Jellyfish are probably some of the most unusual and mysterious creatures that you'll ever encounter. With their gelatinous bodies and dangling tentacles, they look more like something from a horror movie than a real animal. But if you can get past the weirdness -- and the fact that getting too close to one results in a nasty sting -- you'll discover that jellyfish are pretty fascinating. They've been around for more than 650 million years, and there are thousands of different species, with more species discovered all of the time.
In this article, we'll learn all about these mysterious animals and find out what to do if you do happen to get in the way of a stinging jellyfish tentacle.
A jellyfish's body generally comprises six basic parts:
The epidermis, which protects the inner organs
The gastrodermis, which is the inner layer
The mesoglea, or middle jelly, between the epidermis and gastrodermis
The gastrovascular cavity, which functions as a gullet, stomach, and intestine all in one
An orifice that functions as both the mouth and anus
Tentacles that line the edge of the body
An adult jellyfish is a medusa (plural: medusae), named after Medusa, the mythological creature with snakes for hair who could turn humans to stone with a glance. After the male releases its sperm through its orifice into the water, the sperm swim into the female's orifice and fertilize the eggs.
Several dozen jellyfish larvae can hatch at once. They eventually float out on the currents and look for a solid surface on which to attach, such as a rock. When they attach they become polyps -- hollow cylinders with a mouth and tentacles at the top. The polyps later bud into young jellyfish called ephyrae. After a few weeks, the jellyfish float away and grow into mature medusae. A medusa can live for about three to six months.
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