Blind shark
Encyclopedia
The blind shark is one of two species
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 carpet shark
Carpet shark
The carpet sharks are an order, Orectolobiformes, of sharks, so called because many members have ornate patterns reminiscent of carpets....

s in the 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...

 Brachaeluridae
Brachaeluridae
The Brachaeluridae, or blind sharks, are a small family of sharks in the order Orectolobiformes. There are only two species of blind shark, both of which are native to shallow coastal waters up to depth, off the eastern coast of Australia....

, along with the bluegrey carpetshark (Heteroscyllium colcloughi), and the only extant member of its genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

. Found along the coast of eastern 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...

, this nocturnal, bottom-dwelling species is common in rocky areas and 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:...

 beds 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 a depth of 140 m (459.3 ft). It often roams in tidal pools where it may be trapped by the receding tide, and can survive for an extended period out of water. The blind shark is not actually blind; its 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...

 came from its habit of closing its eyes when taken out of the water.

Maturing at under 62–66 cm (24.4–26 in) long, the blind shark has a stocky, grayish to brownish body with white flecks and darker bands that fade with age. Its head is wide, flattened, and blunt, with small eyes on top and a pair of long barbels underneath. It has large pectoral fins, two nearly equal-sized 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 placed far back on the body, and an anal fin placed close to the caudal fin. The blind shark feeds primarily on small 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. It is aplacental viviparous with females bearing litters of 7–8 pups in the summer. This small shark adapts readily to being kept in captivity. It is not valued by either commercial
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...

 or recreational fishers
Recreational 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....

, and its hardiness means that incidentally caught
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...

 individuals are likely to be returned to the water alive. In the absence of substantial threats to its population, the International Union for Conservation of Nature has assessed it as of Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...

.

Taxonomy and phylogeny

German naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...

s Marcus Elieser Bloch
Marcus Elieser Bloch
Marcus Elieser Bloch was a German medical doctor and naturalist. He is generally considered one of the most important ichthyologists of the 18th century.- Life :...

 and Johann Gottlob Schneider
Johann Gottlob Schneider
Johann Gottlob Theaenus Schneider was a German classicist and naturalist.-Biography:Schneider was born at Collm in Saxony...

 originally described the blind shark as Squalus waddi, in their 1801 Systema Ichthyologiae. However, there is uncertainty over whether their account was referring to this species or the brownbanded bamboo shark
Brownbanded bamboo shark
The brownbanded bamboo shark, Chiloscyllium punctatum, is a bamboo shark in the family Hemiscylliidae found in the Indo-West Pacific from Japan to northern Australia, between latitudes 34° N and 26° S, to depths of . Its length is up to...

 (Chiloscyllium punctatum), as it was based on a painting by John Latham
John Latham (ornithologist)
John Latham was an English physician, naturalist and author. He was born at Eltham in Kent, and was the eldest son of John Latham, a surgeon there, and his mother was a descendant of the Sothebys, in Yorkshire....

 that could not be located by subsequent authors. In 1907, James Douglas Ogilby
James Douglas Ogilby
James Douglas Ogilby was an Australian ichthyologist.Ogilby was born in Belfast, Ireland, and was the son of zoologist William Ogilby. He received his education at Winchester College, England, and Trinity College, Dublin.Ogilby worked for the British Museum before joining the Australian Museum in...

 coined the genus Brachaelurus for this species, from the Greek brachys meaning "short", and ailouros meaning "cat". In 1973, Leonard Compagno
Leonard Compagno
Leonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organization of the United Nations.-Career:*Ph.D,...

 placed it and the bluegrey carpetshark in their own family. This shark may also be referred to as the brown catshark or dusky dogfish.

Various phylogenetic studies, based on morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

, have concluded that the blind shark lineage represents the sister taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

 to the wobbegong
Wobbegong
Wobbegong is the common name given to the 12 species of carpet sharks in the family Orectolobidae. They are found in shallow temperate and tropical waters of the western Pacific Ocean and eastern Indian Ocean, chiefly around Australia and Indonesia, although one species occurs as far north as Japan...

s. Blind shark fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s have been found in Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 period (99.6–65.5 Ma) deposits from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, as well as in Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

 epoch
Epoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...

 (5.3–2.6 Ma) deposits from Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

 and Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

. A number of other Brachaelurus species are also known from the fossil record.

Distribution and habitat

The range of the blind shark is restricted to the eastern coast of 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...

, from Mooloolaba in southern Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...

 to Jervis Bay
Jervis Bay
Jervis Bay is a large bay bounded by the state of New South Wales, the Jervis Bay Territory, and a detached enclave of the Australian Capital Territory. HMAS Creswell is located between Jervis Bay Village and Greenpatch in the Jervis Bay Territory.-History:...

 in New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

; past reports from off 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...

 and Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...

 appear to be misidentifications of the brownbanded bamboo shark. The blind shark is a bottom-dwelling species that generally inhabits the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...

 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...

