By: Ani Popp, GA DNR Nongame Conservation Section
Did you know freshwater mussels have a parasitic life stage? Larval mussels, called glochidia, attach to fish gills, where they stay until they transform into juveniles. The juvenile mussels then fall off the fish to the river bottom where they spend the rest of their lives—20 to 50 years!
How these glochidia attach to fish gills is a class-act case of trickery. Female mussels have developed several ways to lure fish close enough for the glochidia to be transferred—you could even say that they are fishing! After fertilization, some mussel species will pack glochidia into floating lures that are attached to the female by a mucous strand. These lures float in the water column until a fish attacks, bursting the lure and giving some of the glochidia a chance to attach to the gills. Other species have mantle lures (the mantle is the soft tissue that extends beyond the edge of the shell) that mimic prey, from insects to crayfishes to small fish!
Here, a female Southern Rainbow mussel (Villosa vibex) shows off the glochidia packed into her gills, hoping to attract an unsuspecting fish. She is using her mantle, modified to look like a small fish or clump of worms, as a lure. Can you see the dark black eyespots on the right end of her mantle?
For more information about freshwater mussels, check out the Mussels of Georgia webpage and the Freshwater Mollusk Conservation Society. Thanks to Matt Hill for the excellent video footage below!