Operculum (fish) 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 suboperculum is rectangular in
Velvet belly lanternshark well-separated from one another. The coloration is brown above, abruptly transitioning to black below. There are thin black marks above and behind the pelvic fins, and along the caudal fin. The velvet belly possesses numerous photophores that emit a blue-green light visible from away. Varying densities of photophores are arranged in nine patches on the shark's sides and belly, creating a pattern unique to this species: photophores are present along the lateral line, scattered beneath the head but excluding the mouth, evenly on the belly, and concentrated around the pectoral fins and beneath the caudal peduncle. The maximum reported length