Substrate preferences of Campeloma decisum and Elimia livescens: influence of species interaction and substrate tenacity.

Abstract

This investigation sought to examine if substrate choice among the freshwater operculate snails Campeloma decisum and Elimia livescens in Douglas Lake, Cheboygan County, Michigan could be explained by species interaction or substrate tenacity. In Douglas Lake, C. decisum are found primarily on sandy substrate (125 total snails, 95 collected on sand), while E. livescens are more prevalent on rocky substrate (107 total snails, 80 collected on rock). The snails maintained this substrate selection in laboratory conditions. Substrate choice in the lab was not influenced by whether the snail species had been collected on rocky or sandy environments. When we placed the two species together in the same aquarium, we found that the presence of the other species did not sway substrate selection. Because their substrate choice was the same in the presence or absence of the other species, we were led to believe that neither interspecific competition nor other speices interactions are factors of substrate choice. In the presence of artificial waves, species differed in their ability to maintain position on the two substrates. C. decisum was better able to keep from being dislodged on sandy substrate, while E. livescens did better on rocky substrate. We can thus infer that C. decisum is better at burrowing into sandy substrate than E. livescens, who can more adequately grip onto rocky substrate. Wave presence can therefore be an environmental factor contributing to substrate preference of the two observed snail species, due to the specialized biological and physiological characteristics of these species. There is a non-random relationship between the operculate snail species C. decisum and E. livescens and their substrate preference in different sites in Douglas Lake.