Re: Do snails have to change there shells, or stay in the same one?

Hi Tina,

Snails live in a single shell their entire lives. The shell grows along with the animal's body. The parts that can be extended from the shell (head and foot) occupy the largest whorl of the coiled shell, while the softer parts (visceral mass and gonads) occupy the smaller whorls.

In fact, a snail is permanently attached to its shell, and couldn't leave even if it wanted to. A muscle called the columellar muscle attaches to the columella of the shell, which you can think of as the central axis around which the shell coils. If you were to dissect a snail, you'd find that most of the body slides easily through the interior of the shell, except for a muscular bit of tissue attached somewhere in the middle of the shell. This page has some nice diagrams of snail shell anatomy. It also has links to other aspects of snail biology, which might interest you.

Allison J. Gong
MAD Scientist

Additional reference:
Brusca and Brusca, 2003. Invertebrates. Sinauer Associates, Inc.
ISBN 0-87893-097-3