Mollusks

Leal Wentletrap

Leal Wentletrap, Epitonium leali García, 2011, is one of about eight species of Wentletraps (family Epitoniidae) that may be found on the beaches of Sanibel and Captiva. The species may be separated by other Wentletraps by the sculpture irregularly sized shell ribs (most ribs are thin, but some may be three or four times as thick as the thin ones), and microscopic spiral lines between the ribs. The uncommon species, which occurs in Florida and the Gulf of Mexico, was named after yours truly by D

The Atlantic Morum

The Atlantic Morum, Morum oniscus (Linnaeus, 1767) has a very characteristic, thick and heavy (for its size) shell with a sculpture of three spiral "rows" of squarish knobs. Its color is whitish or light gray with brown patches. Some shells retain its softer outer, or periostracum, which is dark-gray, velvety. Morum snails were included in the Helmet shell family Cassidae until 1987, when malacologists Hughes and Emerson demonstrated that it belongs within the harp shell family Harpidae. The Atl

The Giant Bittersweet

The Giant Bittersweet, Glycymeris americana (DeFrance, 1826), is the largest species of the Bittersweet family Glycymerididae found in the western Atlantic Ocean, attaining up to 5 inches in size. Shells of the species may be found along the beaches of Sanibel and Captiva after storms. Bittersweets feature a shell hinge that consist of a curved row of a large number of chevron-shaped “teeth” (top of left-hand photo). The hinge teeth in bivalves ensure that the two shell parts, or valves, do not

The Beautiful Semele

The Beautiful Semele, Semele bellastriata (Conrad, 1837), is truly one of the prettiest clams found in our barrier islands. Its shell is never longer than about one inch, and displays a sculpture of concentric ridges and radial ribs that combine to give a “criss-crossed” aspect to the shell surface. The Beautiful Semele is one (and the most attractive) of five species of the family Semelidae occurring in the area. What is remarkable about the Beautiful Semele is its variable coloration, with a b

The Cloudy Periwinkle

The Cloudy Periwinkle, Littoraria nebulosa (Lamarck, 1822), can be found along the coast of Southwest Florida living high above the high tide line on hard surfaces, mostly on dead tree trunks and branches. Periwinkles are marine gastropods that became almost completely independent of the aquatic environment. I took the photo on the right last weekend at Cayo Costa State Park during one of Captiva Cruises trips to the island. The image shows groups of unusually bluish-colored cloudy periwinkles

The Florida Caecum

These two pictures show the same shell, the Florida Caecum, Caecum floridanum Stimpson, 1851, a tiny gastropod not uncommon on the sandy beaches of SW Florida and that measures no more than 4 mm (a little beyond 1/8 inch). The genus name Caecum means “blind” in Latin, and the word is also used for any structure that ends in a blind tube or pouch. The photo on top was taken under a standard microscope, and the one on the bottom with a scanning electron microscope (SEM), a sophisticated piece of e

The Giant Triton

The Giant Triton, Monoplex parthenopeus (Salis Marschlins, 1793), may be occasionally found on the local beaches. It is a large gastropod that may reach 6 inches in size. The Giant Triton, which has an extremely bristly, “hairy” periostracum (the outer shell layer of mollusks), should not be confused with the Hairy Triton, which is a smaller species that does not occur on the barrier islands of SW Florida. The Giant Triton has very broad distribution in the tropical and subtropical regions of th

The Smooth Duck Clam

The Smooth Duck Clam, Anatina anatina (Spengler, 1802), is a bivalve rarely found in Southwest Florida. It is a close relative of the more common Channeled Duck Clam, Raeta plicatella (Lamarck, 1818), with which it could be confused. Both have very thin, fragile shells, but the latter species, however, shows a sculpture of broader concentric ribs and more rounded outline. The Smooth Duck Clam, as other species of the family Mactridae, has its two long siphons (one sucks water in for filter-feedi

The Dark False Mussel

A brackish water bivalve mollusk native to the Gulf of Mexico, the Dark False Mussel, Mytilopsis leucophaeata Conrad, 1831 has been introduced to the mid-Atlantic American states, Europe, and south to northeastern Brazil, possibly via ballast water in ships or among living Oysters. Dark False Mussels have non-descript, light-colored shells that may grow to about ¾ inch. They may be found locally on Sanibel in brackish water ponds and in the canals at the eastern end of the island. The Mussels, w

The Florida Lyonsia

The Florida Lyonsia, Lyonsia floridana Conrad, 1849, is a relatively common bivalve in the estuaries of Southwest Florida, in particular in areas with dense, compact mud. The half-inch shell is very thin, fragile and translucent. The young attach themselves to broken shells or small pebbles, by a very slender bundle of fibers called byssus. Unlike what happens to sturdier clam shells, the delicate nature of the Florida Lyonsia renders preservation of its shell difficult after the death of the an