Seashell Formation

Seashell Formation

Any talk about the great seashells and shelling that happens on Sanibel and Captiva islands must start with how seashells form and what they are made from.   Technically, seashells are just the outer exoskeletons of a large varied group of animals called mollusks.  Similar to a human skeleton growing along with us, a seashell grows with the mollusk inside.  The animals form protein and mineral based secretions that when secreted a thin layer is added to the seashell.  Just like a human is unable to shed their skeleton, a seashell is unable to shed their shell.  As the mollusk grows the seashell must grow to accommodate it.  They are made mostly of calcium carbonate.  Sometimes a seashell will have a hermit crab living in it.  Hermit crabs do not create the seashell but find emtpy ones about their size to move into and protect their soft vulnerable bodies