With a "cheep-cheep cheeep!" a water ouzel flashes past Peter Hovingh, who is standing, bent over, up to his knees in a swift, clear stream. He is pulling up rocks from the bottom of the stream and inspecting them.

The swift current burbles between browned grasses, not yet revived by spring growth. Walking with the current, thongs on his feet, Hovingh fishes up a rock the size of two fists. He stops, turns it over and finds one on it."These are the kind that eat its prey whole," he said, holding out the glistening rock. Several dark things are moving across the rock, stretching, pulling themselves into lines about 3 inches long.

They are fine examples of Erpobdella dubia, one of Utah's largest leech species.

"See, this guy will live on snails, other worms, other leeches, crustaceans," he said. Some in the Colorado River eat small fish. In certain Utah springs, you can find "big ones, around 24 inches long when they're stretched out."

Hovingh is a biologist who works at the Department of Veterans Affairs in Salt Lake City. Some of his leech research has medical applications: "In their little heads they have quite a pharmaceutical company. Depending on their species, there's at least three different anticoagulants coming out of the leech."

He is also interested in discovering secrets of the hyaluronidase produced by leeches. This is a material that breaks down the structure of hyaluron acid. "It may break down tissue and make blood flow fast," he added.

"What we're now looking at is the specificity of the enzyme." Hovingh and fellow scientists would like to know whether there are other molecules besides hyaluron acid that it dissolves. If so, they may find previously unimagined uses for it.

But today he isn't looking for cures. Wearing thongs and a floppy hat, he is splashing through streams near Kimball Junction to assist with purely scientific studies. All the leeches he collects here will be pickled and mailed to biologist Boris Sket of the University of Ljubljana, Solvenia, who is making genetic studies of leeches from around the world.

Hovingh became interested in leeches in the 1980s when he was in the Uinta Mountains studying salamander distribution. "In some of these ponds the leeches were very abundant," he said. "So, in line with the salamander studies, I noticed these great big leeches that ate other critters whole."

In a strange way, he muses, they can be considered as living at the top of a food chain, sort of an invertebrate cougar. They deserve investigation, Hovingh says, but in this country they aren't the focus of much natural history research.

"There's too little attention paid to all invertebrates . . . All the focus in wildlife management is vertebrate," he said. In fact, only a few game animals get most of the biological work: deer, elk, trout. Other vertebrates like the amphibians that Hovingh loves are ignored.

And where does it leave lower forms like muscles, insects, crabs and leeches? "Invertebrates consist of over 99 percent of animal life - certainly they get a lot less than 1 percent of the attention," he said.

If you get beyond basic squeamishness, leeches are interesting creatures. "Some of them are pretty colorful. Some are kind of green. Some are bluish," Hovingh added.

He turns up a whitish lump attached to the underside of a rock. It is a leech cocoon, where eggs are developing. "There could be up to a dozen leeches in each cocoon," he said.

Once he was searching in a stream when he met up with two biologists working for a federal agency. They asked him what he was doing out in the wilds and he replied he was looking for leeches. "I thought all the leeches were in Washington," one of the feds cracked.

The story leads him to reflect on aquatic biologists. Most of them deal strictly in fish. Everything else in the stream is just habitat, in their view.

Suddenly, Hovingh finds a tiny, gray leech hanging onto a rock - an example of Helobdella stagnalis.

"These stick-in-the-straw leeches are probably more primitive," he said.

Genetically, they may be the most interesting leeches. They are found in Africa, Asia, Europe and the Americas - populations separated from each other by thousands of miles of salt water. "The question is, has this leech species been around for 200 million years, and they are found in these continents because of continental drift?" he asked.

Are they truly the same species? Are there subspecies that have developed because of the millennia that populations have spent away from each other? Are they entirely different species that happen to look and act alike?

The leeches Hovingh sends to Slovenia may help answer those questions. Genetic typing can show precisely how closely related a leech from Europe is to one from Utah.

Perhaps they are the same species and this type of leech has not changed for many millions of years. Their habitat is so filled with prey, the fresh water they need is so pervasive, "that there has been no selective pressure for them to change."

They are like another predator, the shark. "If you're successful, you don't have to change," he said.

"Here's a leech collection," Hovingh said, holding out a rock with three fat, dark leeches and several smaller, gray ones. He peels them off, dropping them into collection vials.

As part of his respect for the natural environment, he tries to replace the rocks in the same spots in the stream bed where he found them. But occasionally, when he has made a surprising find, he may not put one back exactly where it was.

"Sometimes you get so excited you forget where they were," he explained.

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ADDITIONAL INFORMATION

Facts

Leeches have been used for medical purposes since the days of the ancient Greeks. Medical supply houses today regularly provide leeches for hospitals, which use them for such needs as drawing off blood when fingers are swelling because of serious injuries.

Leeches belong to the annelid family (segmented worms) of invertebrates. Annelids have thrived since the Cambrian era 530 million years ago.

They are armed with suckers at both ends. They stretch and contract. While feasting, a leech may expand two to three ties normal size - enough food to last a couple of months.

External features of a leech

Posterior sucker, segment, dorsal surface, prostomium.

Leeches breathe through their skin.

Every leech has 34 body segments regardless of whether it's minute or the variety that reaches 24 inches long.