Tag Archives: Gastropods

Seashell Speak

Shells קונכיות
Image via Wikipedia

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.

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”.)

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.

I mainly use the common names of the shells when describing them, but the scientific names are important and each shell will have two parts to it’s name and it is always italicized with the first part being capitalized and the second is not. I don’t know why, and forgive me if I sometimes don’t include the scientific name, but searching for information about a certain shell is easier when using it. That is when you will come across the more scientific sites – which this blog is not.

When reading the descriptions of a gastropod on a more scientific site, you will read 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.

It is difficult to find a lot of information and good photos online, and if you really want to study seashells, I suggest buying a book about shells in the area you plan to be beachcombing.

Seashell Markings and Bore Holes

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” 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 Tropical Treasures New Address Postcards postcard
You can see in my picture on the left that one of the cockle shells has a hole at the top and in the photo on the right there are plenty of examples of shells that have been changed into porous looking shapes and no longer resemble seashells.

When you find a beautiful shell on the beach, do you ever think about the creature that used to live inside? If you are like me, probably not. At least, I never did until I began to study seashells. I will never look at shell collecting the same way now that I can imagine the snail like animal moving about the ocean floor carrying his shell along, searching for food.  Sometimes that food is another mollusk.

The Mighty Florida Horse Conch

The Florida horse conch (Pleuroploca gigantea)...
Image via Wikipedia

The Florida horse conch (Pleuroploca gigantea) seashell is the state shell.  With all the seashells found along the many beaches in that state, do you ever wonder how they chose just one and why?  Sorry, but I don’t know the answer – if I find out I’ll post it here – but I imagine because it is one of the largest gastropods in the world!

My ID book says that the mollusk can grow up to 19 inches in length, but other sites have said up to 24 inches!

They are carnivores and eat other large gastropods, such as the Murex, Lightning Whelk, Tulips, Oysters and others. They use their proboscis to eat the meat out of the shell of their prey.

The “i love shelling” blog has a great photo of a smaller horse conch eating a lightning whelk, in the post entitled: Feeding Frenzy!

Many states have also chosen a specific mollusk as their state shell.  View the list here.

A Huge Sanibel Whelk Found on Easter

The Frog Shell

Granulate Frog Shell - Bursa granularis

The frog shell is not extremely pretty as it tends to be covered in “limy deposits”.  The St. Thomas Frog Shell (Bursa thomae) got it’s name because it was first discovered in St. Thomas in the Virgin Islands. It’s a small shell, growing only to a little over an inch long.

Another frog shell – the California Frog Shell (Bursa californica) is commonly found in Baja California where it is frequently pulled up in crab and lobster traps. This species is larger and can be up to 5 inches in length.
Info taken from National Audubon Society’s Field Guide to Shells

See another photo of a frog shell – The Yellow Mouthed – here.

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.