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April 11, 2012

Meet the Hairy Jellies

Hairy jelliesThe hairy jelly, with its clear, squarish bell that surrounds white filamentous reproductive organs, looks a little like a light bulb. But the seasonal species in the Jellies special exhibit gets its common name from the thick fringe of fine, transparent tentacles that hang from the edge of the bell.

Sometimes a hairy will swim along the bottom of the habitat, dragging its tentacles to sweep up planktonic food from the bottom into its tubelike mouth, which hangs even with or below the bottom of the bell. Look closely and you’ll see tiny red dots on the base of the tentacles, along the bell margin. These are eyespots—not eyes, but clusters of photo-sensitive cells. Not all jelly species have them. 

Maureen Koneval, one of the special exhibits aquarists, says that when the light level decreases, the hairy jellies’ pulsing rate increases. Being able to distinguish between light—open sea—and dark—the shadow of a predator—could trigger a basic flight response in these jellies. Maureen notes that when a hairy jelly is bumped, it retracts it tentacles and pulses away in the opposite direction. This illustrates how jellies—brainless though they are—have used the most basic senses to stay ahead of predators for 500 million years.

Posted by Karen Furnweger, web editor

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