Soil CaCO3 levels were determined for six ecosystems in Washtenaw and Wayne Counties, Michigan and in Linn County, Iowa; and correlation between these results and the shell thickness of certain terrestrial snails was made. Species used were Anguispira alternata (Say), Triodopsis multilineata (Say), and T. albolabris (Say). Two ecosystems had high CaCO3 levels (120-144 ppm), three had intermediate levels (93-99 ppm) and one had a low level (40 ppm). Width/thickness ratios of live and cast shells showed that those in high calcium ecosystems had thicker shells than those in low calcium ecosystems, though there were large deviations in the thickness values. Population density of the snails seemed to be influenced by the calcium level, but predators, cover, and moisture conditions were also observed as important limiting factors. Species distribution studies showed that the maximum number of species was found when soil CaCO3 levels were between 99 and 120 ppm, with a decrease in number of species in low calcium ecosystems. These correlations seem to indicate that at some point in the food chain of the terrestrial snail, calcium is passed on to the snail at levels reflecting the levels of calcium in the ecosystem.
Proceedings of the Iowa Academy of Science
©1966 Iowa Academy of Science, Inc.
Atkins, Charles G.
"Factors Affecting the Structure and Distribution of Terrestrial Pulmonata,"
Proceedings of the Iowa Academy of Science, 73(1), 408-416.
Available at: https://scholarworks.uni.edu/pias/vol73/iss1/60