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One of the continent’s oldest living creatures has been found in the mud above a Wisconsin dam.
It’s a type of mussel — a very big one that looks a lot like an Idaho potato.
The spectaclecase mussel is known for having a lengthy lifespan, but the Wisconsin Department of Natural Resources says it has found a bunch above the St. Croix Falls dam that are at least a century old.
“Native mussels can live a long time, but these mussels were pushing the limits,” Wisconsin DNR biologist Lisie Kitchel said in a news release.
“Finding some alive was amazing since the host fish species needed for their reproduction have been prevented from getting upstream as a result of the St. Croix Falls dam built in 1907.”
Prior to this, “the oldest documented spectaclecase was thought to be 70 years old,” according to the U.S Fish and Wildlife Service.
State biologists collected the mussels in August with a team that included experts from the University of Minnesota and the National Park Service. The age estimate was announced Dec. 1, and it’s based partly on when the cluster got stranded above the dam, officials said.
Several shells from dead mussels were also collected at the site “and will be cross-sectioned this winter to verify their age.”
The live mussels were put back and steps are underway to “preserve their genetic stock while they are still alive,” the state said.
Spectaclecase mussels are known for an elongated shell that can reach 9 inches, the USFWS says. They were once found in 14 states, but survive now in only three, the USFWS says.
Among the challenges the endangered mussels face is a dependence on mooneye and goldeye fish to propagate, experts say. Their larvae “must attach to the gills or fins of a specific fish to continue developing into a juvenile mussel before dropping off,” the state says.
“These species are not present above the dam but are found downstream. That means reproduction can occur downstream, and surveys have found younger spectaclecase downstream,” the state reports.