Ouch, That Stings!

Smaller jellyfish eat algae and other tiny plankton called zooplankton. Larger jellyfish eat crustaceans and bigger aquatic animals -- even other jellyfish. And, like we mentioned earlier, they don't seek out people to attack -- their nervous system is too simple to do that. Primarily, their sting is a way to capture prey, but it's also a defense mechanism, which is often how humans get stung. It's a matter of being in the wrong place at the wrong time. And that doesn't necessarily mean you're in the water. Jellies that have washed ashore can still sting, so be careful if you're investigating a beached specimen. Even a tentacle that has been separated from its jellyfish can sting.

Jellyfish (Leuckartiara sp), Weddell Sea, Antarctica © Ingo Arndt/Getty

Each jellyfish tentacle is covered with thousands of cells called cnidoblasts, which house nematocysts containing stinging threads. When a jellyfish encounters another object, pressure inside the nematocyst causes the threads to uncoil. The stinging cells spring out at the unwitting victim like tiny darts, firing venom into it. The venom is a neurotoxin designed to paralyze jellyfish prey. Although a jellyfish can kill a small aquatic animal, its sting is not usually fatal to humans (but it can be). A sting tends to cause pain, skin rashes, fever and muscle cramps. In more severe cases, blistering, welts, nausea and vomiting are possible. The degree of pain and reaction to a jellyfish sting can depend on the species -- larger jellyfish have larger cnidoblasts that can penetrate deeper into the skin, and some jellyfish have stronger venom than others do.

Sea Nettle (Chrysaora quinquecirrha) © Michael Durham/Getty

So, what do you do if you do get stung? First, remove any tentacles clinging to the skin. Don't wash the area with fresh water -- it could release more venom into your body. Instead, clean it with seawater, ammonia, vinegar or a baking soda and water solution. You can also apply meat tenderizer. You may have heard about people using rubbing alcohol or urine to cleanse the wound, but most evidence today suggests that isn't advisable. Many people believe urine and alcohol can do the same thing fresh water does, causing the nematocysts to continue firing. If the victim shows signs of an allergic reaction (shortness of breath, hives, wheezing), seek immediate medical attention. Sting-related fatalities can happen when the victim stops breathing because of an allergic reaction.

Sea Monster or Snack? The echizen kurage, a colossal creature (up to 6 feet wide and 450 pounds), certainly inspires the term sea monster. However, don't get carried away imagining man-eating beasts. It's true they've wreaked havoc, but not in a horror-movie-flesh-devouring-creature-from-the-deep kind of way. Three years ago, in the summer of 2005, marine biologists estimated that several million echizen kurage had converged on the waters around Japan. Japan's fishing industry took a huge hit as the giant jellies ripped through fishing nets, ruining the catch as they went. They even managed to disable a nuclear power plant temporarily after lodging in its cooling system. Today, these giant jellies continue to be a nuisance, but Japan's fishing industry is fighting back. Echizen kurage are one of several edible jellyfish -- so they're now on the catch-of-the-day list. Diners can enjoy it dried and salted, in tofu form or as a main ingredient in cookies and biscuits.