsi, is a cat shark of the family Scyliorhinidae found in the western Pacific from Japan, the Philippines, East and South China seas, and the Kyūshū-Palau Ridge, at depths of between 530 and 865 m. Its length is up to 48 cm....
(A. herklotsi) in the longicephalus species group
Species group
A species group is an informal taxonomic rank into which an assemblage of closely related species within a genus are grouped because of their morphological similarities and their identity as a biological unit with a single monophyletic origin.-Use:...
.
Distribution and habitat
Records of the longhead catshark are patchy and widely spread 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...
region: it is known from the East China Sea
East China Sea
The East China Sea is a marginal sea east of China. It is a part of the Pacific Ocean and covers an area of 1,249,000 km² or 750,000 square miles.-Geography:...
, southern 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...
, the Seychelles
Seychelles
Seychelles , officially the Republic of Seychelles , is an island country spanning an archipelago of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....
, the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
, New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
, 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...
off Townsville
Townsville, Queensland
Townsville is a city on the north-eastern coast of Australia, in the state of Queensland. Adjacent to the central section of the Great Barrier Reef, it is in the dry tropics region of Queensland. Townsville is Australia's largest urban centre north of the Sunshine Coast, with a 2006 census...
, Ashmore Reef, and North West Cape
North West Cape
North West Cape is a large peninsula of land in the north west coast of Western Australia. Cape Range runs down the spine of the peninsula and Ningaloo Reef runs along the western edge...
. This species inhabits the continental slope at depths of 500–1140 m (1,640.4–3,740.2 ft), and is probably found near the sea floor.
Description
Reaching a length of 59 cm (23.2 in), the longhead catshark has a soft, very thin body and a long head comprising one-quarter of the total length. The flattened, bell-shaped snout measures roughly 12% of the total length and narrows considerably in front of the nostrils. The oblique nostrils are divided into large, oval incurrent and excurrent openings by triangular flaps of skin on their anterior rims. The small, horizontally oval eyes are somewhat upward-facing, and equipped with rudimentary nictitating membraneNictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
s (protective third eyelids). Behind each eye is a modest spiracle
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...
. The mouth forms a short, wide arch, with well-developed furrows around the corners. The teeth number 36–44 rows in the upper jaw and over 45 rows in either jaw; each tooth is well-spaced from the next and has three or five cusps, with the central cusp much longer than the others. 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 short, with the fourth and fifth pairs over the base of the pectoral fins.
The first 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...
has a rounded apex and located over the latter third of the pelvic fin bases. The second dorsal fin is similar in shape but much larger than the first, and located over the latter half of the anal fin base. The pectoral fins are moderately large and broad. The medium-sized, rounded pelvic fins are placed fairly close to the pectoral fins. The anal fin is elongated and angular, and separated from the caudal fin by only a deep notch. The narrow caudal fin comprises about one-third of the total length and has a distinct lower lobe and a ventral notch near the tip of the upper lobe. The tiny, well-spaced dermal denticles, each bearing a median ridge and three posterior points, give the skin a velvety texture. A large patch of naked skin extends from the throat and gill region, around the pectoral fins and over the flank and abdomen, to the space between the pelvic and anal fins. Denticles are also absent near the fin margins. This species is dark brown to blackish in color; the naked patches of skin and the interior of the mouth are black.
Biology and ecology
The longhead catshark is unique among Apristurus species in that the duodenumDuodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...
is not short but almost as long as the spiral valve
Spiral valve
A spiral valve is the lower portion of the intestine of some sharks, rays, skates and bichirs. A modification of the ileum, the spiral valve is internally twisted or coiled to increase the surface area of the intestine, to increase nutrient absorption....
intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
. The function of this trait is unknown, as the feeding habits of this shark have not been documented. The longhead catshark is the only known cartilaginous fish that is normally hermaphroditic: some 85% of the population is functionally male or female, but also possesses undeveloped reproductive organs of the opposite sex (called "rudimentary hermaphroditism"). The factors underlying the evolution of this system have yet to be investigated. This species is oviparous; a single partial egg case has been found, which had tendrils on the posterior corners. Males and females attain sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
at lengths of around 42–49 cm (16.5–19.3 in) and 51 cm (20.1 in) long respectively.
Human interactions
The longhead catshark is 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...
by deepwater trawl fisheries, though no specific information is available. Thus, the International Union for Conservation of Nature (IUCN) has listed it 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...
.