Kids Page - Jellyfish

December, 2015

 Did you know that jellyfish move by squirting water out of their mouth? Did you know they use the same mouth (their anus) to get rid of waste? Jellyfish aren’t really fish at all. Fish are vertebrates (have a backbone), while jellyfish are invertebrates (do not have a backbone). 

Jellyfish are a type of plankton.  Sometimes they’re called jellys. Jellyfish are among some of the oldest living organisms on the planet, having been around for about 700 million years.  They can be found living in every ocean from the very deep waters to the surface.  You can find them washed up at the beach or in some freshwater lakes and ponds all around the world.

There are over 1,000 species of jellyfish.  The most common types are: box, comb, and medusa, with an umbrella-like body and tentacles flowing underneath the umbrella-like body.  They can have tentacles up to 100 feet long!  Their bodies are made up of 98% water and have no brain or heart.

Jellyfish feed on small invertebrates, fish, crabs, mollusks, diatoms, fish eggs, and some are even vegetarians.  The vegetarian jellys float on their backs and grow algae on their bellies and that’s what they eat. 

When new jellyfish are born they come out several at a time and become very small polyps.  They stick to rocks and look like very small sea anemones.  They remain polyps for many months, up to years, and then they become ephyrae  (small jellyfish).  These little ephyrae look like little jellyfish umbrellas stacked on top of each other, like a skyscraper. Each adult jellyfish has a 3-6 month lifespan. 

Many things eat jellyfish, such as sea turtles and even humans.  The jellyfish’s main defenses are called nematocysts.  This is what’s responsible for the jellyfish sting you may have heard about. It feels like a burn, and can cause blisters.  They are able to sting after they’re dead.  If you are stung, vinegar, coke, urine, or just water splashed on the “bite” can help.  Don’t rub the area because that could make more of the nematocysts to erupt. 

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