Ochre starfish have a cooling system

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Ochre starfish have a cooling system

October 13, 2011 - 01:15
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Starfish suck up seawater to cool down.

Ochre Starfish wait out the low tide on a rocky shore off Vancouver Island

Pisaster ochraceous can be found on wave-washed rocky shores, from above the low-tide zone to 90 m in depth. Because they can live in shallow water they need to survive in these living conditions, including strong surges, big temperature changes, dilution by rainfall, and dessication. Pisaster ochraceous is very resistant to dessication and it can tolerate a loss of thirty-percent of its body weight in body fluids.

The Ochre starfish Pisaster ochraceous is most commonly found in the Northeastern Pacific, where, at low tide, it can often be seen in tidal pools and sitting tucked away in rock crevices.

During low tide, it is exposed to the air and cannot move until it is submerged again at high tide. If it is also exposed to the sun, it can suffer heat stress.

Now, scientists have discovered that this humble starfish has developed a remarkable strategy to avoid overheating; it pumps itself up with cold seawater to lower its body temperature when exposed to the sun at low tide.

Writing in The American Naturalist, Dr Pincebourde and colleagues at the University of California, Davis and Bodega Marine Laboratory, Bodega Bay, California, the scientists expressed their surprise by the amount of water the starfish were able to store in a few days.

"It's as if we decided to suck up more than 15 pounds of cold water in the morning to prepare ourselves to the high temperature we will get at noon," Dr Pincebourde explains to BBC Earth News.

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