Luring a Host
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The mantle display of a female yellow lampmussel (Lampsilis cariosa). Photo by Phillip Wick

Some species of freshwater mussels go to extraordinary lengths to attract fish hosts for their larvae.

In the summer, the female yellow lampmussel, one of two threatened mussel species in Maine, develops a fleshy growth that protrudes through the opening of its shell. The growth looks like a minnow and even has a dark spot where an eye would be. The other end of the growth is shaped like a tail, which the female mussel can wave back and forth in the water.

"You would swear it was a real fish, but it's just a lure designed to attract a fish predator," says Judith Rhymer, an associate professor of wildlife ecology at UMaine who is leading several studies of freshwater mussels.

"When a fish comes along and chomps down on the lure, it triggers the mussel to release her larvae into the fish's mouth."

The larvae attach themselves to the fish's gills, where they stay until they are mature enough to drop off and survive on their own.

"The fish lures are an amazing evolutionary adaptation," Rhymer says. "Some species of mussels don't use lures, but among those that do, there is a remarkable variety."