Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
The operculum is a protective structure that covers the opening of a mollusc's shell when the animal retracts inside. It acts as a barrier against predators and environmental stress.
5 Must Know Facts For Your Next Test
The operculum is commonly found in gastropods like snails.
It is often composed of calcium carbonate or proteinaceous material.
Opercula can vary in shape and size depending on the species.
In some annelids, an operculum can also be present to protect their tube-like structures.
The operculum helps prevent desiccation in terrestrial molluscs.
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Related terms
Mantle: A significant part of a mollusc's anatomy that secretes the shell and forms a cavity for respiration and excretion.
Radula: A toothed, chitinous ribbon used by molluscs for feeding, often compared to a tongue.
Setae: Bristle-like structures in annelids used for locomotion or sensory purposes.