mesolecithaladj.
/ˌmɛsə(ʊ)ˈlɛsᵻθl/, /ˌmɛzə(ʊ)ˈlɛsᵻθl/, /ˌmiːsə(ʊ)ˈlɛsᵻθl/, /ˌmiːzə(ʊ)ˈlɛsᵻθl/, U.S. /ˌmɛzoʊˈlɛsəθ(ə)l/, /ˌmɛsoʊˈlɛsəθ(ə)l/; see also meso- comb. form. Zoology.
Designating an egg or egg cell having a moderately large yolk. Also: = centrolecithal adj. at centro- comb. form (rare).
ΚΠ
1909 Cent. Dict. Suppl. Mesolecithal, in embryol., a term applied to certain eggs, like those of most arthropods, in which the yolk at an early developmental stage lies in the center and is enveloped by a layer of blastodermic cells: same as centrolecithal and perilecithal.
1926 H. E. Jordan & J. E. Kindred Textbk. Embryol. v. 31 On the basis of a difference in the amount of yolk, eggs may be divided into three classes; meiolecithal eggs, those with little yolks; mesolecithal eggs, those with a moderate amount of yolk; and polylecithal eggs, those with relatively much yolk.
1974 D. Webster & M. Webster Compar. Vertebr. Morphol. xviii. 459 Smaller amounts of yolk are deposited in the mesolecithal eggs of amphibians and teleosts.
1986 A. S. Romer & T. S. Parsons Vertebr. Body (ed. 6) v. 109 The frog has a characteristic mesolecithal egg, and the same type is found in urodeles, lungfishes, lower actinopterygians, and lampreys;..it is reasonable to conclude that the mesolecithal egg was characteristic of the ancestral vertebrates.
This is a new entry (OED Third Edition, September 2001; most recently modified version published online March 2022).
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adj.1909