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US Fish And Wildlife Service Biologist Discovers New Parasites In Mississippi River

Newly Identified Species Highlight Diversity Of River Ecosystem

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Mississippi River in Prairie du Chien
A train travels over the Mississippi River in Prairie du Chien on Jan. 18, 2017. David Goldman/AP Photo

A biologist for the U.S. Fish and Wildlife Service in La Crosse has discovered two new species of parasites in the Mississippi River.

Eric Leis, fish biologist at the La Crosse Fish Health Center, said the parasites were discovered in the gills and liver of pirate perch from Lake Onalaska.

“They’re kind of an interesting fish because they live in really shallow water, and they’re not easy to capture,” Leis said. “There hadn’t really been any work done as far as the parasites that they might have and it was just a good opportunity to find a new species.”

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The two species, Hennegoides flockae and Henneguya marcquenskiae, are myxozoan parasites and are distantly related to jellyfish.

Leis said the new species belong to one of the most diverse groups of parasites in the world, many of which evolved millions of years ago.

“A parasite doesn’t want to harm the host necessarily, it just wants to reproduce and complete its lifecycle,” Leis said. “The problem with parasites occur when it’s invasive and the host isn’t used to seeing them around. But in this case, it’s probably a balanced coevolution that’s occurred.”

Leis named the new species after one of his former science teachers, Susan Flock from Sacred Heart School in Cashton, and Susan Marcquenski, retired fish health specialist for the Wisconsin Department of Natural Resources.

He said both people had important impacts on his career.

“It’s just an interesting way to say thanks, and I’m really glad that I can do that,” Leis said.

Marcquenski said she was honored to learn of Leis’ decision, especially because she started her career in parasitology.

“Parasites are so clever because they not only can live in one host, they can modify the structure of their bodies to live in multiple hosts, different species, and in most cases, avoid detection,” Marcquenski said.

She said the discovery of new species will help researchers better understand the diversity of the environment in the Mississippi River.

“The more we can learn about the whole animal, not just what food, shelter, water quality do the fish species need, but also something about the parasites and pathogens that are able to infect them, it just helps us understand the whole ecosystem,” Marcquenski said.

Leis said more research is needed to understand the lifecycle and seasonal changes in the newly identified parasites. But he’s already working to describe several other new species he’s discovered and submit them for publication.

“There’s such a diversity in the habitats of the Mississippi River that allow for a lot of different species to flourish,” Leis said.

He previously identified two new species of parasites living in catfish in the Mississippi River.