operculumn.
/ə(ʊ)ˈpəːkjᵿləm/, /ɒˈpəːkjᵿləm/, U.S. /oʊˈpərkjəl(ə)m/ A structure forming or resembling a lid or cover.
I. Scientific uses.
1. Zoology.
a. The calcareous, horny, or fibrous plate secreted by some gastropod molluscs, esp. prosobranchs, which serves to close the aperture of the shell when the animal is retracted.
ΘΚΠ
the world > animals > invertebrates > subkingdom Metazoa > grade Triploblastica or Coelomata > phylum Mollusca > [noun] > mollusc or shell-fish > parts of mollusc
ungulaa1382
mantlea1475
trunk1661
diaphragm1665
lid1681
operculum1681
ear1688
beard1697
corslet1753
scar1793
opercle1808
pleura1826
pallium1834
byssus1835
cephalic ganglia1835–6
opercule1836
lingual ribbon1839
tube1839
cloak1842
test1842
collar1847
testa1847
rachis1851
uncinus1851
land-shell1853
mantle cavity1853
mesopodium1853
propodium1853
radula1853
malacology1854
gill comb1861
pallial cavity1862
tongue-tootha1877
mesopode1877
odontophore1877
pallial chamber1877
shell-gland1877
rasp1879
protopodium1880
ctenidium1883
osphradium1883
shell-sac1883
tooth-ribbon1883
megalaesthete1885
rachidian1900
scungille1953
tentacle-sheath-
the world > animals > invertebrates > phylum Arthropoda > class Crustacea > [noun] > subclass Entomostraca > order Cirripedia > member of > parts of > flap or lid of shell
operculum1681
opercle1808
opercule1836
1681 N. Grew Musæum Regalis Societatis 130 That little Shell called Blatta Byzantia, is the Operculum or Lid of the Purple.
1776 E. M. da Costa Elements Conchol. v. 121 The operculated Land Univalves are very different; they form a new lid or operculum every year.
1777 G. Forster Voy. round World I. 434 The round operculum, or cover of a shell.
1851 S. P. Woodward Man. Mollusca i. 47 Most spiral shells have an operculum, or lid, with which to close the aperture when they withdraw for shelter.
1866 J. G. Murphy Crit. Comm. Exodus xxx. 34 Onycha is probably the operculum..or lid of the shell of a strombus.
1903 Amer. Naturalist 37 518 At this stage [in the growth of young Fulgur] the operculum is already well developed.
1951 Ecology 32 75/2 Large Busycon, still affixed to quahogs.., also held the operculum wedged between the quahog valves.
1990 Jrnl. Zool. 220 149 Sinotaia quadrate remained uneaten as the crabs were unable to break the heavy viviparid shell or penetrate the horny operculum.
b. The bony flap covering the gills of a fish; a gill cover. Also: a fleshy flap that grows over the gills of a larval amphibian.In bony fishes the flap consists of four bones: the preopercular, interopercular, subopercular, and opercular bones. The term operculum is sometimes restricted to the latter of these, which is the hindmost and largest of the bones (cf. opercular n.).
ΘΚΠ
the world > animals > fish > parts of fish > [noun] > gill(s) or parts of
ginnle?c1475
gill vein1683
arista1691
radius1691
fish-ear1748
operculum1752
flap1803
opercle1808
subopercle1822
preoperculum1828
preopercule1842
preopercular1851
interoperculum1855
preoperclec1857
raker1903
1752 J. Hill Gen. Nat. Hist. III. 225 They are in great part covered by the opercula of the gills.
1849 H. D. Thoreau Week Concord & Merrimack Rivers 31 There is also another species of bream..without the red spot on the operculum.
1880 A. Günther Introd. Study of Fishes 38 The operculum, forming the posterior margin of the gill-opening.
1923 Proc. Royal Soc. B. 94 205 Anuran tadpoles, transitorily, possess external gills, but for the greater part of their aquatic life the pharyngeal clefts are protected by a well-developed operculum.
