Definition of operculum in English:

Share this entry


Pronunciation: /ōˈpərkyələm/

noun (plural opercula /-lə/)

Zoology & Botany
1A structure that closes or covers an aperture, in particular.
Example sentences
  • In amphibians the inner ear is mechanically coupled to the pectoral girdle through the operculum.
  • Therefore, the operculum is always visible in complete specimens.
  • It is able to withdraw the whole of its body into its shell which is then sealed by an amber-coloured operculum.
1.1 technical term for gill cover.
Example sentences
  • In amphibians the inner ear is mechanically coupled to the pectoral girdle through the operculum.
  • On the bottom of their operculum or gill-cover, they have a sharp spine. Angelfish all vary in color and pattern.
  • Due to the close proximity of the operculum and the pectoral fins, water jetting out of the operculum could affect flow over the pectoral fins, possibly changing locomotory efficiency.
1.2A secreted plate that serves to close the aperture of a gastropod mollusk’s shell when the animal is retracted.
Example sentences
  • Above the head and the arms is a leathery, protective hood, that acts like an operculum to protect the animal when it withdraws inside its shell.
  • They inhabit salt marshes near the sea, and are able to seal the shell with the operculum and so survive dry periods buried in mud.
  • Many snails have an operculum, a horny plate that seals the opening when the snail's body is drawn into the shell.
1.3A lidlike structure of the spore-containing capsule of a moss.
Example sentences
  • As the spores grow, fluid pressure builds up in the ascus until the operculum bursts open and the ascospores are blown out into the environment.
  • The sporophytes also develop opercula, peristomes, continuous columella, and a spongy layer between the amphithecium and the spore mass.



Pronunciation: /-lər/
Example sentences
  • A key component of this relationship in rainbow trout was the timing of body velocity (aka ram movement) during opercular abduction which prevented backflow of water into the opercular cavity.
  • Moreover, since the opercular openings are quite small and the musculature responsible for abduction is not fully developed, fluid will tend to flow out of the mouth as the hyoid returns to its resting position.
  • We then determined phase differences between pectoral fin beating and opercular jetting (respiration).


Pronunciation: /-ˌlāt/
Example sentences
  • The Amphibolids are the only operculate pulmonates.
  • Consequently, Peziza and other forms have evolved asci which are operculate, meaning that they have a sort of lid on the end.


Early 18th century: from Latin, literally 'lid, covering', from operire 'to cover'.

For editors and proofreaders

Syllabification: o·per·cu·lum

Share this entry

What do you find interesting about this word or phrase?

Comments that don't adhere to our Community Guidelines may be moderated or removed.