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Keehi jellyfish invaders
are out partying

For a few weeks now, paddlers in Keehi Lagoon have been stung by something in the water. Hawaii ocean-goers usually take a sting or two in stride, but this is different. These mysterious stings were so numerous, itchy and painful, organizers stopped the races there.

Because I co-authored a medical book with Craig Thomas called "All Stings Considered," we weren't surprised when reporters called us about this. But since we didn't know what caused the stings, we weren't much help.

Three days ago, though, local biologists identified the culprits: transparent little creatures, barely visible to the naked eye. They're calling them hydromedusae.

"Is that a jellyfish?" a reporter asked. Good question. Jellyfish biology is a language all its own, and few of us are fluent in it.

The names alone are enough to keep my head spinning. Most of us know a jellyfish when we see one: It looks like an upside-down bowl of jelly fringed with tentacles. But since jellyfish aren't fish, most biologists prefer the term medusa.

That Medusa is a Gorgon monster of Greek mythology who had snakes for hair and turned those who looked at her into stone doesn't matter. Medusa is the name researchers use for a you-know-what.

The "hydro" part of hydromedusa comes from a group of stinging creatures called hydroids, which grow on rocks, seaweeds, piers and just about anything else that holds still. Hydroids look like pretty white plants, but don't be fooled. These guys would be right at home in the Little Shop of Horrors.

A hydroid colony starts as one hollow stem that attaches to an object in a plankton-rich area. At the top of the stem is a mouth surrounded by tentacles. These lovely little "flowers" sting tiny, passing animals to death. The hydroid then swallows them whole.

A hydroid grows into a colony by budding. Outpouchings form along its stem to eventually become more stems, also with venomous mouths at the ends.

Besides those tentacles ambushing passing plankton, they are also part of the defense team. Touch a hydroid and you won't forget it.

But keeping your hands off hydroids doesn't mean you're safe. Some of a hydroid's buds turn into male and female medusae. These stinging rascals break off from their parents and swim away to release either sperm or eggs.

Fertilized eggs eventually settle down to become a new hydroid stem, starting the cycle all over again.

Hydromedusae, therefore, are tiny jellyfish out partying. Why they're so rowdy right now is a question for the Gorgon biologists.

In our book, Craig and I did consider all stings, including those from hydroids. If they make you miserable, try over-the-counter hydrocortisone ointment and oral antihistamines. Forget vinegar, meat tenderizer alcohol and urine. They don't work and might worsen the injury.

Heat, including sunburn, usually makes hydroid irritation worse, but ice packs might relieve pain.

See a doctor for allergy symptoms or generalized illness.