|
The hawksbill sea turtle (''Eretmochelys imbricata'') is a critically endangered sea turtle belonging to the family Cheloniidae. It is the only extant species in the genus ''Eretmochelys''. The species has a worldwide distribution, with Atlantic and Indo-Pacific subspecies—''E. i. imbricata'' and ''E. i. bissa'', respectively. The hawksbill's appearance is similar to that of other marine turtles. In general it has a flattened body shape, a protective carapace, and flipper-like arms, adapted for swimming in the open ocean. ''E. imbricata'' is easily distinguished from other sea turtles by its sharp, curving beak with prominent tomium, and the saw-like appearance of its shell margins. Hawksbill shells slightly change colors, depending on water temperature. While this turtle lives part of its life in the open ocean, it spends more time in shallow lagoons and coral reefs. Human fishing practices threaten ''E. imbricata'' populations with extinction. The World Conservation Union classifies the hawksbill as critically endangered.〔 Hawksbill shells were the primary source of tortoiseshell material used for decorative purposes. The Convention on International Trade in Endangered Species outlaws the capture and trade of hawksbill sea turtles and products derived from them.〔 ==Anatomy and morphology== ''E. imbricata'' has the typical appearance of a marine turtle. Like the other members of its family, it has a depressed body form and flipper-like limbs adapted for swimming. Adult hawksbill sea turtles have been known to grow up to in length, weighing around on average. The heaviest hawksbill ever captured was measured to be . The turtle's shell, or carapace, has an amber background patterned with an irregular combination of light and dark streaks, with predominantly black and mottled-brown colors radiating to the sides. Several characteristics of the hawksbill sea turtle distinguish it from other sea turtle species. Its elongated, tapered head ends in a beak-like mouth (from which its common name is derived), and its beak is more sharply pronounced and hooked than others. The hawksbill's arms have two visible claws on each flipper. One of the hawksbill's more easily distinguished characteristics is the pattern of thick scutes that make up its carapace. While its carapace has five central scutes and four pairs of lateral scutes like several members of its family, ''E. imbricatas posterior scutes overlap in such a way as to give the rear margin of its carapace a serrated look, similar to the edge of a saw or a steak knife. The turtle's carapace has been known to reach almost in length. The hawksbill appears to frequently employ its sturdy shell to insert its body into tight spaces in reefs. Hawksbill sea turtles' sand tracks are asymmetrical, because they crawl on land with an alternating gait. By contrast, the green sea turtle and the leatherback turtle crawl rather symmetrically. Due to its consumption of venomous cnidarians, hawksbill sea turtle flesh can become toxic.〔(【引用サイトリンク】url=http://www.aucklandzoo.co.nz/sss/sss_003/SSS3.hawksbill_turtle2.htm )〕 The hawksbill sea turtle has been shown to be biofluorescent and is the first reptile recorded with this characteristic.〔(【引用サイトリンク】title=Exclusive Video: First "Glowing" Sea Turtle Found )〕 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「Hawksbill sea turtle」の詳細全文を読む スポンサード リンク
|