These three specimens demonstrate the diagnostic differences in the shells of their two families. Stagnicola caperata , Nebraska. This is a common freshwater snail of the western plains, living in streams and semi-permanent ditches. Note the narrow connection between the head-foot and viscera. Determining reproductive compatibility.
Some disjunct populations differ consistently in one or more characters.
One test that has been applied is reproductive compatibility. In hermaphroditic animals capable of self fertilizing, such as pulmonate snails, special precautions must be taken to prevent selfing. The protocol shown here is such an experiment, where individuals of two populations were tested for reproductive compatibility. They turned out to be incompatible, i.e., reproductively isolated. The ADW Team gratefully acknowledges their support.