Scientists have long thought that many of the tiny marine crustaceans called copepods find their supper by colliding with it. Now new research shows the truth is less painful. Scientists unleashed Metridia longa, a copepod of the northern seas, into tanks of algae and found that an algal cell didn't have to bump into a copepod to be detected. Instead, algae that merely floated close to a copepod's antennae set off an "attack response," in which the copepod creates suction to draw in its prey, the team reports online today in Biology Letters. Researchers think the crustacean is responding to either chemical signals or the touch of an algal cell on its antennae. Either way, this detection method, which has never been described before, could help explain how copepods survive in the ocean, where food is so scarce that it's inefficient to rely for meals on things that go bump in the night.
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