A Shell is Not Just a Shell

September 30, 2015

Did you know that seashells can serve as calendars and journals?! If you're wondering how that's possible, look at the ridges on the shell. Notice the different sizes of the ridges.

These reveal the times when they grew very fast and times when they grew slowly. Now look in between the ridges for even smaller ridges. The smaller ridges represent times when the animal living in the shell had plenty of food or a lack of food. (Yes, molluscs eat!) Most of the animal’s food tends to be available during the highly productive times of year, usually early spring and late summer. Less productive times of year produce less food. Therefore, one can conclude that the times of greatest seashell growth occurs during the spring and summer seasons.

In in the spiral on the back of a snail shell, not only can we can see the growth of the animal inside but we may even be able to follow the cycle of the moon. Anyone who studies life cycles will notice patterns of behavior affected by the moon. Certainly as a fisherman, I have noticed the feeding patterns that different fish show during this bi-monthly phenomenon. I believe the hypothesis that feeding in the ocean occurs most heavily around the full and new moon (this could be explained by the greater movement of the water). By building its home in the shape of a spiral, snails not only economize on space, they also use the approximate ratios of the golden mean and Fibonacci sequence!

When feeding occurs then growth occurs and we can observe this in shells. The next time you look at a shell, see if you can tell when Superstorm Sandy passed through the area. Would there have been a lack of food or was there plenty? How old is the shell? What can it teach you about math and time? What other information can a shell give us? The possibilities are endless.