A mollusk is the animal living inside a shell. All mollusks begin as tiny creatures with genetic programming telling it how it will look – basically. Just like we have characteristics of our parents, the shell begins life looking like it’s ancestors.
As the snail inside grows, the mantle continues to add calcium carbonate and conchiolin to the outer surface of the shell to expand it. Because the mantle is constantly rubbing the surface of the shell it becomes smooth and sometimes very shiny. The shells hardness and colors come from the calcium layers deposited by the mantle. The mantle is also responsible for creating the shape, spines and grooves in the shell.
The mollusks choice of food and habitat also may contribute to it’s coloring. As it grows and moves about feeding and doing what mollusks do, it is all the while creating a beautiful work of art unlike any we could ever duplicate.
Please respect all living mollusks and observe them in their habit, but leave them alone – as I’ve said in a previous post, take your camera to the beach.
Reference: Sanibel Seashells Blog