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A couple of weeks ago, Star-Bulletin columnist Charley Memminger wrote a funny story about my new medical book, Pests of Paradise (Honolulu Lite, Aug. 2).

It seems the section about cockroaches crawling into people's ears was keeping him awake at night.

Well, a cockroach in the ear is trivial compared to the mischief a creepy little catfish called candiru can cause. This Amazonian fish swims into the urethras of submerged men and women who urinate in the water.

The fish anchors itself inside the body with serrated gill spines, then drinks blood oozing from the person's injured tissue. Often, the only way to get the fish out of a man's penis is to amputate.

Or so the stories go.

This whole thing sounded a little fishy to me, and sure enough, the articles I found about this fish attacking humans were either suspiciously old (1930s and '40s) or so poorly written that the author's credibility was questionable.

There is no doubt, however, that the fish exists. This skinny, 1- to 2-inch-long catfish is formally known as Vandellia cirrhosa and lives in the rivers of tropical South America. There it attaches itself inside the blood-rich gills of fish and takes a blood meal. Afterward, the catfish swims to the bottom of the river to digest.

For ages, native Amazonians have told spooky stories about this tiny vampire fish, called candiru in Brazil and carnero in Spanish-speaking countries. Adults of the region warn children that they must never urinate in the water because these sneaky fish sense urine trails and will swim inside the kids.

This frightening story would stop anyone from urinating in the water, which may be the whole point. One catfish researcher believes that the root of these tales is the need to keep village streams, the only source of drinking water, unpolluted.

His investigations found no proof that this fish has ever entered a human being.

But that doesn't stop the stories. In the film "Medicine Man," Sean Connery warns a visiting scientist bathing in the river not to urinate because of the dreaded candiru. The fish also emerges in an account of a recent British expedition to the Amazon.

Leaders had their workers wear "cricket box" type shields while swimming or wading to keep the candiru out of their urethras.

Probably the strangest place the little catfish has appeared is in an ad for a preparation course for the Medical College Admission Test (MCAT), an exam required for entrance to American medical schools. The flyer said, "The candiru is a tiny parasitic fish that swims into one's urinary tract and extends its spines into the walls of the urethra, causing excruciating pain. We tell you this so that if you don't get into medical school, you will know that there are others suffering more than you."

As you might expect, the importation of any member of this catfish family (sometimes called pencil catfish) is strictly prohibited in the U.S.

The marine equivalent of the candiru is the pearl fish. This little tropical fish gets its name from slipping into the partially open shells of living oysters for shelter. One kind of pearl fish prefers hiding in the respiratory trees of sea cucumbers. Like its oyster shell cousin, this fish leaves the cucumber at night to eat, then returns, forcing its way into the sea cucumber via its anus.

I have never heard of pearl fish bothering humans, but it's easy to see how unnerving stories about them might get started. Don't believe them.

Sweet dreams, Charley.