Campanologies hector is
1. percussion (gill cover), 2. lateral line, 3. dorsal fin, 4. adipose fin, 5. caudal peduncle, 6. caudal fin, 7. anal fin, 8. photophores, 9. pelvic fins (paired), 10. pectoral fins (paired)

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. These appear to be derived from the separate gill-slit covers of an elasmobranch ancestor of the teleost fishes. 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, the operculum is vital in obtaining oxygen. It opens 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.

Cartilaginous fishes do not have an operculum. Without an operculum, other methods of getting water to the gills are required, such as ventilation.

[edit] See also

• Hyomandibula

[edit] References

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

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