Thresher sharks are capable of warming up their body tissues so they are a couple of degrees higher than the water they swim in, says research published today.
Diego Bernal and Chugey Sepulveda of the Department of Zoology at the Scripps Institution of Oceanography in California studied 24 Common threshers, Alopias vulpinnis, caught off the southern California coast to determine whether, like some other pelagic fish, they were capable of warming up their muscles above the temperature of the surrounding water.
The results of their study showed that, although there was some variability among individual sharks, Common threshers are definitely capable of significantly raising the temperature of their red aerobic muscle (RM) tissues.
On average, the fish raised the temperature of red aerobic muscle to 2.33C higher than the water temperature. The muscle tissues here were also up to 5-7C warmer than the tissues of the fast-twitch white muscle.
For more details see the paper: Bernal, D. and CA Sepulveda (2005) - Evidence for Temperature Elevation in the Aerobic Swimming Musculature of the Common Thresher Shark, Alopias vulpinus. Copeia: Vol. 2005, No. 1, pp. 146-151.