Complex sentence: This adaptation is reflected in their life style; they are moderately amphibious, and equipped with a shell "door" or operculum enabling the snail to close itself off in the shell to prevent drying out while hiding in the mud during dry periods.
Split into simpler sentences: This adaptation is reflected in their life style; they are moderately amphibious. They have an operculum which enables the snail to seal the shell entrance to prevent drying out while they are buried in the mud during dry periods.