Posted by: Doc Bruce | April 6, 2007

Is That a Snake on the Beach???

This time of year, we get that question a lot at Sanibel Sea School. And yes, perhaps if you are prone to see snakes, or even a little fearful of snakes, one might think this specimen to be a snake. But snakes are not really all that common on Sanibel Island’s beaches.
These are really strings of egg cases from the gastropod mollusk, the Lightning Whelk. Gastropod mollusks are those invertebrate animals that form a single shell in which they live. They increase the size of the shell as they grow; they are sometimes called univalves. Lightning whelk females create these strings of individual egg sacks and attach them to the bottom of the ocean. The developing animals within them make a small shell known as a protoconch and when they are ready to be out on their own they crawl out a small hole in the egg case and into the sandy bottom where they live and grow into larger, juvenile lightning whelks.
The egg cases become dislodged from the substarte and wash ashore this time of year.
Unfortunately, some of the egg cases wash ashore before the young have had an opportunity to crawl out of the egg cases. When this happens we are blessed with the opportunity to dissect the individual egg cases and collect the tiny protoconchs. Often each egg case has between 20 and 35 protoconchs and many strings of egg cases have 50 individual egg cases. This tells us that mnay of these females have between 1000 and 1750 offspring!
So, go ahead and pick up that egg case, look to see if you can find one with dried protoconchs. You might just be blessed with another treasure from the sea!


  1. Sounds like the kids are having fun with lots of things to learn every day. Make sure that Emma can spell all those big words, her brother will be testing her when she comes home.Thanks from her Mom, for such a wonderful opportunity this week.

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