, including tidal pools barely deep enough to cover its body, to a depth of 73 m (239.5 ft), though it has been recorded as deep as 140 m (459.3 ft). Preferred habitats are rocky areas and adjacent 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:...

 beds; juveniles are common in high-energy surge zones. In Nelson Bay, this shark has been observed lying in the open atop sponges.

Description

The blind shark has a stocky body and a wide, somewhat flattened head with a blunt snout. The small, oval eyes are situated high on the head and have strong ridges underneath; the oval 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...

s are positioned behind and below and have obvious raised rims. The 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 are placed almost at the tip of the snout and have long, tapering barbels in front and well-developed skin flaps and grooves around the incurrent openings. A pair of obvious grooves connect the nostrils to the small, almost transverse mouth. There are 32–34 upper tooth rows and 21–29 lower tooth rows; each tooth has an upright, awl-shaped central cusp and a pair of lateral cusplets. 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 small, with the fifth pair close to the fourth.

The pectoral fins are large and broad, with rounded margins. 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 roughly equal in size and have rounded apices and angular free rear tips; the first dorsal fin originates over the bases of the pelvic fins. The pelvic fins are rounded and almost as large as the pectoral fins. The anal fin is less than half the size of the dorsal fins and is positioned very close to the base of the long, low caudal fin. The caudal fin comprises about a quarter of the total length, with no ventral lobe and a strong ventral notch near the tip of the upper lobe. The dermal denticles are large, giving the skin a rough texture. This species is light to dark brown above, often with white flecks, and lighter below. Juveniles also have dark bands over the body and tail, which fade with age. The blind shark can reach a length of 0.9–1.2 m (3–3.9 ft), though most are much smaller.

Biology and ecology

Contrary to its 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...

, the blind shark has "perfectly adequate" vision. It was so named by anglers because it retracts its eyeballs and shuts its thick lower eyelid
Eyelid
An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily...

s when removed from the water. This species can live for up to 18 hours out of water, allowing it to survive being stranded by the outgoing tide. The blind shark is secretive and sluggish during the day, with adults usually hiding in caves or under ledges and juveniles inside crevices, though it will take food given the opportunity. At night, it moves out over reefs and seagrass meadows to forage for small 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 (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...

, cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s, and sea anemone
Sea anemone
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...

s) and bony fishes. Prey items are captured via suction.
The blind shark is aplacental viviparous with a possibly annual reproductive cycle. Females give birth to 7–8 pups during the summer; newborns measure 15–18 cm (5.9–7.1 in) long. 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...

 is attained at under a length of 62 cm (24.4 in) for males, and 66 cm (26 in) for females. It has lived to 20 years old in captivity. A known parasite of this shark is an undescribed species of tapeworm in the genus Carpobothrium.

Human interactions

The blind shark is basically harmless to humans, though it can bite if provoked and is difficult to remove, owing to its strong jaws and powerful suction. There are cases of blind sharks biting and holding onto divers' wetsuit
Wetsuit
A wetsuit is a garment, usually made of foamed neoprene, which is worn by surfers, divers, windsurfers, canoeists, and others engaged in water sports, providing thermal insulation, abrasion resistance and buoyancy. The insulation properties depend on bubbles of gas enclosed within the material,...

s even after they surfaced, and could only be removed by prying open the sharks' jaws. This species is one of the few sharks considered suitable for private aquaria
Fishkeeping
Fishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond. There is also a fishkeeping industry, as a branch of agriculture.-Types of fishkeeping systems:...

, as it is hardy, grows to a small size, and has sedentary habits, though its nocturnal, reclusive nature make it difficult to observe. The blind shark has even been induced to breed in captivity, with the Sydney Aquarium
Sydney Aquarium
Sydney Aquarium is a public aquarium located in the city of Sydney, New South Wales, Australia. It is located on the eastern side of Darling Harbour to the north of the Pyrmont Bridge...

 having successfully maintained a breeding colony.

Commercial fisheries
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...

 do not target or utilize the blind shark, as its flesh has a strong ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

-like taste that is not easily removed. It is caught incidentally
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...

 by 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...

 trawl and other fisheries off Queensland and New South Wales, though post-discard survival may be high due to its ability to tolerate being out of water. Small numbers of blind sharks are caught by recreational fishers
Recreational 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 regard them as a nuisance because its small mouth and strong jaws make removing lodged hooks difficult. It is generally too small to be susceptible to shark net
Shark net
A shark net is a submerged net placed around beaches to reduce shark attacks on swimmers.Shark nets do not offer complete protection but work on the principle of "fewer sharks, fewer attacks". They reduce occurrence via shark mortality. Reducing the local shark populations is believed to reduce the...

s used to protect beaches. The impact of collection for the aquarium trade on this shark is unknown but not thought to be severe. The International Union for Conservation of Nature (IUCN) has listed the blind shark under Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...

, as it remains abundant and the various pressures on its population do not seem to pose significant threats. Its range overlaps a number of current and proposed Marine Protected Area
Marine Protected Area
Marine Protected Areas, like any protected area, are regions in which human activity has been placed under some restrictions in the interest of conserving the natural environment, it's surrounding waters and the occupant ecosystems, and any cultural or historical resources that may require...

s (MPAs).
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK