There is a small, delicate, little creature that is common in Michigan lakes and streams, but rarely seen. It’s the freshwater jellyfish (Craspedacusta sowerbyi), and it’s this time of year that they are able to be seen in their jellyfish form. 

The freshwater jellyfish is considered to be an invasive species, but the Michigan Department of Natural Resources says, 

Don’t be concerned though. These jellyfish are not harmful to humans and are believed to have negligible adverse effects on the aquatic environment.

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So How Did These Tiny Jellyfish Arrive in Michigan? 

The MDNR believes that they are native to China and Asia. Many invasive species that roam the Michigan waters come from “bilgewater” from the freighters that travel the Great Lakes. The first documentation of freshwater jellyfish in Michigan occurred in 1933 from the Huron River in southeast Michigan. Today, they can be found in most Michigan lakes and streams and are most frequently spotted in lakes in the late summer and early fall. 

Can These Sting You, Like The Large Saltwater Jellyfish? 

According to the Mayo Clinic, large jellyfish are known for their powerful stings from the long tentacles, trailing from the jellyfish, which can inject venom from thousands of microscopic, barbed stingers. The sting causes instant pain and inflamed marks on the skin. 

The good news is that the small freshwater jellyfish is harmless. According to Tim Cwalinski, the DNR's northern Lake Huron manager,  

Though freshwater jellyfish do have stinging cells like the marine species, their tiny size means they lack the ability to sting, and so they're not harmful to people. 

A Tiny Freshwater Jellyfish. Have You Ever Spotted One?

A small freshwater jellyfish, found in some Michigan lakes and streams.
Greg Lashbrook,

Freshwater Jellyfish Sightings Trigger Calls To MDNR 

Even though this little invader, from lands beyond, is now common in Michigan waterways, rare sightings of these small invertebrates often trigger calls to local DNR offices. Cwalinski believes, 

We generally think our waterways are inhabited only by fish, aquatic plants, waterfowl, and various invertebrates. However, there is an entire other spectrum of life under the surface, such as plankton, bryozoans, and jellyfish. 

View This Short Freshwater Jellyfish Video From WOOD TV8

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