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.

Classifying Seashells

Marine mollusk variety

I am not in love with science.  I call my shells by their common names and pay little attention to the Latin names and don’t really care which “family” they belong to, but I realize that some people might.

So this is my attempt to explain the classification of seashells, beginning with the “Class”.

The variety of sea shells is amazingly huge.  I can’t imagine having to organize shells into groups and since the same types can look very different depending on their colors, size and age, but each type has been assigned a “class”.

The class is fairly simple to figure out since each has it’s obvious differences.

Gastropods : Snail type shells that curl around and are all in one piece (univalves).
Bivalves: Shells that come in two parts, such as a clams and oysters.
Cephalopods: Mollusks without shells (mostly – the nautilus is a cephalopod), such as the squid and octopus.
Tusk Shells or Scaphopods: tusk or tooth looking shells.
Chitons: Flattened and plated, very primitive looking.

Sand dollars, sea urchins and sea cucumbers are Echinoderms and not mollusks or seashells.

The Red Abalone

The iridescent inside surface of a red abalone...
Image via Wikipedia

Abalones live where the rocks are, near shore or sometimes in quite deep water, and move around on a large, muscular foot.  This is the best reason I can think of for not finding them in Florida – not many rocks.  I’ve never seen one here, nor are they mentioned in my seashell ID book.

They are collected to use as food and of course the shell is used for it’s ornamental value.

The Red Abalone (Haliotis rufescens) is the largest of the species growing to 12 inches (30.5cm) long.  The outer shell is dark, brick red and the inside has a beautiful iridescence.

The Abalone is prone to Withering disease that causes it to eat itself which causes the muscular foot they use to hold onto rocks, to wither, which in turn causes them to fall off and eventually starve to death, unless a predator gets them first.