Anatomy
O
Operculum
/ /ɒˈpɜːkjʊləm/ /
Etymology:
From Latin operculum — "lid, cover"
Quick Definition
The bony gill cover in bony fishes, consisting of four bones that protect and seal the gill chamber.
📖 Full Definition
The operculum is the bony flap that covers and protects the gills in teleost fishes. It is composed of four bones: the opercle, preopercle, interopercle, and subopercle. Its opening and closing, coordinated with the buccal cavity, drives the unidirectional flow of water over the gills. In primitive fishes (sharks, rays) there is no bony operculum — the gill slits are exposed directly. The size, shape and spine ornamentation of the opercle are important taxonomic characters.
💡 Examples & Context
The opercle of the European perch (Perca fluviatilis) bears a characteristic sharp spine.