| 翻訳と辞書 |
| smalltail shark ： ウィキペディア英語版 |
smalltail shark
The smalltail shark (''Carcharhinus porosus'') is a species of requiem shark, and part of the family Carcharhinidae. It is found in the western Atlantic Ocean, from the northern Gulf of Mexico to southern Brazil. It inhabits shallow waters close to shore, particularly over muddy bottoms around estuaries. It tends to swim low in the water column and forms large aggregations segregated by sex. A slim species generally not exceeding in length, the smalltail shark has a rather long, pointed snout, a broad, triangular first dorsal fin, and a second dorsal fin that originates over the midpoint of the anal fin base. It is plain gray in color, without prominent markings on its fins.
The diet of the smalltail shark consists mainly of bony fishes such as croakers, while crustaceans, cephalopods, and smaller sharks and rays may also be consumed. It is viviparous, meaning the developing embryos are sustained by a placental connection. Females bear litters of two to nine young on a biennial cycle, following an approximately 12-month gestation period. The smalltail shark is often caught as bycatch and may be used for meat, fins, liver oil, cartilage, and fishmeal. The impact of fishing on its population is largely unknown except off northern Brazil, where it seems to have declined significantly since the 1980s. Therefore, the International Union for Conservation of Nature has listed it as Data Deficient overall and as Vulnerable in Brazil.
==Taxonomy and phylogeny==
Italian naturalist Camillo Ranzani published the first scientific description of the smalltail shark, in an 1839 volume of ''Novi Commentarii Academiae Scientiarum Instituti Bononiensis''. He named the new shark ''Carcharias porosus'' from the Greek ''porus'' ("pore"), referring to the prominent pores behind its eyes.〔 The type specimen, a -long male from Brazil, has since been lost. This species was moved to the genus ''Carcharhinus'' by later authors.〔 Its Trinidadian name is puppy shark.〔
The evolutionary relationships of the smalltail shark are uncertain. Based on morphology, Jack Garrick in 1982 and Leonard Compagno in 1988 tentatively placed it in a group defined by the whitecheek shark (''C. dussumieri'') and the blackspot shark (''C. sealei'').〔〔 This grouping was equivocally supported by Gavin Naylor's 1992 allozyme-based phylogenetic analysis.〔 Alternately, a 2011 phylogenetic study by Ximena Vélez-Zuazoa and Ingi Agnarsson, based on nuclear and mitochondrial genes, found close relationships between the smalltail shark, the daggernose shark (''Isogomphodon oxyrhynchus''), the blacknose shark (''C. acronotus''), and the finetooth shark (''C. isodon'').〔 The Pacific smalltail shark (''C. cerdale'') was once mistakenly synonymized with ''C. porosus'', until 2011 when José Castro resurrected it as a distinct taxon.〔 An undescribed species closely similar to ''C. porosus'' is known from Southeast Asia.〔
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「smalltail shark」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.
|
|