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Jellyfish: millions of years of stinging success


July 29, 1996
Web posted at: 9:20 p.m. EDT

From Correspondent Ann Kellan

BALTIMORE, Maryland (CNN) -- If you enjoy a dip in the ocean this time of year, beware: it's jellyfish season.

But even though some species' stings can be deadly to humans, they are an important source of food for sea life, and quite a spectacle behind glass. The National Aquarium in Baltimore, Maryland, is one place to see them in a friendlier setting.

"Jellyfish have been around for millions of years. They're very well adapted to surviving in the oceans," said Mark Donovan with the National Aquarium in Baltimore. "And, what makes them so neat ... they're kind of something that the public doesn't really understand."

movie.icon(519K QuickTime movie of jellyfish)

There are 2,000 species of jellyfish and many have unusual names, like the upside down jellies, the moon jellyfish, the tiny umbrellas, and the West coast and East coast nettles.

Seven different jellyfish species grace the aquarium's tanks, from the tiny elegant jellyfish, as they're called, to the lion's mane, which packs the most powerful sting of the bunch.


"They sting in order to capture their food," Donovan said. "It's just a coincidence that man kind of goes into their area in the oceans and gets stung."

The sting comes from tiny weapons on the jellyfish's tentacles.

"They fire all these little nematocysts, which are millions and millions of little harpoons, to kind of grab the food and pull it into them," Donovan added.

The jellyfish have what are called oral arms that move the food to their mouths. The jellies in the exhibit get to feast on specially-prepared brine shrimp.

Looks can be deceiving

The aquarium's exhibit is not quite as simple as it seems, but then neither are the jellyfish. They live in special tanks, that are designed to simulate the moving ocean, which keeps the jellies afloat. Without moving water, jellyfish will sink to the bottom and die.

Another challenge to keeping them alive is keeping bubbles out of the tanks. Bubbles can literally eat their stomachs out, or collect on the jellyfish making them so buoyant they also die.

Moving them from tank-to-tank is also tricky, because these primitive creatures are 95 percent water.

Aquarium visitors also learn some interesting facts about nature. For example, jellyfish are not even fish, they are spineless invertebrates. And Man o' Wars (such as the Portuguese) are not quite jellyfish. However, they are a colony of stinging animals that are members of the same family as jellyfish.

The jellyfish may be headless, heartless creatures, but they've earned the respect of those who visit the aquarium's exhibit. After all, they've managed to survive 650 million years on this planet.


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