micromeren.
/ˈmʌɪkrə(ʊ)mɪə/, U.S. /ˈmaɪkroʊˌmɪ(ə)r/ Embryology.
A relatively small blastomere formed by unequal segmentation in the fertilized ovum, such as one of those found at the animal pole of an amphibian ovum. Cf. macromere n.
ΘΚΠ
the world > life > biology > biological processes > procreation or reproduction > embryo or fetus > [noun] > blastula
periblastula1876
macromere1877
micromere1877
blastula1887
amphiblastula1888
1877 T. H. Huxley Man. Anat. Invertebrated Animals viii. 483 The vitellus divides into two unequal masses, of which the larger is termed by Rabl the ‘vegetative’ and the smaller the ‘animal’ cell, somewhat inconvenient names which may be replaced by ‘macromere’ and ‘micromere’.
1886 Jrnl. Royal Microsc. Soc. 6 224 The segmentation resembles that of other molluscs, the ‘micromeres’ appearing at the formative pole by separation of the ‘protoplasmic’ portion of the ‘macromeres’.
1909 J. W. Jenkinson Exper. Embryol. 185 In the next stage the clear vegetative cells derived (presumably) from the micromeres wander in to form the primary mesenchyme.
1969 R. F. Chapman Insects xviii. 349 In Hypogastrura cleavage is unequal with the formation of micro- and macro-meres.
1984 L. W. Browder Developmental Biol. (ed. 2) x. 444 This [unequal division] produces four small cells, the micromeres, clustered at the vegetal pole and four large cells, the macromeres.
1995 Proc. National Acad. Sci. U.S.A. 92 8180 Only the four micromeres that arise at the vegetal pole [of the sea urchin embryo] at the fourth division appear to be autonomously specified.
Derivatives
ΚΠ
1877 T. H. Huxley Man. Anat. Invertebrated Animals viii. 498 The edges of the micromeral layer.
This entry has been updated (OED Third Edition, December 2001; most recently modified version published online March 2022).
<
n.1877