Comparative Studies of Five Populations of North American Limpets. Andrea Walther, University of Michigan, School of Natural Resources and Environment; home address: 4873 Packard Road, Apt. B5, Ann Arbor, MI 48108 Freshwater pulmonate limpets (Basommatophora) are easily recognizable by their nearly bilaterally symmetrical, cap-shaped shells that lack the coil so commonly associated with the great majority of gastropods. Because of their small size and inconspicuous nature, these common invertebrates have received little attention. Belonging to the family Ancylidae, Laevapex is a genus of these tiny snails that may be found throughout the eastern United States and is second only to Ferrissia in the extent of its range. Depending on the species, Laevapex may inhabit either lentic or lotic habitats and generally attach to rocks, decaying leaves, fallen timber, and aquatic vegetation. Samples of Laevapex were collected for this study from Pickerel Lake in Michigan, New River and South Anna River in Virginia, and the White and Cossatot Rivers in Arkansas. Three species are involved: Laevapex fuscus, Laevapex diaphanus, and Laevapex arkansasensis. The objectives of my study were to determine the validity of the species and h ow they are related using a comparison of internal and external anatomy, chromosome numbers, and molecular characters.
