Blind shark
| Blind shark Temporal range:
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|---|---|
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| OffNelson Bay, New South Wales | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Subdivision: | Selachimorpha |
| Order: | Orectolobiformes |
| Family: | Brachaeluridae |
| Genus: | Brachaelurus |
| Species: | B. waddi
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| Binomial name | |
| Brachaelurus waddi (Bloch&J. G. Schneider,1801)
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| Range of the blind shark | |
| Synonyms | |
|
Chiloscyllium furvumMacleay, 1881 | |
Theblind shark(Brachaelurus waddi) is one of twospeciesofcarpet sharksin thefamilyBrachaeluridae,along with thebluegrey carpetshark(Brachaelurus colcloughi). Found along the coast of easternAustralia,thisnocturnal,bottom-dwellingspecies is common in rocky areas andseagrassbeds from theintertidal zoneto a depth of 140 m (460 ft). It often roams intidal poolswhere it may be trapped by the receding tide, and can survive for an extended period out of water.
Maturingat under 62–66 cm (24–26 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 largepectoral fins,two nearly equal-sizeddorsal finsplaced far back on the body, and ananal finplaced close to thecaudal fin.The blind shark feeds primarily on smallinvertebratesandbony fishes.It isaplacental viviparouswith 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 eithercommercialorrecreational fishers,and its hardiness means thatincidentally caughtindividuals are likely to be returned to the water alive. In the absence of substantial threats to its population, theInternational Union for Conservation of Naturehas assessed it as ofLeast Concern.
Taxonomy and phylogeny
[edit]GermannaturalistsMarcus Elieser BlochandJohann Gottlob Schneideroriginally described the blind shark asSqualus waddi,in their 1801Systema Ichthyologiae.However, there is uncertainty over whether their account was referring to this species or thebrownbanded bamboo shark(Chiloscyllium punctatum), as it was based on a painting byJohn Lathamthat could not be located by subsequent authors. In 1907,James Douglas Ogilbycoined the genusBrachaelurusfor this species, from the Greekbrachysmeaning "short", andailourosmeaning "cat".[3]In 1973,Leonard Compagnoplaced it and the bluegrey carpetshark in their own family.[4]This shark may also be referred to as the brown catshark or dusky dogfish.[5]
Variousphylogeneticstudies, based onmorphology,have concluded that the blind shark lineage represents the sistertaxonto thewobbegongs.[6]Blind sharkfossilshave been found inLate Cretaceousperiod(99.6–65.5Ma) deposits fromEurope,as well as inPlioceneepoch(5.3–2.6 Ma) deposits fromChileandPeru.A number of otherBrachaelurusspecies are also known from the fossil record.[1]
Distribution and habitat
[edit]
The range of the blind shark is restricted to the eastern coast ofAustralia,fromMooloolabain southernQueenslandtoJervis BayinNew South Wales;past reports from offWestern AustraliaandNorthern Territoryappear to be misidentifications of the brownbanded bamboo shark.[2]The blind shark is abottom-dwellingspecies that generally inhabits thecontinental shelffrom theintertidal zone,includingtidal poolsbarely deep enough to cover its body, to a depth of 73 m (240 ft), though it has been recorded as deep as 140 m (460 ft).[4][5]Preferred habitats are rocky areas and adjacentseagrassbeds; juveniles are common in high-energy surge zones.[2]InNelson Bay,this shark has been observed lying in the open atopsponges.[7]
Description
[edit]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 ovalspiraclesare positioned behind and below and have obvious raised rims. Thenostrilsare 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 ofgill slitsare small, with the fifth pair close to the fourth.[4][8]
