Marine Creatures of the Northern Gulf – Snails and Slugs

Snails and slugs belong to one of the largest phyla of animals on the planet – the mollusks.  Mollusks are known for their calcium carbonate shells and seashell collecting along the shoreline has been a popular hobby for centuries.  There are an estimated 50,000 to 200,000 species of mollusk worldwide.  One group – the gastropods – have an estimated 40,000 to 100,000 species alone.  This is the group that includes the snails and slugs.

Snails are soft-bodied creatures who produce a single, usually coiled, shell in which they live.  The coiled shell has an opening called the aperture through which they can extend some, or most of their body.  The elongated soft body “slugs” across the sea bottom searching for food which could be vegetation for some – like the small nerite snails found in our bays, or animals – like the venomous cone snails, or detritivores – like the periwinkle snails.

Many species of local snails produce egg cases in which they deposit their developing eggs.  These are often found while people are beach combing.  The most frequently encountered locally are the tube-shaped clusters of the oyster drill, the coin shaped chain of the lightning whelk, and the one that – to me – resembles the top of a vase or jar belonging to the moon snail.

The variety of snails found in the northern Gulf is immense – so, we will cover only a few of the more common.

Walking along the Gulf side, gazing down at the shells of snails washed ashore, one often finds the small ceriths.  These tiny, elongated shells are small and look like a canine tooth.  These are herbivores and detritivores.

The Florida Fighting Conch is often found – but not always in whole condition.  This is a true conch and herbivorous.

One not as common while beachcombing, but more common while snorkeling is the olive snail.  These are fast burrowing snails that feed on bivalves and carrion they may find.  I often find trails crisscrossing the sandy bottom made by these snails just off the beach.

Over on the bay side of the barrier islands you have a better chance of finding live snails.  One of the more common in the salt marshes is the marsh periwinkle.  This small roundish snail is often seen on the extended leaves of the marsh grasses.  It is here during high tide to avoid predators such as blue crabs and diamondback terrapins.  At low tide they will descend to the muddy bottom and feed on detritus.

The crown conch is another frequently seen estuarine snail.  With spines extending from the top whorl – it appears to have a crown, and where its common name comes from.  These are predators of the bay feeding on other mollusks such as periwinkles and oysters.

The oyster drill shell is one of the more common shells you find hermit crabs in, but the snails are out there as well.  As the name implies, they use a tooth like structure called a radula to bore into other mollusk shells to feed.  They are particularly problematic for non-moving oysters – and where they got their common name from.

The only slug I have encountered on our beaches is the sea hare.  These slugs can be a greenish or brownish color and are about six inches in length.  They lack an external shell but do not move much faster than their snail cousins.  They feed on a variety of seaweeds and the color of their skin mimics the seaweeds they are feeding on.  Lacking a shell, they produce a toxin in their skin to repel would be predators.  They also release ink like the squid and octopus cousins.

This narrative only scratches the surface of the world of snails and slugs in this part of the world.  Creating a check list of species and then seeing if you can find them all is great fun.

 

 

References

 

The Mollusca. Sea Slugs, Squids, Snails, and Scallops. University of California at Berkley. https://ucmp.berkeley.edu/taxa/inverts/mollusca/mollusca.php#:~:text=Mollusca%20is%20one%20of%20the,scallops%2C%20oysters%2C%20and%20chitons..

 

Gastropods. University of Texas San Antonio. https://www.utsa.edu/fieldscience/gastropod_info.htm#:~:text=Gastropods%20are%20another%20type%20of,of%20the%20entire%20Mollusca%20phylum..