The Cloudy Periwinkle, Littoraria nebulosa (Lamarck, 1822), is found along the coast of Southwest Florida, living above the high tide line, mostly on dead tree trunks and branches. Periwinkles are marine gastropods that became almost completely independent of the aquatic environment. They feed on microalgae and fungi that grow on hard surfaces above the high tide line. Females return to seawater to lay egg their egg capsules, but, other than that, they spend their entire lives in the terrestrial environment. Three species of periwinkles inhabit the coast of Southwest Florida. Locally, the Cloudy Periwinkle lives mostly on dead trees, old wood docks, and other inert wood structures . The Mangrove Periwinkle, Littoraria angulifera (Lamarck, 1822), is found on the trunk and branches of Red Mangrove trees, Rhizophora mangle, and the Placid Periwinkle, Echinolittorina placida Reid, 2009, prefers rocks and man-made concrete structures. I shot the photo below a couple of years ago at Cayo Costa State Park. The image shows unusually bluish-colored Cloudy Periwinkles nestled in a hollow in a dead Black Mangrove tree, Avicennia germinans. Read more about local mollusks in the Southwest Florida Shell Guide.
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