The comb jelly Mnemiopsis leidyi (pictured) is a highly effective predator, even though it does not actively pursue or look for its prey. Sean Colin at Roger Williams University in Bristol, Rhode Island, and his colleagues report that the animal captures its prey by producing a subtle current with its cilia — tiny beating hair-like structures. This current moves a large volume of water past its feeding apparatus.
By measuring fluid flow around jellies in the laboratory, the team showed that the current becomes turbulent enough to be detectable by typical prey species, such as microplankton, only in the capture zone near the creature's mouth. By then, it is normally too late for prey to escape.
Such 'stealth predation' partly explains the animal's success as an invasive species, say the authors.
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Zoology: Killer jelly hunts by stealth. Nature 467, 502 (2010). https://doi.org/10.1038/467502c