| 翻訳と辞書 |
| Slender smooth-hound ： ウィキペディア英語版 |
Slender smooth-hound
The slender smooth-hound or gollumshark (''Gollum attenuatus'') is a species of ground shark in the family Pseudotriakidae. It is endemic to the waters around New Zealand, where it is usually found close to the bottom over the continental slope at depths of . An extremely slim, plain brownish shark reaching in length, the slender smooth-hound can be identified by its broad, flattened head with a long, distinctively bell-shaped snout. Its mouth is angular with short furrows at the corners, and contains a very high number of tooth rows in both jaws. Its two dorsal fins are roughly equal in size.
The diet of the slender smooth-hound is diverse, but dominated by small, benthic bony fishes and decapod crustaceans. It exhibits a specialized form of aplacental viviparity with oophagy: the females produce a single capsule in each uterus that contains 30–80 ova, of which one ovum develops into an embryo that consumes the rest of the ova and stores the yolk material in its external yolk sac. The growing embryo is mainly sustained by this yolk sac during gestation, though it may be additionally supplied with histotroph ("uterine milk") produced by the mother. The typical litter size is two pups, one per uterus. The International Union for Conservation of Nature (IUCN) has assessed the slender smooth-hound as Least Concern; it is taken as fishery bycatch but not in great numbers, and furthermore large portions of its range see minimal fishing activity.
==Taxonomy and phylogeny==
The first known specimen of the slender smooth-hound was a long adult male collected by the trawler ''Maimai'' in December 1953, at a depth of off Cape Palliser on New Zealand's North Island. It was preserved by the crew as a curiosity and given to ichthyologist Jack Garrick, who described it in a 1954 issue of the scientific journal ''Transactions of the Royal Society of New Zealand''. Garrick named the species ''Triakis attenuata'', in reference to its extremely slender ("attenuate") body.〔
In 1973, Leonard Compagno proposed a separate genus for the slender smooth-hound: ''Gollum'', after the character in J. R. R. Tolkien's ''The Lord of the Rings'', "to whom this shark bears some resemblance in form and habits."〔 He placed ''Gollum'' with the finback catsharks (Proscylliidae), but also noted its many anatomical similarities to the false catshark (''Pseudotriakis microdon''). At the time, Compagno chose to maintain ''Pseudotriakis'' as the sole member of the family Pseudotriakidae because of its numerous unique traits.〔 More recently, he and other taxonomists have increasingly tended to group ''Gollum'' and ''Pseudotriakis'' together in the family Pseudotriakidae. This arrangement was corroborated by a 2006 phylogenetic study by Juan Andrés López and colleagues, which found that the two genera have a high degree of genetic similarity across four protein-coding genes and form a natural clade apart from ''Proscyllium''.〔 An additional species of ''Gollum'' has now been described,〔 and there is at least one additional species yet to be described.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Slender smooth-hound」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|