Common Shells of SW Florida and Keewaydin Island Beaches
Common Shells of SW Florida and Keewaydin Island Beaches
Did you know shells are made by the soft bodied animals that live inside them?
Shells are made by some types of mollusks, soft bodied animals such as snails, slugs, mussels, or octopus. Most shells are made by either a gastropod – meaning “stomach-foot”, aka snails; or a bivalve– a two-sided shell like a clam. The shell is made of calcium carbonate (chalk) secreted by the organism, and the shell is continuously grown as the organism grows.
Two sided bivalve shells, such as clams, are held together with a hinge that usually breaks apart after the creature dies, which is why you often find only one side of a shell. They use gills that filter water and function both as lungs and as a mouth for finding plankton and debris in the water to eat. Their shells are made from calcium in the water which they make into a glue to add on to the edge of their shell, expanding it a little more with each layer as they grow.
Snails grow their shells similarly, adding on layer by layer to enlarge the shell. The small sharp spiral end was the original shell when the snail was a baby. As the snail grew it added more and more calcium glue to the opening of the shell and made it larger. Most snails feed using a long straw like tongue with a sharp file at the end. They use this tongue to either scrape algae off other shells, or, more often, to drill through the shells of other mollusks. Once they have drilled through the shell, they inject stomach acid to dissolve the critter inside its shell, before using their tongue to slurp their victim out like soup. Keep an eye out for shells with perfectly round little holes in them when you are shelling!
The best way to find the most awesome shells is to take a boat trip out to Keewaydin Island. Clocking in at eight miles long, Keeywaydin is one of the longest un-bridged islands in Florida. Nearly 80% of the island is uninhabited, and the land is managed by the Rookery Bay National Estuarine Research Reserve. Rising Tide Explorers is the official ecotour partner of Rookery Bay, and offers biologist led trips to a private dock on the island where you are sure to have the whole beach (and all the shells) to yourself. Most other shelling companies only have access to the publicly accessible southern tip of Keewaydin, closest to Marco Island, and this area gets incredibly busy with tons of boaters and shellers, and the shells are well picked over as a result.
A shelling trip with Rising Tide offers exclusive access to the secluded beach strand in the middle of the island, miles away from everyone else, with a guide who is a trained biologist. During the boat ride over to Keewaydin your biologist boat captain will tell you about the ecology of the mangroves and mudflats ecosystem, the history of the area, and all the wildlife and birds you see on the way. Once you get out on the beach, they can help you identify all your amazing shelling finds. You are also welcome to swim and relax in the beautiful gentle Gulf water!
Rising Tide’s Life’s a Beach Shelling Cruise leave at 9am and 1pm (9am only in summer, May to October), and last three hours so you get the most time on Keewaydin to hunt for shells.
If you plan ahead, you can have a magical exclusive sunset experience of Keewaydin on Rising Tide’s Sunset to Full Moon Cruise! This three hour boat tour leaves in the afternoon (around 5 to 6 pm, depending on sunset), and is only offered a few days per month (October thru May) when the moon is full. Your biologist boat captain will give you a tour of Rookery Bay, swinging past the famous bird rookery island where hundreds of herons, egrets, ibis, and pelicans will be flying overhead to nest on the island for the night. Then you will head out to Keewaydin to do some shelling and watch the sun set over the Gulf, and the full moon rise over the island. Your boat ride back through the mangrove forest will be lit by the full moon and the beautiful star filled sky. A memorable trip from start to finish!
So what shells can I find?
The only left handed shell in Florida! Lightning whelks are predators that eat clams and other bivalves by drilling a hole into their shells. They also use the sharp strong edge of their shell to shuck open clams. Lightning whelks have beautiful brown and orange zig zag lightning bolt stripes, and can grow up to 16 inches, making it one of the larger shells you can find.
The state shell of Florida, and a fan favorite because they grow so huge- up to 26 inches! The horse conch is a fierce predator and can be found in the mud flats eating clams and other gastropods. The horse conch is very fun to find when it is alive because the body of the snail is bright orange.
Florida fighting conch
These shells are abundant on our SW Florida beaches and are usually in very good shape because they are thick, but can become weathered because it takes time for the shell to wash up to the tide line after the snail dies. The baby fighting conch shells are a slightly different shape than the adults, and shellers can confuse them for cone snails.
Kings crown conch
These snails live in the bays in oyster beds where they can feast all day on oysters, but their shells wash up on the beaches after they die. These shells are interesting for their spiraling row of spines that looks like a crown, which help camouflage them on the oyster reef.
These shells are one of the most beautiful and pleasingly shaped shells found on our beaches. Their color varies from red-orange, to pink, to a blue purple. The snails live in the bays and mudflats, but after they die their shells wash up on the beaches. They are beautiful when they are alive because the body of the snail is black with tiny white dots like the milky way galaxy.
A Florida Gulf Coast specialty shell! This shell is very thin and easily damaged, but can still be found on Gulf Coast beaches thanks to our gentle baby waves. Often mistaken for the pear whelk, but easily distinguished by how thin and delicate it is.
