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  • José H. Leal

Local Micro-lefties


A common misconception among Southwest Florida (and Florida in general) shell enthusiasts is that the iconic (and relatively common) Lightning Whelk, Sinistrofulgur sinistrum (Hollister, 1958), is the only local marine snail normally with a left-handed (sinistral) aperture (handedness in a snail is determined by looking at its shell with the apex pointing up.) Lightning Whelks are large, reaching in excess of 38 cm (about 15 inches.) However, when one takes into account small-size species (micromollusks), other examples of local sinistral-shelled snails come on the scene. The Modest Triphora, Marshallora modesta (C.B. Adams, 1850), thrives within sea sponges, where it finds shelter and food. The species is one of a few examples of triphorids occurring locally on Sanibel and Captiva. Another sinistral species that comes to mind is the Left-handed Melampus, Blauneria heteroclita (Montagu, 1808), a snail that lives under the bark of local red-mangrove trees, well above the water line. Melampus are members of a family of snails that evolved to live their lives on land, breathing air, only returning to seawater to lay their eggs within gelatinous masses. Read more about mollusks and their shells at our Shell Guide and Blog.

From left, the Modest Triphora, Marshallora modesta, and Left-handed Melampus, Blauneria heteroclita. One mm (millimeter) = 0.08 inch. Photos by José H. Leal and James F. Kelly.