Operculum (fish) required, such as ventilation.. Operculum (fish) The operculum is a series of bones found in bony fish that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding. The opercular series contains four bone segments known as the preoperculum, suboperculum, interoperculum and operculum. The preoperculum is a crescent-shaped structure that has a series of ridges directed posterodorsally to the organisms 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
Apogonichthyoides pharaonis ridge and saw-like margin. There is a spine which projects from the operculum in line with the central point of the eye. There are three vertical black bars which contrast with the grey-brown ground colour of the body, there is one bar running down from each dorsal fin and the last bar is on the caudal peduncle. There is a characteristic black ‘eye-spot’ surrounded by a yellow ring within the first bar. The first dorsal fin has a dark leading edge while that of the pelvic fins is white. "Apogonichthyoides pharaonis" is native to the western Indian Ocean from the