Operculum (fish)

Bones of the operculum: Opercule (yellow), Preopercle (red), Interopercle (green) and Subopercle (pink)

The operculum of a bony fish is the hard bony flap covering and protecting the gills. In most fish, the rear edge of the operculum roughly marks the division between the head and the body.

The operculum is composed of four fused bones; the opercle, preopercle, interopercle, and subopercle. The posterior rim of the operculum is equipped with a flexible, ribbed structure which acts as a seal to prevent reverse water flow during respiration. The morphology of this anatomical feature varies greatly between species. For example, the bluegill (Lepomis macrochirus) has a posteriorly and dorsally oriented rounded extension with a small black splotch present. In some species, the operculum can push water from the buccal cavity through the gills.

For some fish, opercula are vital in obtaining oxygen. They open as the mouth closes, causing the pressure inside the fish to drop. Water then flows towards the lower pressure across the fish's gill lamellae, allowing some oxygen to be absorbed from the water.

Whereas the cartilaginous ratfishes have soft and flexible opercular flaps, the sharks, rays and relatives (elasmobranch fishes) lack opercula completely and respire instead through a series of gill slits perforating the body wall. Without opercula, other methods of getting water to the gills are required, such as ventilation.

See also

• Fish
• Hyomandibula

References

• Fish, operculum (Gross, Low)
• BiologyBase, Fish Anatomy

Fish About fish Diversity Ethnoichthyology Evolution Diseases and parasites Fisheries Fishing Fish as food Fear of fish FishBase Fish kill Hypoxia in fish Ichthyology Anatomy and physiology Fish anatomy Fish physiology Estimating age Anguilliformity Bone dermal intramembranous ossification Cleithrum Chromatophore Fins dorsal fin Gill branchial arch gill raker gill slit pharyngeal arch pharyngeal slit Glossohyal Jaw hyomandibula pharyngeal jaw Leydig's organ Mauthner cell Meristics Operculum papillare Papilla Photophore Pseudobranch Root effect Shark cartilage Scales ganoine Spiral valve Suckermouth Swim bladder physoclisti physostome Teeth pharyngeal teeth shark teeth Teleost leptins Digital Library Sensory systems Sensory systems in fish Ampullae of Lorenzini Barbel Hydrodynamic reception Electrocommunication Electroreception Jamming avoidance response Lateral line Otolith Passive electrolocation Capacity for pain Schreckstoff Surface wave detection Vision Weberian apparatus Reproduction Fish reproduction Bubble nest Clasper Egg case Fish development Ichthyoplankton Juvenile fish Life history theory Milt Mouthbrooder Polyandry in fish Pregnancy Roe Sequential hermaphroditism Spawning triggers Locomotion Fish locomotion Fin and flipper locomotion Amphibious fish Walking fish Flying fish Undulatory locomotion Tradeoffs for locomotion in air and water RoboTuna Other behaviour Aquatic predation Aquatic respiration Bait ball Bottom feeders Cleaner fish Diel vertical migration Electric fish Filter feeders Forage fish Migrating fish Paedophagy Predatory fish Salmon run Sardine run Scale eaters Schooling fish Sleep in fish Venomous fish Fish intelligence Habitats Coastal fish Coldwater fish Coral reef fish Deep sea fish Demersal fish Euryhaline fish Freshwater fish Groundfish Marine habitats Pelagic fish Tropical fish Wild fish Other types Bait Coarse Diversity Farmed Game Genetically modified Hallucinogenic Oily Rough Whitefish Commercial fish Farmed fish Carp Salmonids Tilapia Wild fish Predatory fish billfish mackerel salmon tuna Forage fish anchovy herring sardine sprats Demersal fish cod flatfish pollock Major groups Jawless fish hagfish lampreys Cartilaginous fish chimaeras sharks rays Bony fish spiny-finned fleshy-finned Lists Aquarium fish Blind fish Fish common names Fish families Fish on stamps Ichthyology terms Large fish Threatened rays sharks Prehistoric fish more lists... Category Portal WikiProject