IT DOESN'T itch, but it's sure got biologists and cottagers scratching their heads. We're talking the spiny water flea. Never heard of it? You will.

Although it's still too soon to tell, there's the possibility that this microscopic critter could turn out to be a nuisance exotic on the scale of the zebra mussel.

Norman Yan, a York biologist, has received a $25,000 grant to research the spread of the spiny water flea and its effect on large and small lakes. Yan's area of expertise is the effects of eco-stressors on Canadian Shield lakes.

The flea is one in a long line of more than 140 non-indigenous species ­ including the zebra mussel and the lamprey ­ now found in the Great Lakes and is among 50,000 non-indigenous species in North America. The flea's first confirmed sighting was in 1982 in Lake Ontario, and now the exotic has spread through all the Great Lakes, and since 1989, is rapidly invading Ontario's inland waters as well.

"Already sport fishermen report the flea has proved a nuisance because it wraps its tail around fishing lines ­ there are so many of them that it makes reeling up trolling lines impossible," says Yan. "We expect it may have an impact on small fish that feed on zooplankton. Anytime you add another level to the food chain it's a problem."