1960 D. C. Braungart & R. Buddeke Introd. Animal Biol. (ed. 5) xvii. 248 The organs of respiration are the four pairs of gills borne by the first four pairs of gill arches and protected by the opercula.
1992 Pract. Fishkeeping (BNC) Nov. 84 An orange stripe runs from the eye, across the operculum, ending at the base of the pectoral fin.
2. Zoology. Any of various other structures covering or closing an aperture; spec. (a) a small bone in the middle ear of amphibians or (formerly) in the inner ear of birds; (b) either of the two upper movable plates of the shell of a barnacle, covering the mantle cavity; (c) each of one or more plates or scales covering various organs, spiracles, etc., in arthropods; (d) the lid of the polyp in certain bryozoans, which closes when the zooid is withdrawn; (e) a flap or scale that covers the ear or nostril in certain birds and mammals; esp. a feathered flap covering the ear of an owl; (f) a cap on the egg of an insect or parasitic worm, which opens when the larva hatches; (g) a modified prostomial palp in tube worms, forming a stalked knob that closes the tube when the worm withdraws into it.
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the world > animals > birds > order Strigiformes or owl > [noun] > parts of
operculum1713
disc1769
ear tab1851
plumicorn1883
the world > animals > invertebrates > phylum Arthropoda > class Insecta > parts of insects > [noun] > thorax > metathorax > covering of spiracles on
operculum1816
the world > animals > invertebrates > subkingdom Metazoa > grade Triploblastica or Coelomata > phylum Polyzoa > [noun] > class Ectoprocta > order Gymnolaemata > suborder Chilostomata > member of > movable lid of cell
operculum1840
the world > animals > invertebrates > subkingdom Metazoa > grade Triploblastica or Coelomata > phylum Polyzoa > [noun] > class Ectoprocta > order Gymnolaemata > suborder Ctenostomata > movable lid of cell
operculum1888
1713 W. Derham Physico-theol. vii. ii. 382 This Bottom, or Base of the Columella [in the inner ear of a bird], I call the Operculum.
1777 T. Pennant Brit. Zool. (ed. 4, quarto) IV. vi. 72 Lepas..Common English Barnacle..the lid or operculum sharp pointed.
1816 W. Kirby & W. Spence Introd. Entomol. (1818) II. xxiv. 405 The drum-covers or opercula [of the cicada] from beneath which the sound issues.
1840 Penny Cycl. XVIII. 366/1 Myriapora. Animals cylindrical, terminating anteriorly in a tubular extensible proboscis..; on one side of this body is a cartilaginous round operculum.
1842 Penny Cycl. XXIII. 117/2 The aperture of the ear..is large, measuring,..in the Brown Owl, more than an inch in length. This is protected by an operculum.
1888 G. Rolleston & W. H. Jackson Forms Animal Life (ed. 2) 523 Limulus has six pairs of limbs on the abdominal mesosoma, of which the first pair fuse to form a genital operculum.
1897 T. C. Allbutt et al. Syst. Med. II. 1017 The shell [of the egg of Bothriocephalus latus] is simple, brown, and closed in at one end with an operculum.
1909 B. F. Kingsbury & H. D. Reed in Science 30 Apr. 716/1 The second element [in the ear of tailed amphibia], which we designate as the operculum, has no skeletal connections.
a1933 J. A. Thomson Biol. for Everyman (1934) I. viii. 158 Spirorbis..has branched gill-threads which can be protruded at the mouth of the tube, and one of these has been transformed into a stopper (or operculum) which shuts the tube when the worm draws itself in.
1959 J. Van Tyne & A. J. Berger Fund. Ornithol. ii. 40 A further modification is a protective operculum (cover) over the nostril, as in Galliformes and some passerines.
1969 R. F. Chapmen Insects xvii. 337 The eggs of some species have a cap, or operculum.
1986 G. Culverwell tr. P. Arduini & G. Teruzzi Macdonald Encycl. Fossils No. 26 The corallite is semicircular and the calyx is closed by an operculum.
