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Sharks Found to Have Heat-generating Muscles
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Sharks Found to Have Heat-generating Muscles

July 26, 2010
Lamnid sharks, a group of sharks that includes the salmon, great white and mako, maintain an elevated temperature (68-86 degrees Fahrenheit) in the red muscle concentrated in their mid-region near the backbone. This specialized anatomy allows the predators to swim fast and continuously, which in turn, allows heat to be retained in the core of the fish leading to local warm-bloodedness. In most other fish, the red muscle is located close to the skin, yielding a fully cold-blooded body and only short bursts of rapid, powerful swimming.

After catching specimens over seven-feet long and weighing more than 300 pounds, researchers measured temperatures throughout the sharks' bodies and tested the mechanical power of red muscle samples. The results of the National Science Foundation-supported study, published in the journal Nature, showed that at 50-degrees F, red muscle produced only 25-50 percent of the power it produced at 79-degrees F. The researchers concluded that red muscle temperatures below 68-degrees F could permanently impair muscle function.