Speaking “Seashell” Means Delving Into the Life of Mollusks

In my Florida life, a seashell was a seashell.  Some were prettier than others, some were larger and I just called them shells and never knew they were actually mollusks.  In fact, when I found a nice shell, I never gave much thought to what had once lived inside.

seashells in a big round bowl
My Seashell Collection

Now I have learned to speak seashell. At least to the degree that I know the difference between a gastropod and a bivalve and that animals in the phylum mollusca inhabit most every area of the earth, although I write about the marine mollusks, the ocean-dwelling ones. (In England mollusk is spelled “mollusc”.)

Fighting Conch – Gastropod

Mollusks are invertebrate animals and I am mostly interested in the ones that live inside their shell homes, but some mollusks don’t have shells (squid, cuttlefish and octopus).  They consist of single shells that are all in one piece – gastropods or univalves, and shells that are hinged, or two pieces – bivalves.  They all live in ocean water or brackish water, which is less salty as it is combined with fresh water.

disc dosinia seashells
Disc Dosinia Seashells – bivalves

I mainly use the common names of the shells when describing them, but the scientific names are important in identifying seashells and each shell will have a two-part name.   Always the scientific name is italicized, with the first part being capitalized and the second is not.

Below is a beautiful Knobbed Whelk shell.  Search as Busycon carica.  And read more about this one on my blog post.

knobbed whelk
Knobbed Whelk

When reading the descriptions of a gastropod on a more scientific site or in my seashell ID book, I learn about the spire (top part of the shell), whorl (the way it twists), aperture (opening), lips (edges of the opening), canal, and operculum which seals the “door” when the animal retreats inside it’s shell.  The bivalve descriptions could include describing the umbones, ligament and hinge teeth.  Most descriptions will include colors and characteristics unique to that shell and the inside color along with the size and where it can be found.

Once you know this, you can speak seashell too.

How Is A Seashell Made?

Cypraea chinensis with partially extended mantle.
Image via Wikipedia

A mollusk is the animal living inside a shell.  All mollusks begin as tiny creatures with genetic programming telling it how it will look – basically.  Just like we have characteristics of our parents, the shell begins life looking like it’s ancestors.

As the snail inside grows, the mantle continues to add calcium carbonate and conchiolin to the outer surface of the shell to expand it. Because the mantle is constantly rubbing the surface of the shell it becomes smooth and sometimes very shiny. The shells hardness and colors come from the calcium layers deposited by the mantle. The mantle is also responsible for creating the shape, spines and grooves in the shell.

The mollusks choice of food and habitat also may contribute to it’s coloring. As it grows and moves about feeding and doing what mollusks do, it is all the while creating a beautiful work of art unlike any we could ever duplicate.

Please respect all living mollusks and observe them in their habit, but leave them alone – as I’ve said in a previous post, take your camera to the beach.

Reference: Sanibel Seashells Blog

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