1989 Encycl. Brit. XIII. 917/1 His maneuvers also serve to bring the spermatophore near the open genital opercula of the female [scorpion].
1994 E. E. Ruppert & R. D. Barnes Invertebr. Zool. (ed. 6) xi. 550/1 Some species of Spirorbis brood their eggs in the cavity of the operculum.
3. Botany.
a. The lid of the capsule in mosses.
ΘΚΠ
the world > plants > particular plants > moss > [noun] > parts of
moutha1398
fimbria1752
calyptra1753
veil1760
lid1776
apophysis1785
operculum1788
peristoma1792
peristome1799
peristomium1806
hair-point1818
vaginula1818
perigynium1821
vaginule1821
gemma1830
paraphyllium1832
tympanum1832
perigon1857
pseudopodium1861
commissure1863
ocrea1863
cap1864
chaeta1866
struma1866
membranulet1891
pyxis1900
pseudopod1914
annulus-
1788 J. Lee Introd. Bot. (ed. 4) Gloss. 422 Operculum, a Cover, as in the Mosses.
1840 Penny Cycl. XVI. 9/2 The urn itself [of mosses] is closed by a lid, or operculum.
1858 J. Hogg Microscope (ed. 3) ii. i. 207 These spore-capsules are closed on their summit by opercula or lids.
1904 Bull. Torrey Bot. Club 31 321 The operculum of the present plant is in the dry state apiculate or mucronate.
1954 Amer. Midland Naturalist 52 3 Wardia Harv. Alar cells numerous, enlarged, transparent. Operculum attached to columella.
1998 L. Margulis & K. V. Schwartz Five Kingdoms (ed. 3) v. 384/2 In mosses of the class Bryopsida, tissue beneath the operculum splits into a circlet of teeth called the peristome.
b. Any of various covering structures in higher plants; spec. (a) a structure which covers the unopened flower in eucalypts, composed of fused sepals, petals, or bracts; (b) the lid of the pitcher of a pitcher plant; (c) a cap or lid on a capsule, fruit, or seed, frequently dehiscent; (d) a lid-like structure on the surface of some pollen grains.
ΚΠ
1830 J. Lindley Introd. Nat. Syst. Bot. 64 In Eucalyptus..the sepals are consolidated into a cup-like lid, called the operculum.
1840 Penny Cycl. XVI. 446/1 Operculum... This term..has also been applied to the lid which covers in the Pitcher of Nepenthes, where it is the lobe of a modified leaf.
1887 Bull. Torrey Bot. Club 14 158 Echinopepon. Annual;..fruit oblong, attenuate at both ends, dehiscing at the apex by a deciduous operculum.
1911 New Phytologist 10 324 Pollen granulate with smooth operculum, larger than in alba.
1954 Amer. Jrnl. Bot. 41 41/2 The hypocotyl emerged from the seed through a hole left by the operculum, which was formed by a circular abscission layer in the seed coat.
1976 P. Bell & D. Coombe tr. Strasburger's Textbk. Bot. (new ed.) 650 The diversity of forms [of pollen grains] from simple to complex is enhanced by differentiation of the pore margin.., the formation of lid-like opercula, [etc.].
2001 Nuytsia 13 487 The new species differs from E[ucalyptus] orbifolia in the smaller buds with a short hemispherical operculum.
c. The cap of the ascus in certain cup fungi. Also: a cap on the sporangium in fungi of the order Chytridiales.
