operculum

views updated May 08 2018

operculum
1. In animals, a lid or cover, sometimes hinged, occurring, for example, in some cylindrical rugose corals, some bryozoans, and in gastropods.

2. A flap of skin covering the gills in bony fish (Osteichthyes).

A Dictionary of Earth Sciences AILSA ALLABY and MICHAEL ALLABY

operculum

views updated May 23 2018

operculum A little lid. In plants, the term usually refers to the dehiscent cap present on certain moss capsules or other types of sporangia.

A Dictionary of Plant Sciences MICHAEL ALLABY

operculum

views updated May 14 2018

operculum
1. (in zoology) A lid or flap of skin covering an aperture, such as the gill slit cover of fish and larval amphibians and the horny calcareous operculum secreted by many gastropod molluscs, which closes the opening of the shell when the animal is inside.

2. (in botany) The cone-shaped lid of the capsule of mosses, which is forcibly detached to release the spores.

A Dictionary of Biology

operculum

views updated May 18 2018

operculum (pl. opercula) A little lid or cover. In Prosobranchia, a rounded, horny or calcareous plate, carried on the foot, that closes the aperture when the animal withdraws into its shell. See also GILL COVER.

A Dictionary of Zoology MICHAEL ALLABY

operculum

views updated May 23 2018

operculum (oh-per-kew-lŭm) n. (pl. opercula) a plug of mucus that blocks the cervical canal of the uterus in a pregnant woman. When the cervix begins to dilate at the start of labour, the operculum, slightly stained with blood, comes away as a discharge (‘show’).

A Dictionary of Nursing