Gastropods

Gastropods are a large and diverse class of Mollusca that includes snails and slugs. They inhabit marine, freshwater, and terrestrial environments worldwide, from ocean depths to forest floors. With tens of thousands of described species, gastropods are among the most speciose animal groups.

Anatomy: Most have a single shell (though it may be reduced or absent in slugs) and a broad, muscular foot for locomotion. A head bears eyes and tentacles, and a radula—a flexible ribbon of teeth—serves as a feeding organ. During larval development, many gastropods undergo torsion, twisting the body so the mantle cavity sits above the head; some lineages later modify or reverse this arrangement.

Shell diversity and forms: Snails retain prominent shells; limpets and abalones have cap-like shells; many slugs lack a shell. The life form ranges from coiled, spiral shells to flattened or shell-less bodies, and many species show vivid patterns and colors.

Ecology and reproduction: Gastropods occupy varied ecological roles as grazers, detritivores, and predators (for example, cone snails). Reproduction is diverse; many land snails are hermaphroditic, while aquatic species have separate sexes. Eggs are often laid in gelatinous clutches; some species give birth to live young or exhibit direct development.

Fossil record and importance: Gastropods have an extensive fossil record, largely due to their shells. They play key roles in ecosystems as herbivores and prey, and some species are economically significant as food or as pests.