BIO 203



          This is a tongue-like organ that is found throughout the phylum Mollusca, except in bivalves(Hickman et al, 2007).  The radula is a ribbon like membrane with rows of chitinous teeth mounted upon it (Hickman et al, 2007).  It is used for rasping and grinding substrates off surfaces (Hickman et al, 2007).


          This serves as both a method of locomotion and attachment (Emberson et al, 1994).  This structure creates a creeping motion due to waves of muscular contractions (Hickman et al, 2007).   These contractions go from the posterior to the anterior of the bottom of the foot (Emberson et al, 1994).   While moving, a mucus is secreted that aids in the adhesion to whatever surface the snail is moving on (Hickman et al, 2007).  The downside to the mucus is that the adhesiveness of the mucus has to be overcome in order for the snail to continue moving (Emberson et al, 1994).  This action comes at a great cost of energy (Emberson et al, 1994).


          This is a durable proteinaceous plate that conceals the shell aperature after the body retreats into the shell (Hickman et al, 2007).  The operculum serves two function; it can provide protection for the body, and it can also prevent dessication (drying out) (Burch, 1962).  This adaptation has allowed some species of snails to be inactive for years until moistened again (Burch, 1962).

Pulmonate (lung)

          Terrestrial species of have evolved to have a vascularized mantle wall which functions as a lung instead of using gills (Hickman et al, 2007).  Both the anus and nephridiopore open close to the pnuemostome (lung opening) (Hickman et al, 2007).