Coffin ray
From Wikipedia, the free encyclopedia
| Coffin ray | |
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| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Order: | Torpediniformes |
| Family: | Hypnidae Gill, 1862 |
| Genus: | Hypnos Duméril, 1852 |
| Species: | H. monopterygius |
| Binomial name | |
| Hypnos monopterygius Shaw & Nodder, 1795 |
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| Synonyms | |
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Hypnos subnigrum Duméril, 1852 |
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The coffin ray, Hypnos monopterygius, is a species of small, unusually shaped electric ray endemic to Australia. It is the sole species in the family Hypnidae,[1] which some authors regard as a subfamily (Hypninae) of the family Torpedinidae. The name "coffin ray" comes from the shape of specimens that have been dried out in the sun.[2] Other common names include crampfish, electric ray, numbfish, numbie, short-tail electric ray, and torpedo.[3]
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[edit] Distribution and habitat
The coffin ray is found widely in tropical and warm temperate Australian waters, from Gulf Saint Vincent to Broome, Western Australia, and from Eden, New South Wales to Caloundra, Queensland. There is a gap in the species' range between Gulf Saint Vincent and Eden. It is absent from Victoria and Tasmania. It is most commonly found inshore, buried on sandy or muddy bottoms, though it also occurs up to a depth of 240 meters.[4]
[edit] Description
The coffin ray is small and highly distinctive, shaped like a pear when viewed from above. It has a large pectoral fin disc, as wide as it is long. The head is broad and depressed, with five pairs of small gill slits underneath and a broad, arched mouth.[1] The jaws are very slender, elongate, and protrusible.[5] Adults have over 60 rows of small, 3-cusped teeth in either jaw. Its tail is greatly reduced, short, and slender. The two dorsal fins and the tail fin are small and of similar sizes, all concentrated towards the back of the fish. The paired electric organs are visible through the skin at the base of the pectoral fins. The skin is completely unscaled, without dermal denticles or thorns.[1]
Coffin rays are uniform chocolate brown, reddish brown, grey, sandy or pinkish above, often with sparse irregular darker and lighter spots and blotches. The underside is yellowish, greyish white, or white. It may grow as large as 92 cm long, but most are less than 40 cm. Males attain maturity at 24 cm and reach at least 35 cm, while females reach at least 55 cm.[1]
[edit] Biology
A weak swimmer that moves forward in a jerky, fluttery motion, coffin rays incapacitate their prey using electricity. They feed mainly on bony fishes, and also take crustaceans, molluscs, and worms. They are nocturnal hunters, tending to lie motionless under the sand during the day with only the spiracles showing.[6] Coffin rays often take prey of large size relative to themselves, and individuals have been found that have apparently choked attempting to swallow very large fishes. Coffin rays are sometimes found stranded on shore by the tide, but they can survive outside of water for hours.[1] Reproduction is ovoviviparous, with young measuring 8 to 11 cm long.[7]
[edit] Conservation
The coffin ray is common throughout its range and is not believed to be under threat. Although taken as by-catch by commercial trawlers, the coffin ray's hardiness means it is usually returned to the water alive.[4] They are also caught in lobster traps and are infrequently taken by spear fishing.[1] If stepped on or otherwise disturbed, they can deliver a severe electric shock. However, as long as they are not handled they can be approached closely by divers.[6]
[edit] References
- ^ a b c d e f Compagno, L.J.V. and Last, P.R. (1999). Hypnidae. Coffin rays. p. 1447-1448. In: K.E. Carpenter and V.H. Niem (eds.) FAO identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Rome: Food and Agricultural Organization.
- ^ Aitken, K. (2002). Numbray or Coffin Ray (Hypnos monopterygium) Electric Rays. Hypnidae. Retrieved on November 23, 2008
- ^ "Hypnos monopterygius". FishBase. Ed. Ranier Froese and Daniel Pauly. October 2008 version. N.p.: FishBase, 2008.
- ^ a b Cavanagh, R.D., Kyne, P.M., Fowler, S.L., Musick, J.A., and Bennett, M.B. (2003). The conservation status of Australasian chondrichthyans. Brisbane, Australia: The University of Queensland. ISBN 0-9751041-0-1.
- ^ Hamlett, William C. (1999). Sharks, Skates, and Rays: The Biology of Elasmobranch Fishes. Baltimore and London: JHU Press. ISBN 0-8018604-8-2.
- ^ a b Murch, A. COFFIN RAY. Elasmodiver.com. Retrieved on November 23, 2008
- ^ Lisney, T.J. (2003). "IUCN 2008 Red List - Hypnos monopterygius". http://www.iucnredlist.org/search/details.php/41828/all. Retrieved 2008-10-11.
