Study: Sea stars bulk up to beat the heat

TOURS, France, Nov. 19 (UPI) -- French and U.S. scientists say they've found a species of sea star remains cool by retaining cold sea water as a buffer against damaging high temperatures.

The researchers from the University of South Carolina and Francois Rabelais University in Tours, France, say the strategy has never been seen in the animal kingdom.

"Sea stars were assumed to be at the mercy of the sun during low tide," said Sylvain Pincebourde, the study's lead author from Rabelais University. "This work shows some sea stars have an unexpected back-up strategy."

Sea stars need to endure rapid changes in temperature, the scientists said, since during high tide they are fully submerged in cool sea water. But when tides recede, the stars are often left on rocky shorelines, baking in the sun. However, scientists have been uncertain how the stars survived the heat.

In their experiment, the scientists found stars exposed to higher temperatures at low tide had higher body mass after high tide that followed. The increased mass came from the stars soaking up water.

"This reservoir of cool water keeps the sea star from overheating when the tide recedes again the next day, a process called 'thermal inertia,'" Pincebourde said.

The study that included co-author Brian Helmuth, an associate professor at the University of South Carolina, appears in the journal The American Naturalist.