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Have you seen jellyfish?

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Jellyfish pulse through Northland lakes

AQUATIC CREATURES: Most Northland residents have never seen one, but higher water temperatures may be bringing them out of hiding.



A tiny creature rarely seen by most Northland residents is showing up in local lakes this year, probably because of high water temperatures and low water levels.

Freshwater jellyfish have been reported in a few area lakes in recent weeks, with samples taken from at least two.

While they have been around for years, most people have never seen one because the jellyfish spend most of their lives as underwater polyps that live on or near lake bottoms.

Only occasionally, and scientists aren't sure why, do they develop into dime- to quarter-sized jellyfish that can be seen floating and pulsing near the surface.

Most sightings are in August and September, experts say. The "blooms" last only a few days.

"It's an odd little critter that's in some of our lakes that we don't know a whole lot about," said Gary Montz, aquatic biologist for the Minnesota Department of Natural Resources division of ecological services. "They sometimes don't appear for years, then suddenly there's an explosion of them in a particular lake. It only lasts for a few days, though, so a lot of people have never seen one."

Chad Polecheck of Esko saw "thousands and thousands" of the jellyfish while fishing on Little Sturgeon Lake north of Hibbing in late July.

"We were fishing in a shallow bay for bluegills... and I joked with my wife that all the pollen in the water looked like jellyfish. Then I looked closer and they were jellyfish," said Polecheck, a former Minnesota conservation officer.

He scooped up a few in a glass bottle and was fascinated by their movement.

"They were a clear white, just beautiful," Polecheck said. "I'd never seen them before, never even heard of them."

Another report recently came from Dodo Lake near Duluth. Those jellyfish were on display last month at Fisherman's Corner bait shop outside Duluth.

It's still safe to go into the water, though. While freshwater jellyfish have tiny tentacles to sting and capture zooplankton, they are too small to sting people like their larger saltwater cousins can.

Montz said jellyfish -- Craspedacusta sowerbii -- have been in Minnesota lakes for decades. They are naturally occurring now, but they probably are an invasive species, possibly from Europe.

So far, however, there's no sign of any ecological disruption or damage from their presence.

"We have not been able to identify any long-term effect on lakes due to the jellies," said Dr. Terry Peard, professor of biology at Indiana University.

Peard said there could be more jellyfish now as northern lakes get warmer earlier in the year and stay warmer later. Northland lakes on average now have two weeks less ice cover than they did 50 years ago.

"We know in the laboratory that we can influence the production of the medusa buds (the jellyfish stage) from the polyps by adjusting the temperature and feeding rate," Peard said.

With the Northland experiencing its warmest summer in recorded history, and lowest water levels in decades on many lakes, warmer water probably reached the polyps attached to the bottom of lakes and helped spur more jellyfish "blooms." The jellyfish-stage critters then reproduced asexually, and tiny eggs attached to the bottom of the lake and became polyps, restarting the cycle.

Usually, when in the jellyfish form, the creatures are white or green and nearly gelatinous -- 99 percent of their bodies consist of water. The jellyfish lacks a head, has no skeleton and contains no organs for respiration or excretion.

Freshwater jellyfish are found throughout the world, but were first reported in 1880 in England. They were first reported in the U.S. in 1908, according to the University of Michigan's Museum of Zoology. They've been reported in 43 states.

A national freshwater jellyfish Web site lists several lakes in Minnesota as having recent jellyfish reports, including Arrowhead Lake in Cook County, Bowman Lake near Twig, Embarass Lake near Biwabik, Fourtown Lake in the Boundary Waters Canoe Area Wilderness, Hobson Lake near Hibbing, Hunter Lake near Duluth, Lake Jane near Lake Elmo, Leech Lake, Loon Lake near Ely, Sand Lake near Moose Lake and Wynne Lake near Biwabik.

They have been reported in more than 40 lakes in Wisconsin, including Augustine Lake near Glidden, Crystal Lake near Wascott and Viola Lake near Danbury.

Montz said people lucky enough to have seen a jellyfish this year shouldn't expect to see them again anytime soon.

"Even if you saw them this year, you may not see them next year or for many more years," he said. "It looks to be temperature-related. But we really don't know why it happens only in some lakes and only some years."

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Hmm. I thought the only jelly like fish in Minnesota was lutefisk. smirk.gif

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