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n. pl. o·per·cu·la (-lə) or o·per·cu·lums
Biology A lidlike structure covering an opening, especially:
a. A bony plate that covers and protects the gills of most bony fishes. Also called gill cover.
b. A horny or calcareous plate attached to the foot of most larval and many adult gastropods, used to close the aperture when the animal retracts into its shell.
c. A covering at the top of the spore capsule of most mosses, falling off when mature spores are released.

[Latin, lid, from operīre, to cover; see wer- in Indo-European roots.]

o·per′cu·lar (-lər) adj.
References in periodicals archive ?
Neurogenesis suggests independent evolution of opercula in serpulid polychaetes.
Development of lava slowly and gradually started to move its jaws, pectoral ns and opercula aps.
The posterior disconnection takes place after fully opening the Sylvian fissure and promptly elevating the parietal opercula (28,50).
Abstract--Aging of tautog (Tautoga onitis) has historically required sacrificing fish to obtain opercula and otoliths.
The combination group showed significant increases in metabolism in a number of regions, including the right hemisphere cluster (insula/putamen/ amygdala/superior and middle temporal region); the left middle temporal pole fusiform gyrus and anterior temporal region; the right middle and inferior frontal region; and the right rolandic opercula.
1983; Nakamura and Parin, 1993): body fairly elongate and strongly compressed; lower jaw beyond tip of upper jaw; vomer edentate; gill rakers degenerated; a single fairly straight lateral line, from above upper angle of opercula, gradually sloping posteriorly and running straight from mid first dorsal fin to caudal fin base.
4 SELECTED EXAMPLES OF SINGULAR AND PLURAL FORMS Singular/Plural Example a/ae gingiva, gingivae ex/ices index, indices i/us alveoli, alveolus is/es diagnosis, diagnoses on/a ganglion, ganglia um/a operculum, opercula BOX 1.
The opercula in both sexes bear small and irregularly arranged spots (Esmaeili et al.
The locations in which the gill lice attached to the host fish varied, but the majority were found attached to gills, branchial rims, and opercula.
For each specimen were examined the mouth, opercula, gills and gastrointestinal tract to parasites collection (protists and metazoans).
We collect over 100,000 samples from over 30 important Northeast fisheries species every year," said Robillard: scales, otoliths (ear stones), stomachs, spines, and opercula (bony flaps that protect gills) offish, as well as shells of clams and scallops.