How Is a Seashell Made?

A seashell is the exoskeleton of some species of mollusks that live in fresh water or the sea. The shell is secreted by the mantle or epidermis of the organism, according to Scientific American.

The Mantle

The mantle or epidermis of the mollusk secretes proteins and minerals which gradually create the shell. As the mollusk grows, it enlarges the shell from the bottom up, or builds it up at the outer margins.

Different Layers

A seashell consists of an uncalcified outer protein and chitin layer that binds calcium. The calcified middle layer builds up under it, and finally, the bottom or inner calcified layer called the nacre.

Shape of Shells

The binding of calcium to the protein layer causes calcium carbonate to build up in predetermined patterns. This process appears to be guided by the timed secretion of different proteins, resulting in species-specific shells.

References

• Scientific American: How are seashells created?