National Geographic : 2011 Jul
NOW PHOTO TOP : SYLVAIN PINCEBOURDE. ART: STEFAN FICHTEL Stars in the Sun An exposed ochre sea star may appear to bask in the sun, but air that's warmer than 73°F can harm---and, at 95°F, kill---this icon of the North Pacific coast. How does it keep its cool? By taking the temperature, then using its five-armed, balloon-like anatomy. A team of biologists in Bodega Bay, California, say sea stars use their time during low tide to assess the air. When waves roll in and submerge them, they fill cavities in their arms with frigid water, taking in more or less, based on the per- ceived air temperature. During low tide, those arms act like cold packs in a lunch bag, slowing heating. Yet these animals are also susceptible to changes in water temperature. Much like trying to chill a sandwich with cold packs left out overnight, the sea star's cooling system will fail if sea tem- peratures rise. Because it plays an outsize role in its ecosystem, the consequences could be worse than a spoiled lunch. ---Juli Berwald SNAP, CRACKLE, POP For such a modest creature, the two-inch-long snapping shrimp creates quite a racket. Also known as the pistol shrimp, the crustacean possesses an outsize claw that it cocks open and snaps shut at lightning speed. This motion generates tiny bubbles that implode, sending a shock wave at small crabs, worms, and other unlucky targets. The little blasts stun prey and, when emanating from colonies up to 300 shrimps strong, produce a collective crackle loud enough to interfere with sonar transmissions. Strength in numbers, indeed. ---Catherine Zuckerman An infrared photo shows that arms lled with cold water keep ochre sea stars cool, even in the sun.