Have you thought much about the life story of the pretty mollusk shell you discovered on the beach? The shell is actually the empty house (exoskeleton) that protects a living animal much like ourselves – one with circulation, respiratory, nervous and digestive systems.
And, guess what? The occupants get hitched and lay eggs and have babies and try to survive, just as we humans do.
How does this animal grow up? An amazing organ called the “mantle” does most of the work.
Although some dispute a mollusk having a brain, who needs a brain when you’ve got a mantle? It is a magical cloak that surrounds the body with pockets to store organs and eggs, and it regulates the whole household, but its most important job is being a master architect.
As the animal inside the shell grows bigger, the mantle goes to work being the house builder. It takes calcium minerals from the ocean water and secretes calcium carbonate and conchiolin to build the shell extensions on the home.
There are even three walls, the inner often pearly and the outer resilient and often highly decorated. If the shell home gets damaged, the mantle is ready to do any repairs.
You might notice the growth rings on a clam indicating shell additions or look at the tiny top of a whelk or other snail. That’s the baby shell, the mantle adding more material with turrets, spires and coils to accommodate a growing occupant. The mantle even makes the different colors and patterns on the shell – and some scientists even pose that it might help shell communication.
We are fortunate to live near the ocean. The beach is a treasured ecosystem of animals living on and beneath the sand with eggs and larvae and plankton floating in the waves. We need to protect all of it!
There is current concern that atmospheric CO2 is dissolving in the ocean at an alarming rate. It is forming carbonic acid which reduces the availability of calcium carbonate, therefore reducing the ability of the mantle to form shell material.
A good book to learn more about beach life is “Living Beaches of Georgia and the Carolinas” by Blair and Dawn Witherington. You can also sign up for a beach discovery walk or catch a program at the Coastal Discovery Museum on Hilton Head Island.
By the way, there is one beach critter who rents a shell home rather than being a permanent resident. Do you know who this hobo might be?
You might think you have found an empty shell, but look closely and if you see some feet trying to hide, be sure to put the rental with the crabby tenant back in the surf.
The same consideration goes for all living shells, as they deserve to live and reproduce and enjoy time on the beach just as we humans do.
Debby Boots is a master naturalist, docent with the Coastal Discovery Museum, and author of a small cookbook titled “Cattail Cakes and Chickweed Snakes.”