Like humans, sea stars enjoy lounging on the shore during the hot summer months. But when they get too hot, they can't run for shade, so they have a back-up plan—fattening themselves with cold ocean water before the tide recedes, according to new research published in the journal The American Naturalist. This finding shows that sea stars, or ochre starfish, aren't as helpless as previously thought.
The sea stars are likely cued during low tide that it's a hot day, the researchers say, and that signals them to soak up more water during the next high tide. "It would be as if humans were able to look at a weather forecast, decide it was going to be hot tomorrow, and then in preparation suck up 15 or more pounds of water into our bodies," said study researcher Brian Helmuth [LiveScience]. Talk about staying hydrated.
The researchers first studied starfish in an aquarium using heat lamps to simulate a scorching summer day, an infrared camera to measure their internal temperatures, and a scale to weigh the sea stars and determine how much water they had absorbed. The researchers say the amount of water a starfish absorbs can decrease its body temperature by almost 4 degrees Celsius. But researcher
Sylvain Pincebourde
is concerned that this novel strategy may have limitations in a rapidly changing world.... As oceans warm together with air temperature the thermoregulatory mechanism used by the starfish will cease to work, he warns. "The colder the sea water, the more it is able to lower its body temperature. The efficiency of this thermoregulation strategy therefore might be annihilated by ocean warming" [BBC News].
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Yet another reason to get a handle on global carbon emissions.
Image: flickr / laszio-photo
