Marco Faasse/World Register of Marine Species
Comb jellies may look like little more than filmy ghosts twinkling in the sea. Yet their immune systems can tell whether the jellies have encountered certain bacteria before.
Biologists once thought only vertebrates could recognize a familiar foe and tailor an immune response to it, says Sören Bolte of the University of Kiel in Germany. But insects and crustaceans turn out to have their own ways of accomplishing the same memorylike task.
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