Mesodon clausus
Adaptations
A Snail's Shell
The shell is secreted by glands in the snail's mantle and is comprised of three layers:
1. The hypostracum - This is the innermost layer. It is the closest to the snail's body.
2. The ostracum - This is the middle, shell building layer. It is comprised of prism-shaped, calcium carbonate crystals and other organic molecules.
3. The periostracum - This is the outermost shell layer. It consists of conchin, which is a mixture of organic compounds, and gives the shell its color.
A terrestrial snail's shell is primarily responsible for protecting the snail's internal organs, preventing water loss, providing shelter from cold, and protecting the snail from potential predators. When the weather becomes inclimate, the snail will take the required measures to survive. (See Snail Estivation and Hibernation)
Snail Movement
The snail moves via a muscular foot. Terrestrial snails secrete a layer of slime, or mucus, from a gland in the front of the muscular foot. The mucous allows the snail to glide more smoothly over all different types of surface, and also helps to form a suction that enables them cling to vegetation and even hang upside down!
Snail Senses
Sight: Terrestrial snails have very simple and primitive eyes called eye spots. These eyespots are located on the tips of the snail's long, upper pair of tentacles. Snail eyes are not complex and provide them with more of a general sense of relative light and darkness in their surroundings, rather than a distinct image.
Hearing: Snails do not have ears in the traditional sense. They use their bottom set of tentacles to sense sound vibrations in their surroundings.
Touch: The short tentacles located on a snail's head are very sensitive to touch sensations and are used to help the snail build a picture of its environment based on feeling nearby objects.