Noun
The lid of a pitcherform leaf.
The lid of the urnlike capsule of mosses.
Any lidlike or operculiform process or part; as, the opercula of a dental follicle.
The fold of integument, usually supported by bony plates, which protects the gills of most fishes and some amphibians; the gill cover; the gill lid.
The principal opercular bone in the upper and posterior part of the gill cover.
The lid closing the aperture of various species of shells, as the common whelk. See Illust. of Gastropoda.
Any lid-shaped structure closing the aperture of a tube or shell.
Source: Webster's dictionaryA flap (operculum) opens and its stinging apparatus fires the barb into the prey. Source: Internet
In some species the retracted invert and lophophore are protected by an operculum ("lid"), which is closed by muscles and opened by fluid pressure. Source: Internet
The operculum can be important in adjusting the pressure of water inside of the pharynx to allow proper ventilation of the gills, so bony fish do not have to rely on ram ventilation (and hence near constant motion) to breathe. Source: Internet
Though all but the most primitive bony fish lack spiracles, the pseudobranch associated with them often remains, being located at the base of the operculum. Source: Internet
In both types the modified operculum is opened by other muscles that attach to it, or by internal muscles that raise the fluid pressure by pulling on a flexible membrane. Source: Internet
In many amphibians, there is also a second auditory ossicle, the operculum (not to be confused with the structure of the same name in fishes). Source: Internet