The alphabet cone and Florida cone are the most commonly found varieties of cone snail on our beaches. Different types of cone snail are found around the world, with famously deadly stinging varieties found in Australia. All cone snails are predators when they are alive, and hunt by ambushing fish by stinging them with a poisonous harpoon, so if you are lucky enough to find one alive be careful as you return it gently to the sea.
Often called the Sharks Eye for its mesmerizing blue colored iris mimicking spiral, in a matter of only ten minutes this predatory snail can drill a perfectly round hole into the shells of its prey, such as small clams or other snails- and they often eat several per day.
These shells are well known for their interesting spiny, frilly, and lacy ridges. The apple murex is the most common murex on our beaches, and they are usually a soft tan orange color. Many murex eat oysters, giving them the nick name the ‘oyster drill’. Most murex snails have a special purple gland that was used to make purple dye in Mediterranean cultures.
Very common on Florida beaches, these are actually a type of clam. The ponderous ark has a black mossy coating on the shell that wears off as the shell is tumbled in the surf. When arks are alive many species anchor themselves with thin strong spider-web like strands called byssus to rocks or corals. In the Gulf, many ponderous ark shells are found with false sea fans attached to them.
What they lack in size they make up for with abundance and incredible colors. Look for these little bivalves emerging and burying themselves at the shoreline where the waves wash up onto the shore and pull back out, especially in late summer. They filter feed for plankton as the gentle waves wash by, and move throughout the day to follow the tide line. Coquina are very sensitive to environmental changes, so large colonies of coquina are an indicator of healthy beach ecosystems.
These are one of the larger and most common bivalve shells you will find on the beach, easily recognizable by their orange exterior and pink interior. Cockles live buried in the sand and soft mud, extending their siphon into the water to breathe and filter feed. They often live close to shore, so the empty shells wash up in good condition.
The beautifully colored and highly variable calico scallop are one of everyone’s favorite shells to collect. They can be almost any color, including red, orange, yellow, purple, pink, white, black, and every combination of the above. Black and grey shells are colored by living buried in thick mud on the bottom where there is little oxygen. Did you know scallops can swim through the water by opening and closing their shells and pushing water through?
Sunray Venus clam
These pretty pink striped shells can be found on the beaches and mudflats of SW Florida, and can often be found with both halves still attached. Like the cockle, they live buried in the sand and soft mud, often in estuaries, where they filter feed and help clean the water. There is talk of making the sunray Venus clam a new aquaculture crop in Florida because of their similarity to conch meat.
These big white shells are very distinct because of their elongated wing shape. These bivalves live in the soft mud by digging a burrow that can be several feet deep and leaving an opening where they can stick out their filter feeding tongue.
Most often only the top half of this translucent pastel colored shell is found, the bottom remains in the ocean, stuck to whatever hard surface it was growing on- such as a rock or another shell. Jingle shells are filter feeders that help clean the water. Jingle shells are popular for making wind chimes because of the pleasing sound the shells make when they clink together.
One of the biggest bivalves that can be commonly found on the beach, these shells are very unique looking. They live in shallow water and are commonly found washed up after big storms. These dark iridescent shells are thin, yet spiny, and can often be found with the golden bundles of byssal threads still attached.
Worm (snail!!) shells
These fun spiraling bendy straw shells can be found in all different shapes on our beaches, and they actually once contained snails, not worms! They all start out tightly spiraled like a gastropod, but then elongate and spin out into different shapes as they grow.
When sand dollars are alive they are covered in a purple grey velvet. These spiny hairs are actually used as feet to move the sand dollar along the bottom and the bury themselves in the sand. When the sand dollar dies the hairs all fall off, leaving the white skeleton shell behind. The star pattern seen on the top of the shell are where the sand dollar breathed when it was alive. The large holes in the shell make is easier to bury themselves, by allowing sand to pass through, they also allow food that settles on top of the sand dollar to be passed through to the mouth on the bottom of the shell. The best time to see these shells alive is in later summer.
Similar to the sand dollar, the urchin shells you find on the beach are only the skeleton left behind. When urchins are alive they are covered in spines, and when the urchin dies and the spines fall off they leave behind little bumps on the round urchin shell. Urchins eat plants, so can be helpful in coral reefs where they prevent the reef from being overgrown with plants, but can be disastrous in kelp forests when they overgrow and destroy the whole forest.
All all of the photos used in this blog with black backgrounds are from the Bailey- Matthews National Shell Museum, located nearby on Sanibel Island. They have an incredible shell collection, including the world champion largest shells of many species, plus touch tanks, and beautiful aquariums. We highly recommend visiting the museum while you are in Florida.
Join Rising Tide Explorers on the Life’s a Beach Shelling Cruise on your next visit to Southwest Florida for the best possible shelling opportunity- miles of secluded Keewaydin beach all to yourself, guided by a biologist boat captain who can tell you all about your special shelling finds!