Shell of a Ramshorn snail. This provides protection and support for the snail. Photo courtesy of Rob Dillon
Helisoma trivolvis is in the Phylum Pulmonata. This means that it lacks gills and has lungs formed from it's mantle cavity. Pulmonate snails are capable of trapping an air bubble in their mantle cavity and this can be seen as an adaptation to warmer waters, where there isn't as much dissolved water available (Dillon, 2006). The air in it's shell makes it buoyant, and they are able to go down to different depths in the water by letting out gas. (Dillon, 2006). As you saw in the habitat page, all of the areas where these snails are found would be suitable for this. These snails also have well developed circulatory systems and nervous systems to be able to carry nutrients throughout the body sufficiently. All snails have soft bodies but not all of them have shells like Helisoma trivolvis. A shell helps protect their body and has other important funtions as well, such as helping support the body, and helping the snail to float. (Heckman, 2009). There are lots of different types of snails that have shells besides the ramshorn snail.

Next see the nutrition page where you can learn about other features these snails have in order to get their food.