Thepectoral finsare large and broad, with rounded margins. The twodorsal finsare roughly equal in size and have rounded apices and angular free rear tips; the first dorsal fin originates over the bases of thepelvic fins.The pelvic fins are rounded and almost as large as the pectoral fins. Theanal finis less than half the size of the dorsal fins and is positioned very close to the base of the long, lowcaudal 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. Thedermal denticlesare large, giving the skin a rough texture.[4][8]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.[9]The blind shark can reach a length of 0.9–1.2 m (3.0–3.9 ft), though most are much smaller.[4]
Biology and ecology
[edit]Contrary to itscommon name,the blind shark has "perfectly adequate" vision.[10]It was so named by anglers because it retracts itseyeballsand shuts its thick lowereyelidswhen removed from the water.[4]This species can live for up to 18 hours out of water, allowing it to survive being stranded by the outgoing tide.[9]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 andseagrass meadowsto forage for smallinvertebrates(includingcrabs,shrimp,cephalopods,andsea anemones) andbony fishes.Prey items are captured via suction.[2][4]
The blind shark isaplacental viviparouswith a possibly annual reproductive cycle.[2]Females give birth to 7–8 pups during the summer; newborns measure 15–18 cm (5.9–7.1 in) long.Sexual maturityis attained at under a length of 62 cm (24 in) for males, and 66 cm (26 in) for females.[4]It has lived to 20 years old in captivity.[10]A knownparasiteof this shark is an undescribed species oftapewormin the genusCarpobothrium.[11]
Human interactions
[edit]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.[8][9]There are cases of blind sharks biting and holding onto divers'wetsuitseven after they surfaced, and could only be removed by prying open the sharks' jaws.[7]This species is one of the few sharks considered suitable forprivate aquaria,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 theSydney Aquariumhaving successfully maintained a breeding colony.[10]
Commercial fisheriesdo not target or utilize the blind shark, as its flesh has a strongammonia-like taste that is not easily removed. It iscaught incidentallybyprawntrawland 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 byrecreational fishers,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 toshark netsused to protect beaches. The impact of collection for the aquarium trade on this shark is unknown but not thought to be severe.[2][4]TheInternational Union for Conservation of Nature(IUCN) has listed the blind shark underLeast Concern,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 proposedMarine Protected Areas(MPAs).[2]
See also
[edit]References
[edit]- ^abWilliams, G.S. (1999).A Listing of Fossil Sharks and Rays of the World.Retrieved 30 January 2010.
- ^abcdefgKyne, P.M.; Bennett, M.B. (2015)."Brachaelurus waddi".IUCN Red List of Threatened Species.2015:e.T41732A68610784.doi:10.2305/IUCN.UK.2015-4.RLTS.T41732A68610784.en.Retrieved12 November2021.
- ^Ogilby, J.D. (25 August 1908). "On new genera and species of fishes".Proceedings of theRoyal Society of Queensland21:1–26.
- ^abcdefghiCompagno, L.J.V. (2002).Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date (Volume 2).Rome: Food and Agriculture Organization of the United Nations. pp. 142–146ISBN92-5-104543-7.
- ^abFroese, Rainer; Pauly, Daniel (eds.) (2010)."Brachaelurus waddi"inFishBase.January 2010 version.
- ^Goto, T. (2001). "Comparative Anatomy, Phylogeny and Cladistic Classification of the Order Orectolobiformes (Chondrichthyes, Elasmobranchii)".Memoirs of the Graduate School of Fisheries Science, Hokkaido University48(1): 1–101.
- ^abMurch, A.Blind Shark -Brachaelurus waddiinformation.Elasmodiver.Retrieved 31 January 2010.
- ^abcLast, P.R. and J.D. Stevens (2009).Sharks and Rays of Australia(second ed). Harvard University Press. pp. 131.ISBN0-674-03411-2.
- ^abcMichael, S.W. (1993).Reef Sharks & Rays of the World.Sea Challengers. p. 40.ISBN0-930118-18-9.
- ^abcMichael, S.W. "Sharks at Home".Aquarium Fish MagazineMarch 2004: pp. 20–29.
- ^Caira, J.N., K. Jensen and C.J. Healy (1999). "On the phylogenetic relationships among tetraphyllidean, lecanicephalidean and diphyllidean tapeworm genera".Systematic Parasitology42:77–151.