top-down view of a great pond snail lymnaea stagnalis crawling on a submerged stone on a summer day

animal aquatic biology brown canal closeup crawling day ecology environment flow freshwater gastropod great green helix invertebrate lake large little lymnaea mating mollusk nature nobody one pond reflection ripple river shell slime slimy slow small snail spiral stagnalis stone stream submerged summer surface top view warm water weed wet wild wildlife yellow