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It hasn't proven a threat, but the big questions are how it got to Bull Shoals Lake and why the tiny life form is snobbish about where it sets up residence, researchers said. "It appeared in two places simultaneously—here and in Texas," said Dr. John Havel, of the university's biology department.

He wonders how it got to those two locations at relatively the same time.

That was in 1990.

So far, the zooplankton have popped up in more than 100 reservoirs and lakes in North America and continues to spread.

Havel calls the zooplankton, Daphnia lumholtzi, an invasive life form that spreads quickly.

It is an exotic species native to subtropical lakes in East Africa, East Australia and India.

How and on what the aquatic life form hitches a ride to travel from one location to another is the big mystery that Havel would like to solve.

"The most likely culprit a shipment of Nile perch that were sent to Texas," Havel said. "They were introduced there as large sport fish."

Havel has been studying the Daphnia for almost nine years and research continues at the university's field station, located on Bull Shoals Lake. There, biology graduate student Tina Tamme is working on one aspect of the mystery.

Although the zooplankton thrive in Bull Shoals Lake, the ponds surrounding the lake remain uninhabited by them.

Tamme uses 20 small pools to simulate pond environments. She manipulates the environment with various sources of food and predators, such as salamander larvae, and hopes to discover what keeps the zooplankton from spreading to the neighboring ponds.

Recreational boats are high on the suspect list of possible carriers of the Daphnia.

"It lives in the live wells of bass boats," Havel said.

Although the zooplankton invasion of lakes and reservoirs hasn't posed a threat, there is evidence they may perform a positive role in the area ecology

"We know they are common in middle and late summer," Havel said. "The Daphnia eat microscopic plants, and fish eat the Daphnia."

So, why spend time and money researching a non-threatening little critter of a life form?

"It's proving that man is very influential in moving these things around," Havel said.

If Havel and his team can find out how the zooplankton are moved from continent to continent and from state to state, scientists can get a better understanding of how deadly scourges such as the West Nile virus disease are transported from place to place.

"There are a lot of similarities," Havel said.