A Gastropod is a snail, having one shell, a large muscular foot, and a well-developed head with distinct eyes, mouth, and tentacles. Gastropods possess an operculum, a thin piece of shell attached to the foot and used to close the aperture (opening) when the animal retracts into its shell. They also have a radula, a tongue-like, toothed appendage used to saw, bore, tear, or scrape, depending upon how the species feeds. The first section below covers the gastropods very commonly seen on Hilton Head, and ones that I will always discuss in my beach programs. Those following the video are present, but not as commonly found.
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- Marsh Mud Snail
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- The Marsh Mud Snail is found in huge numbers on the tidal mud flats they call home. To avoid drying out at low tide they may congregate in tidal pools or burrow into the mud. They usually dine on microscopic plant life found in the mud, but if given the chance, will eat decaying animal matter. Swarms of mud snails will quickly gather to eat a dead fish on the tidal flat.
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- Marsh Periwinkle Snail escaping high tide on the Spartina Grass. The only habitat of the Marsh Perisinkle is the marsh because it is dependent on the brackish water, feeding on the algae on the surface of the marsh grasses.
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- A favorite of the Blue Crab, the Marsh Paeriwinkle is also eaten by shorebirds. These snails are a smaller cousin of the snail eaten as Escargot.
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- A large Lightning Whelk almost fully retracted behind its operculum.
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- A smaller Channeled Whelk.
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- Knobbed Whelk
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- Channeled Whelk
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- Channeled Whelk (top), Lightning Whelk (bottom left), and Knobbed Whelk (bottom right). Can you tell the difference.
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- Whelk egg case and the shells of unhatched baby whelks.
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- Pear Whelk
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- Pear Whelk
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- Moonsanil, aka Shark Eye, coming out for a visit. They move by extending their large foot forward and then pulling the shell forward.
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- The goldern operculum of a live Moonsnail.
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- Here you can see the coloration and dark whorls that gives this Moonsnail the name Shark Eye.
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- The foot is not yet fully retracted into the shell.
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- Moon Snail egg case found washed up on the beach in January. Also called a “collar,” these cases are made of sand particles glue together with a gelatinous material and do not survive keeping. If you find one, make sure you get a picture.
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- The Shark Eye is a voracious predator, having more in common with sharks than looking like an eye. They attack other mollusks by drilling a hole through the shell with their tooth covered and acid secreting radula (tongue). Once they have drilled the hole, which may only take a few minutes, they dissolve and suck out the flesh. Clams are preferred, but they will consume smaller Moonsnails too.
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- The trail of a Lettered Olive moving under the surface of he sand. They are among the fastest burrowers among gastropods. Olives live in the sandy bottoms from the low tide line to about 50 feet.
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- The Lettered Olive is the South Carolina State Shell. It is so namned because the markings are said to resemble writing.
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- They dine on clams, muscles, and cockles, pulling the shells open with their strong foot.
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- Banded Tulip Snails. Fairly common in the Carolinas, the Banded Tulip can reach 4 ½ inches in length with 7 distinct brown lines on its main whorl. The less common True Tulip is a much larger snail, reaching up to 10 inches in length, with 15 faint brown lines on its main whorl. Tulips prey on other mollusks, including other Tulips, by boring a hole through the shell.
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- Oyster Drills. Aptly named, the Oyster Drill is a ferocious predator on young oysters, drilling into the shell with its radula to consume the soft body. Oyster Drills cannot tolerate lower salinity waters, so marshes offer a safer habitat for oysters than more saline environments such as Port Royal Sound. This is a small snail reaching no more than 2 inches in length.
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- Auger Shell. Long and narrow, Augers can reach 2 inches in length. The Auger wats worms by engulfing them in its proboscis, a tube-like part of its mouth.
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- Horse Conch shell inhabited by a Hermit Crab.
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- Slipper Snails are one of the few marine snails that do not form a spiral shaped shell. The shelf supports and protects the animal. The Slipper Snail is hermaphroditic, starting life as male, but becoming female as the age and grow larger. They often live in stacks, with one large female anchoring a group of smaller males.
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- Baby Ears. The shell is slightly coiled, with the appearance from underneath giving the shell its name. When alive, the mantle and foot completely cover the shell and there is no operculum (I’d like to find this one alive). Like the Slipper Snail, the Baby’s Ear will sometimes attache itself to other creatures, like Horseshoe Crabs.
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- This Horseshoe Crab has some tag-alongs. In the upper left you can see a cluster of Baby’s Ears, while the larger creatures below are Slipper Snails.
