The frilled shark, Chlamydoselachus anguineus, is a species of deep-sea shark in the family Chlamydoselachidae, regarded as a "living fossil". It was long thought to be the only member of its family, until in 2009 frilled sharks off southern Africa were described as a separate species, C. africana. These species are very different from the other hexanchiform sharks, and it has recently been proposed that the two frilled sharks should be given their own order, Chlamydoselachiformes. Additional extinct types are known from fossil teeth. The frilled shark was thought to be extinct itself; it was only discovered alive in Japanese waters in the 19th century.[2] On January 21, 2007, a specimen was found alive off the coast of Japan near the Awashima Marine Park in Shizuoka, southwest of Tokyo. The shark was captured but was not adapted to live in the warm, shallow water that it was moved to. The specimen died soon after capture. [3]
[edit] Appearance
Superficially, the frilled shark resembles a dark brown or grey eel, but the six gill slits identify it as a shark. The tissue of the gill slits protrudes somewhat, thus inspiring the common name. Its dorsal fin is small, anal fin large, and the caudal fin (tail fin) is highly asymmetric, the dorsal part almost unnoticeable. Its teeth are small, tricuspid, and very sharp. Mature males can grow to be 1-1.1 m (3.2-3.6 ft) in length, whereas females can grow to be 1.4-1.5 m (4.4-4.9 ft).[4] It has been recorded at up to 2 m (6.5 ft) in length.
[edit] Distribution
Distribution is worldwide, but they are very rarely found in shallow water. They have been reported in all oceans but are mainly found near Norway, South Africa, New Zealand, and Chile. The sharks are usually found at depths of between 50 m and 1,500 m. They typically eat squid, other sharks, and deepwater bony fish.[5] The frilled shark is sometimes referred to as a living fossil partially because the species has changed little since pre-historic times.[6]
[edit] Reproduction
Reproduction is not well-understood, but like many other sharks they bear live young (ovoviviparous), with litter sizes of 2 to 12 pups, although the average is six pups. Frilled sharks have the longest gestation (pregnancy) period currently known among animals since it remains pregnant for 3.5 years before giving birth.
[edit] Sightings
The first known video footage of a frilled shark in its natural habitat.
Frilled sharks appear regularly in the catches from bottom trawling, and when caught are used as food or for fishmeal.[5]
On January 21, 2007, staff at Awashima Marine Park in Shizuoka, southwest of Tokyo, were alerted by fishermen to a 'strange eel-like fish with needle-like teeth'. The fish was identified as a pregnant female 1.6 m frilled shark and was captured by park staff who were concerned that the shark appeared to be unhealthy. They took it out of the water and put it into a salt water tank where they filmed it and took pictures of it. The shark died a few hours after capture. This rare surface appearance of a frilled shark has been attributed to the animal being unable to live in the warmer temperature water. Living in the colder deep ocean water, it's likely the sharks temperature rose greatly and resulted in its demise.[7]
[edit] See also
[edit] References
- General references
- Paul & Fowler (2003). Chlamydoselachus anguineus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes justification for why this species is near threatened
- Chlamydoselachus anguineus (TSN 159813). Integrated Taxonomic Information System. Retrieved on 23 January 2006.
- Compagno, Dando, & Fowler, Sharks, Collins Gem, HarperCollins, London 2006) ISBN 0-00-721986-5
- Compagno, Dando, & Fowler, Sharks of the World, Princeton University Press, New Jersey 2005 ISBN 0-691-12072-2
- IUCN 2007. 2007 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 28 September 2007.
[edit] External links
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