GRAND RAPIDS, Mich. (WOOD) — Check out virtually any tourist shop along the lakeshore and you’ll find shirts, mugs and stickers that proudly claim Lake Michigan has no salt and no sharks. That is true, but did you know you can find wild jellyfish in the Mitten State?
It’s true, and Eastern Michigan University professor Cara Shillington is working to learn more about them.
Freshwater jellyfish — craspedacusta sowerbyi — were first found in Michigan in the 1930s. It is believed they originated in the Yangtze River in China and were brought stateside hiding in ornamental aquatic plants. They can also be carried from one body of water to another along with stocked fish, plants or by waterfowl. They have since been found in 45 states.
According to the Great Lakes Aquatic Nonindigenous Species Information System, the jellyfish were first found in Michigan in 1933 in the Huron River near Ann Arbor. Since then, they have been found in Lake Erie, Lake Huron, Lake St. Clair and dozens of inland lakes and streams.
That includes West Michigan as well. According to the U.S. Geological Survey, established populations of the tiny creature have been found in several West Michigan bodies of water and have been collected in dozens more.
According to the USGS, there are five lakes with established populations: Fenner Lake and Upper Scott Lake in Allegan County, Fine Lake in Barry County, Little Pine Island Lake in Kent County and Pettibone Lake in Newaygo County.
Shillington expects the jellyfish are much more common but simply haven’t been studied enough to be confirmed because they aren’t considered a hazard to the ecosystem.
“Freshwater jellyfish are not uncommon. The species that we have here is an introduced or nonnative species,” Shillington told News 8. “We prefer to call it nonnative rather than invasive because invasive typically implies that it is detrimental to the ecosystems. They’ve been here since the 1930s and from what we can see there is nothing that really indicates so far that they are particularly impactful.”
The tiny invertebrate organisms are translucent and grow to be about the size of a penny. The life cycle for a freshwater jellyfish is fairly short, advancing from an egg to a larva-like state and eventually, an adult called a medusa. Once they mature, the jellyfish live for a few weeks, release their eggs and die.
Freshwater jellyfish have four long tentacles and a series of short ones, anywhere from 50 to 500. The short ones are used to help them feed on zooplankton, while the long ones are used to stabilize them while swimming.
Unlike their saltwater brethren, you don’t have to worry about swimming alongside freshwater jellyfish.
“They do have nematocysts or stinging cells, but our skin is too thick for them to penetrate,” EMU graduate student Rachel Koski told News 8. “They normally use them for prey capture, and I don’t think they see us as prey.”
LEARNING MORE
This semester, Shillington led an elective course dedicated to learning more about freshwater jellyfish. Shillington and her class of 17 students took regular trips out to a lake in Washtenaw County to catch specimens and gather data on them.
“The idea was to figure out where we can find them and to, as a class, develop some ideas for projects as well as thinking about long-term monitoring,” Shillington said.” It was meant to be very broad with the idea that students can bring their own interests to it. And I really enjoy field work, so this was an opportunity to get students out into the field.”
The class took several snorkeling trips to the lake and captured between 20-30 “jellies.” Koski, who wants to focus her studies on marine invertebrates, called it a fun learning experience.
“I just love going out on the water, so every time we got to go out, I was super excited about it,” she said. “It was a good introduction for my thesis and seeing what I can do. And having 16 other people and their ideas of what we can do, not only for the class but also for my thesis.”
Abby Hoskins is an undergrad student at EMU and is majoring in biology. Shillington’s jellyfish course was her first class with an emphasis on fieldwork.
“It was a completely new experience. It was really amazing to get to go out into the lake. It was absolutely beautiful out there. And then to go get to swim with jellyfish and catch them,” Hoskins said.
As fun as it was, Hoskins said the searches weren’t easy.
“It was a learning curve. We tried using nets, but it didn’t really work. They are too fragile,” she told News 8. “The water is pretty murky at times. There is some clarity but they’re really difficult to see because they are so clear. … They look like bubbles. And we were snorkeling, so there were bubbles, everybody’s kicking around, people are wearing fins. So, you’re just like, ‘Is that a jelly or is that a bubble?’ Once you found one though, it’s like you knew what you were looking for so that made it a little bit (easier).”
Once the specimens were caught, it was time to monitor the jellyfish, collecting as many data points as possible.
“We were tracking where they were in the water column, where they were in the tank overall, tracking their pulse rates. Just collecting any data that we could,” Koski said.
Considering the success of the first run, Shillington plans to continue to offer the course to more students.
“It’s just so much fun. When the classroom is the lake, it was just so much fun,” Shillington said. “And while you are out there, it’s not just the jellies, it’s anything else that you see in the water, anything else outside of the water. As biologists and naturalists, it’s just fun to be out and have this as a class.”
She hopes to expand their research, as well, looking at more variables that impact the jellyfish and how the jellyfish impact the ecosystem.
“What happens with changes in climate? (What if we see) warmer winters? Colder winters? The length of the spring? Things along those lines and how that may influence these organisms. It tells us more about organisms in general and how they’re responding,” she said.
