Giant turtles built for comfort, not speed.Giant turtles built for comfort, not speed It's not easy to measure the metabolism of a 1,000-pound turtle. But three researchers who took pains to do so have characterized a mechanism that allows these large reptiles, traditionally considered "cold-blooded," to stay warm in chilly environs. Their findings support the controversial proposition that cold-blooded dinosaurs could have lived comfortably in the Cretaceous Arctic, about 100 million years ago. Frank V. Paladino of Purdue University Purdue University (pərdy  `, -d`), main campus at West Lafayette, Ind. at Fort Wayne, Ind., working with Michael P. O'Connor Michael Patrick O’Connor (September 29, 1831 - April 26, 1881) was a U.S. Representative from South Carolina.Born in Beaufort, South Carolina, O’Connor attended the public schools and was graduated from St. John's College, Fordham, New York, in 1850. and James R. Spotila of Drexel University in Philadelphia, studied the leatherback leatherback, marine turtle, Dermochelys coriacea, found in tropical, subtropical, and temperate waters around the world. The largest of all turtles, it may reach a length of 7 1-2 ft (230 cm) and weigh 1200 lb (540 kg). turtle, Dermochelys coriacea, one of today's largest reptiles. Biologists classify turtles as ectothermic ectothermic or ec·to·ther·mal or ec·to·ther·mous adj. Of or relating to an organism that regulates its body temperature largely by exchanging heat with its surrounding environment. , or unable to adjust their body temperatures significantly using metabolic reactions. But somehow, leatherbacks range from the tropics tropics, also called tropical zone or torrid zone, all the land and water of the earth situated between the Tropic of Cancer at lat. 23 1-2°N and the Tropic of Capricorn at lat. 23 1-2°S. to the Arctic and can maintain internal temperatures of 25 [degrees]C in 7[degrees]C seawater seawater Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. . The researchers put respirators over the snouts of six leatherbacks, then suspended the animals in tripod-supported hammocks for a few hours before measuring oxygen consumption rates. They also measured these rates in active, nesting leatherbacks and used mathematical models to predict heat-exchange rates through turtle tissues and blood. The bottom line, they report in the April 26 NATURE, is that although leatherbacks feature metabolic rates far lower than those in mammals, their insulating bulk lets them retain heat efficiently in cold environs. (In warm climes, they note, leatherbacks apparently enhance heat loss by increasing blood flow to their extremities.) The researchers suggest a new term for large reptiles' use of body mass to stay warm in the cold: gigantothermy. Fossils verify that dinosaurs spent time in the Arctic, but scientists remain divided over whether these huge reptiles simply migrated through the region -- which was cold in the winters but not permanently frozen -- or lived there year-round. Paladino says gigantothermy could have allowed dinosaurs to survive the chilly climate even without the high metabolic rates or hyperactive hy·per·ac·tive adj. 1. Highly or excessively active, as a gland. 2. Having behavior characterized by constant overactivity. 3. Afflicted with attention deficit disorder. behaviors that others have proposed. |
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