1. Plural of operculum; bony or membranous flaps covering the gills of fish.
Usage: biology; ichthyology
2. In botany and zoology, small lid-like structures that cover or close an opening in an organism.
Usage: biology; technical

Examples

• The fish's opercules flared open as it took in water through its mouth.
• Scientists examined the opercules of the salmon to study its respiratory system.
• The opercules protect the delicate gill filaments from damage.
• Different fish species have opercules of varying shapes and sizes.
• When the fish closes its opercules, water is forced over the gills.