Seashell Markings and Bore Holes

cockle shells and arks

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” (affiliate link to Amazon), 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.
Black and White Cockle Shells Postcard postcard

cross-barred venus clam
Shells with bore holes

How Are The Bore Holes Made

Meat eating mollusks will eat other mollusks and one way they do that is to bore a hole into the shell and suck out the snail inside.

With their tongue, or radula, they create the hole with the help of enzymes from their own body which soften the shell. They use their radula as a drill, and make the hole.

This is why some shells look like a hole was drilled perfectly into the top. That sea snail was killed by another snail.

Considering Sea Snails, There is Lots to Learn

When you find a beautiful shell on the beach, do you ever think about the creature that used to live inside?  They are interesting organisms and the shell homes they create are even more so.  Each mollusk makes it’s own type of shell, and within those varieties can be more varieties.  Each seashell is unique, which is why we love collecting them so much.

Now that I have a boat, and can get out to the islands along the Indian River waterway, I’m constantly looking for unique mollusks and their seashells.  Sometimes I even get to find a living shell like this huge horse conch and beautiful fighting conch.

I see plenty of empty shells with weird markings too, but now I know why they are there.

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12 thoughts on “Seashell Markings and Bore Holes

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  10. Mickey H

    Thanks for your hard work & info on shells. I’ve learned a lot myself in the last year, since becoming a volunteer at the Clearwater Marine Aquarium (home of “Winter, the dolphin” where I give tours, work at the touch tank, and work on the Marine Mammal Stranding Team. All new subject matter for this former music teacher and “still new” (2 yrs) resident to FL. Now whenever we go to the beach or even to any body of salt water, I’m always looking for the critters which reside in those waters. And like any enthusiastic teacher, I hunt down people of any age to show them what I found and educate them. Your website has given me more knowledge to take back for when I work at the CMA touch tank. Thanks again!

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