I have collected some shells and pieces of shells that are full of holes or have crazy lines etched in the top. Sometime a shell will have a perfect hole all the way through it, just as if it was meant to be hung on a wire to make a pretty necklace. I never knew what caused these phenomenons until I read about “Shell Wars” in my new reference book, “Florida’s Living Beaches, A Guide For the Curious Beachcomber” by Blair and Don Witherington. In the mollusk section of the book they explain how some gastropods will bore holes through the shells of others to feed on them. In doing so, they leave a hole, or sometimes lots of holes as in the case of boring sponges that use acid to digest shells and actually leave them looking like a sponge – full of holes.
You can see in my picture on the left that one of the cockle shells has a hole at the top and in the photo on the right there are plenty of examples of shells that have been changed into porous looking shapes and no longer resemble seashells.
When you find a beautiful shell on the beach, do you ever think about the creature that used to live inside? If you are like me, probably not. At least, I never did until I began to study seashells. I will never look at shell collecting the same way now that I can imagine the snail like animal moving about the ocean floor carrying his shell along, searching for food. Sometimes that food is another mollusk.