Atlantic Jellyfish

Jellyfish have drifted along on ocean currents for millions of years, even before dinosaurs lived on the Earth. They are abundant in cold and warm ocean water, in deep water, and along coastlines. Jellyfish have tiny stinging cells in their tentacles to stun or paralyze their prey before they eat them.

There are many types of jellyfish in the ocean. These jelly-like creatures pulse along on ocean currents. Inside their bell-shaped body is an opening that is its mouth. They eat and discard waste from this opening. As jellyfish squirt water from their mouths they are propelled forward. Tentacles hang down from the smooth bag-like body and sting their prey. 

Jellyfish stings can be painful to humans and sometimes very dangerous. But jellyfish don't purposely attack humans. Most stings occur when people accidentally touch a jellyfish, but if the sting is from a dangerous species, it can be deadly. The Australian box-like sea wasp is the most toxic to humans. 

Giant Jellyfish Invasion

Are aliens attacking the Sea of Japan? Not exactly. But these gigantic blobs are unwelcome visitors from another place. Called Nomura's jellyfish, the wiggly, pinkish giants can weigh up to 450 pounds (204 kilograms)—as heavy as a male lion—and they're swarming by the millions.

The supersize sea creatures—normally found off the coasts of China and North and South Korea—occasionally drift east into the Sea of Japan to feed on tiny organisms called plankton. But now one hundred times the usual number of jellyfish are invading Japanese waters. And local fishermen are feeling as if they are under siege.