Operculum (fish)

The operculum is a series of bones found in bony fish and chimaeras that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding.

The preoperculum is a crescent-shaped structure that has a series of ridges directed posterodorsally to the organism’s canal pores.

The preoperculum can be located through an exposed condyle that is present immediately under its ventral margin; it also borders the operculum, suboperculum, and interoperculum posteriorly.

The suboperculum is rectangular in shape in most bony fish and is located ventral to the preoperculum and operculum components.

The thicker and more dense bone may have been favored due to selective pressures exerted from the threespine stickleback's environment.

The Endothelin1 pathway is thought to be associated with the development of the operculum bone since it regulates dorsal-ventral patterning of the hyomandibular region.