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Three Curious Facts About Jellyfish

by AMNH on

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Jellies may seem like some of the strangest and most alien-looking animals on the planet. Here are just three ways in which species in these two groups—cnidarians and ctenophores—set themselves apart.


Five jellyfish shaped like mushrooms with dangling tentacles float underwater.
The Lagoon Jelly (Mastigias papua) lives in shallow waters and takes food in through openings in its oral-arms.
Image courtesy of Wikimedia Commons

First, they move in fascinating, but distinct, ways. True jellyfish (cnidarians) propel themselves by “pulsing”—pulling and pushing water in and out of their bodies. Comb jellies (ctenophores) paddle through the water with tiny oar-like cilia. 

Jellies of both types are also extremely resilient. Some species can regenerate, or regrow, lost body parts. A rare few are even able to cheat death by “aging backwards.” These jellies can transform back into tiny polyps (the first stage of the jelly life cycle), and then grow into identical copies of the original adult.


immortal jellyfish (Turritopsis dohrnii) polyp
In response to physical damage or starvation immortal jellyfish take a leap back in their development, transforming back into a polyp. 
Takashi Murai/The New York Times Syndicate/Redux

Finally, jellies can glow! Many species, especially in the deep sea, are bioluminescent, producing their own light through a chemical reaction in their bodies. Other jellies are biofluorescent, meaning they absorb one light of color and emit it as another. This is how comb jellies generate glistening rainbow colors when they swim.


Jellyfish has the appearance of strands of glowing light coming together to form a bulbous shape.
Bathocyroe fosteri, a species of bioluminescent comb jelly common in the Mid-Atlantic.
Courtesy of M. Youngbluth/Wikimedia Commons

To learn more about jellies—and experience life in their underwater world—visit The Jelly Dome through June 30 in the Milstein Hall of Ocean Life.

*Jelly Dome hours are subject to change, please visit the site for details and updates.