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sea turtle

sea turtle, name for several species of large marine turtles found in tropical and subtropical oceans. These turtles are modified for life in the ocean by having flipperlike forelimbs without toes and lightweight shells. Their heads are too large to be withdrawn into the shell. They spend most of their lives in the water, but come ashore to lay their eggs. Nearly all species have a circumglobal distribution although there are differences between the Atlantic and the Pacific populations. Most sea turtles are found in North American waters as far N as the U.S. S Atlantic coast and Baja California.

All sea turtle species are declining in numbers, owing in large part to the destruction of the eggs, which are widely used as food in tropical regions. Sea turtle meat is also eaten, and there is a market for turtle oil, hide, and shell. In a few places, such as Sarawak, harvesting of eggs is regulated by law to insure propagation of the species. The size of sea turtles has also decreased, owing to the hunting of large specimens.

The green turtle, Chelonia mydas, with greenish to brownish skin and shell, formerly reached weights of 1,000 lb (450 kg); the largest now found are about 4 ft (120 cm) long and weigh about 500 lb (225 kg). The green turtle feeds chiefly on marine vegetation and is most abundant in shallow water. The loggerhead, Caretta caretta, is a large-headed brown to reddish turtle. Chiefly carnivorous, it ranges from open oceans to coastal salt marshes and stream mouths. Like the green turtle it sometimes comes ashore in uninhabited places to bask.

The hawksbill, or tortoiseshell turtle, Eretmochelys imbricata, may reach 30 in. (75 cm) in length and weigh 100 lbs (45 kg). The horny plates of its shell are translucent and have a variegated color pattern, chiefly brown and yellow. These plates have long been valued for the making of ornamental objects. Although tortoiseshell has to a large extent been replaced in many applications by plastic, a renewed demand for the genuine material poses a serious threat to the hawksbill.

The ridleys, the smallest sea turtles, inhabit shallow offshore waters. The 2-ft (60-cm) long, gray Kemp's, or Atlantic, ridley, Lepidochelys kempii, breeds only in the Gulf of Mexico, although the young are often carried by the Gulf Stream to the Carribean Sea and Europe. The slightly larger, greenish olive, or Pacific, ridley (L. olivacea), also known as the oliveback, is found in the Indian and Pacific oceans. The leatherback is the largest of all turtles; it belongs to a separate family from the other sea turtles.

All sea turtles other than the leatherback are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Chelonia, family Chelonidae; the leatherback belongs to the family Dermochelidae.

Bibliography

See J. R. Spotila, Saving Sea Turtles (2011).

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loggerhead

1. a large-headed turtle, Caretta caretta, occurring in most seas: family Chelonidae
2. loggerhead shrike a North American shrike, Lanius ludovicianus, having a grey head and body, black-and-white wings and tail, and black facial stripe
3. a tool consisting of a large metal sphere attached to a long handle, used for warming liquids, melting tar, etc.
4. a strong round upright post in a whaleboat for belaying the line of a harpoon
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Tiger sharks are considered to be (http://www.iucnredlist.org/details/39378/0) at lower risk than loggerheads. They, too, have a wide range and face threats from fishing bycatch and intentional harvesting.
A total of 96 critically endangered juvenile hawksbills, one juvenile loggerhead, two juvenile greens and one large adult loggerhead were released.
According to Dana Al Sarhani, a board member of ESO, they are conducting various activities to protect the Loggerheads on the Masirah Island.
The study by the University of North Carolina focused on loggerhead sea turtles, which cover thousands of miles periodically, guided by the Earth's magnetic field.
Savannah, Georgia - Sea turtle experts along the southeastern US coast say new nesting numbers reinforce their belief that loggerhead sea turtles are making a comeback after 37 years of protection as a threatened species under the federal Endangered Species Act.
Loggerheads are the most common type of sea turtle in the southeastern United States.
HATAY (CyHAN)- Mother loggerhead turtles, which are endangered, have started to lay their eggs in Turkish southern province of Hatay's Samanday- district on the coasts Mediterranean.
Instead of Paul (right), a loggerhead turtle called Big Head has been found and is sticking his neck out by tipping Brazil.
Due to lack of resources, we did not measure estradiol-17[beta] in samples from nesting females; however, estradiol was measured in several other studies on nesting sea turtles [8, 21-23], including nesting loggerheads [24], and data show that estradiol exhibits a nearly 10X lower concentration during nesting in relation to mating, with surges nearing 700 pg/mL after every nesting event [24].
Some juvenile loggerheads along Florida's east coast undergo seasonal migrations northward in warmer months and migrate south when water temperatures decline in the fall (Lutcavage and Musick, 1985; Carr, 1987; Musick and Limpus, 1997; TEWG, 2009).
Hana Al Suwaidi, head of Sharjah's Environment and Protected Areas Authority, said the team, along with the World Wildlife Fund, had found about 385 turtle nests and believes there are three rare breeds of turtle on the island--the hawksbill, loggerheads and green turtles.