Adaptation
Radula
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).
Foot
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).
Operculum
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).