If you’ve swum in warm coastal waters off New England, chances are you’ve
come across translucent non-stinging comb jellies. The gorgeous gelatinous creatures – named for the comb-like structures they use for locomotion – are native here and elsewhere along the western
But they are dreaded invaders in the Black and Caspian seas and a growing
number of other places around the world that have seen a drastic and
harmful shift in ecosystems since the innocuous looking – but voracious -
jellies showed up. The creatures were likely introduced when ships emptied
their jelly-filled ballast water and, with few predators, underwent
The jellies devour zooplankton, tiny animals such as fish larvae and
crustaceans, which serve as one of the foundations of the ocean food web.
Scientists knew the jellies – sometimes so packed there can be several
hundred individuals per cubic yard - could ravage fish populations and
catches. But exactly how they were such effective and deadly predators has
been less clear.
Now, Sean Colin, a professor at Roger Williams University in Rhode Island <
– and a jelly expert – has figured out how the simple, slow-moving
creature, with no sophisticated sensory capabilities, is so effective at
catching so many tiny marine animals.
The answer is stealth predation, he explained in a recent paper in the
journal Proceedings of National Academy of Sciences. The comb-like
structures – called cilia – are continuously drawing in water at a steady
rate - so steady tiny animals can’t detect it.
“They sneak up on everyone,’’ said Colin. He says the method is so
effective the animals have catch rates comparable to far more sophisticated
predators like fish.
The comb jellies are not technically jellyfish, rather they are a related
species call ctenophores and go by other names, such as sea walnuts and sea
Photo caption: Lars Hansson
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