Our fascination with seashells likely began when we were children, encouraged by our parents to hold the shell to our ear and listen. What we heard was the faint and continuous sound of a mysterious and distant ocean. As we age, the fascination doesn't go away, and we start to appreciate the diversity of colors, intricate patterns and interesting texture.
Beachcombers everywhere spend hours inspecting and sifting through the sand with such patience and devotion that one would think they were panning for gold. There is no doubt, seashells are treasured as magnificent organic art, but wait a minute - where do the shells come from?
Amazingly, they are the intentional masterpiece of animals known as mollusks. These include snails, clams, mussels and even the squidlike chambered nautilus. Generally not at the top of anyone's list of favorite animals, these often small, slimy and slow creatures are easily overlooked.
Article Photos
An estimated 20 percent of mollusks found in Hawaii are found nowhere else in the world. This is a Tiger Cowrie (Cypraea tigris schilderiana) fully covered by its mantle skin.
KEOKI STENDER photo
Instead, it is the shell itself that captures our attention. Each species of mollusk creates its own unique shell, and as the second largest group of invertebrates (animals without backbones), there are literally tens of thousands of different shells around the planet.
The main purpose of the shell is protection against predators, and it is in a constant state of growth. Unlike hermit crabs that recycle an empty shell, swapping it for larger ones as they grow, mollusks have the same shell for their entire lives. They maintain their shell like a neat little construction site, building it like we would build a wall, except this tiny boneless soft-bodied animal uses secretions from a skin layer known as the mantle.
As the animal grows, it secretes proteins and minerals adding layer upon layer to its home. First is the outer layer, or periostracum, which consists of a protein called conchiolin. This protein stiffens and gives the snail a sort of foundation, a strong matrix on which to add the next layer. This strengthening protein is even used by cosmetic companies in their moisturizers and conditioners. Next is the drywall layer, called the prismatic layer, which is thicker and made of calcium carbonate, the same ingredient found in rock, eggshells and chalk. This is where the shell pattern and pigmentation is created. The paint layer, the lamellate, is the smooth part inside the shell. Made of a crystallized form of calcium carbonate called nacre, it scatters light giving the shell the iridescent look that is known as mother of pearl.
When a mollusk dies, all that is left behind is its shell. This beautiful skeletal remnant will drift and roll with the ocean's rhythmic motion. However, a vacant shell is a valuable find for a hermit crab that can't survive without it, and just like that the shell commences its second life.
By the time we find the shell washed up on the beach it may look a little worn, but hold it to your ear and you can enjoy that reminiscent sound of the ocean. Then, being a responsible steward of the sea, return the shell to the ocean knowing it is still a valuable part of the marine ecosystem.
* Erin Iberg is the community education manager at the Maui Ocean Center. "Ka Mo'olelo Moana," or "The Ocean Story," is a monthly column submitted by the Maui Ocean Center, which is open from 9 a.m. to 5 p.m. daily in Maalaea. For more information, call 270-7000.