ΘΚΠ
the world > plants > particular plants > fungi > [noun] > parts of > reproductive parts
capsule1693
perithecium1800
aecidium1821
hymenium1830
pseudoperidium1832
pseudoperithecium1832
disc1842
trichidium1842
spicule1843
sporophore1849
stylospore1851
pycnide1856
cyst1857
pycnidium1857
basidium1858
cystidium1858
basidiospore1859
conidium1861
pollinarium1861
gonosphere1865
hymenophorum1866
spicula1866
teleutospore1866
promycelium1867
gonosphaerium1873
hymenophore1874
paracyst1874
sterigma1874
pollinodium1875
scolecite1875
uredospore1875
metuloid1879
operculum1879
uredo1879
aecidiospore1880
pycnidiospore1880
uredo-fruit1882
chlamydospore1884
teleutosorus1884
fruitcake1885
ascocarp1887
periplasm1887
pycnospore1887
pyrenocarp1887
macrostylospore1894
autobasidium1895
oidium1895
zygophore1904
aeciospore1905
aecium1905
pycniospore1905
teliospore1905
telium1905
uredinium1905
uredosorus1905
fruit-body1912
sporodochium1913
probasidium1916
fruiting body1918
pycnium1926
holobasidium1928
protoperithecium1937
uredium1937
1879 W. Phillips tr. E. Boudier in Grevillea 8 46 I..call the attention of mycologists to the necessity of separating this family [sc. of Discomycetes] into two very natural sections, according as to whether the mode of dehiscence is with or without an operculum.
1887 E. Haeckel in Rep. Sci. Results Voy. H.M.S. Challenger: Zool. XVIII. i. p. iv This osculum is closed by a radiate cover (astropyle or operculum radiatum).
1906 Bot. Gaz. 42 467 This pore is at first covered by a small cap or operculum, bounded by a thickened ring in the wall of the ascus where the cover breaks off.
1945 Q. Rev. Biol. 20 385/2 Figure 17..of a polycentric chytrid, Nowakowskiella, is here shorn of one sporangium and is devoid of an operculum.
1991 Bot. Gaz. 152 419/1 Trappe..emended the Pezizaceae to include..cylindric to saccate asci lacking a functional operculum.
4. Anatomy. The area of the cerebral cortex that covers the insula; each of the smaller areas that constitute this, separated by rami.
ΘΚΠ
the world > life > the body > nervous system > cerebrospinal axis > brain > parts of brain > [noun] > cortex > parts of
molecular layer1867
motor cortex1880
Wernicke's area1887
operculum1889
map1945
1889 A. H. Buck Ref. Handbk. Med. Sci. VIII. 160/2 The insula..becomes a subgyre, while the operculum, preoperculum, suboperculum, and postoperculum are supergyres.
1909 Philos. Trans. (Royal Soc.) B. 200 121 Ramus horizontalis anterior.—This..is a short cleft separating the frontal operculum from the orbital lobe.
1967 Brain 90 198 Börnstein (1922) put forward the view, widely accepted today, that the primary cortical centre for taste is in the parietal operculum.
1989 Brain 112 960 CT demonstrated an infarct in the frontal operculum without striatal involvement.
II. General uses.
5. In general use: a cover. Also figurative.
ΘΚΠ
the world > space > relative position > condition of being external > covering > [noun] > a covering
wrielsc825
coverc1320
hillingc1325
eyelida1382
covering1382
casea1398
coverta1400
tegumentc1440
hacklea1450
coverturec1450
housingc1450
deck1466
heeler1495
housera1522
coverlet1551
shrouda1561
kever1570
vele1580
periwig1589
hap1593
opercle1598
integument?1611
blanketa1616
cask1646
operiment1650
coverlid1654
tegment1656
shell?1677
muff1687
operculum1738
tegmen1807
1738 T. Shaw Trav. Barbary & Levant iv. v. 425 The Head of Isis..for the Operculum.
1837 Civil Engineer & Architect's Jrnl. 1 58/1 They carry small square bits of black paper, which project in front of the screen, and serve as opercula or covers to conceal the letters.
1866 R. D. Blackmore Cradock Nowell (1883) xxiv. 116 Noble wine deserves not to be the mere operculum to a stupidly-mixed hot meal.
1958 H. Nemerov Mirrors & Windows 75 Horny, let thy drawn Operculum defend thee now.
1979 Time 8 Jan. 59/3 The fact is emphasized by the tip of the building—the now famous ‘grandfather clock’ pediment with its round operculum, through which the heating system will issue clouds of steam on cold days.
This entry has been updated (OED Third Edition, June 2004; most recently modified version published online June 2022).
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n.1681