Only then are they capable of filter-feeding and living an independent existence. Glochidia must reach a suitable host fish or die, but they cannot swim or even crawl. Their entire behavioral repertoire consists of the ability to clamp their bivalved shell, like a tiny bear trap, onto the filament of a fish's gill. These packages are released from the female clam along with the water leaving the gills. A sticky thread trails behind and attaches the lure to a rock or stick, where it twirls invitingly in the current.
Most mussels are able to use only one or a few kinds of fish as host.
We immediately suspected darters, which are characteristic and colorful denizens of riffles in Ozark streams. Sure enough, of the 12 species of fish that we tested as hosts, only darters were able to support the development of the kidneyshell's larvae to the juvenile stage. Certain other Ozark mussels attract fish hosts for their larvae by displaying a lure that is part of the female's body. These lures can appear remarkably fishlike, complete with eyespots, fins and an inviting wiggle. When a predatory fish strikes at the lure, the female clam expels a cloud of glochidia into the water.