OBSERVATIONS OF NON-LAMPSILINE UNIONID MANTLE DISPLAYS AND GLOCHIDIA RELEASE

Bernard E. Sietman, Minnesota Department of Natural Resources
Mike Davis, Minnesota Department of Natural Resources, Division of Ecological Services
Mark C. Hove, Macalester College, Department of Biology

Freshwater mussels have evolved impressive strategies to promote the transfer of glochidia to their hosts. Among these, modification of the mantle as a host attractor or lure is the most well known. Members in the Tribe Lampsilini are the only group with published accounts describing such lures. We document for the first time mantle modifications in non-lampsiline unionids presumably used to attract host fish. We observed mantle displays in five species, Cyclonaias tuberculata, Quadrula fragosa, Q. metanevra, Q. pustulosa, and Tritogonia verrucosa, all of which are members of the Tribe Quadrulini, a monophyletic group within the subfamily Ambleminae. Displaying individuals contained mature glochidia, which were occasionally released when the display was touched. Cyclonaias tuberculata and Q. pustulosa, had similar displays, while the displays of other species were different in appearance. Displays were static, but appeared to be enlarged at night for T. verrucosa. These structures do not appear to mimic known aquatic animals, e.g. minnow, but might resemble a novel food item to entice a fish strike, or perhaps is associated with the release of a chemical attractant.

Suggested reading

Haag, W.R., and M.L. Warren, Jr. 1999. Mantle displays of freshwater mussels elicit attacks from fish. Freshwater Biology 42:35-40. Haag, W.R., M.L. Warren, Jr., and M. Shillingsford. 1999. Host fishes and host-attracting behavior of Lampsilis altilis and Villosa vibex (Bivalvia: Unionidae). American Midland Naturalist 141:149-157.