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Freshwater jellyfish: don't worry, it won't sting you. Photo: OpenCage/Wikimedia Commons
Freshwater jellyfish have been spotted in Ohio ponds, alarming locals and surprising old timers. The local Newark Advocate quoted Frank Snelling, who has lived in the area for years, as saying, "I told him, 'You better drink a beer. There aren't jellyfish in Ohio.'"
Actually there are, because small freshwater jellyfish (Craspedacusta sowerbii) are native to Ohio as well as many other parts of the world. Marty Lundquist, a fisheries biologist with the Ohio Department of Natural Resources Wildlife Division, told the Advocate that his agency gets called about the small jellies every year.
Lundquist said the jellyfish like to live in ponds with good water quality, and that they usually hang out near the bottom. They prefer calm water and are also found in flooded quarries and lakes. They enter new habitats as polyps stuck to vegetation or birds, or transported in bait buckets.
The freshwater jellies do have stinging cells but they are so small that they usually don't hurt vertebrates (the whole animal is only about 1 inch (20–25 mm) across).
The jellies live off copepods and other zooplankton, which they paralyze with their ring of 400 slender tentacles. They pull their prey into their mouth, which hangs below the translucent bell. Freshwater jellyfish may have a whitish or greenish tinge.
These small animals have been reported in many countries around the world, from Thailand to India to Brazil, and in most U.S. states and Canadian provinces.
Like many jellyfish, this species has a complex lifecycle that includes a polyp phase, a larva phase, eggs, and the most familiar, the medusa (the one that looks like a jellyfish). When conditions get tough, they can wait it out in a dormant resting phase at the bottom.
So next time you take a dip in an old quarry or swimming hole, see if you can find any one-inch freshwater jellyfish. They won't sting you, and they're part of a healthy ecosystem.
Freshwater jellyfish prefer slow-moving, clean water and can be found all around the world. Photo: J. Michael Tracy, Wikimedia Commons
Brian Clark Howard covers the environment for National Geographic. He previously served as an editor for TheDailyGreen.com and E/The Environmental Magazine, and has written for TheAtlantic.com, FastCompany.com, PopularMechanics.com, Yahoo!, MSN, Miller-McCune and elsewhere. He is the co-author of six books, including Geothermal HVAC, Green Lighting, Build Your Own Small Wind Power System, and Rock Your Ugly Christmas Sweater.