Bulimnea megasoma and Lymnaea stagnalis, Michigan. Several Bulimnea megasoma (upper left) and several Lymnaea stagnalis (upper right) were maintained for months in the same aquarium. After a while, numerous young appeared which seemed to be intermediate in shell characters between the two species. However, on electrophoretic analysis, the young were found to be all offspring of Bulimnea megasoma. Their change in appearance was due to the changed environment in which the offspring snails were born and matured. Such offspring would be called ecophenotypes.
John B. Burch (photographer; copyright holder), Mollusk Division, Museum of Zoology, University of Michigan-Ann Arbor