Seasonal variation in plasma and corpus luteum oestradiol-17β and progesterone concentrations of the lizard <i>Cordylus p. polyzonus</i> (Sauria: Cordylidae)

Abstract

Seasonal variation in plasma and corpus luleum oestradiol-17β and progesterone concentrations of the viviparous lizard Cordylus p. polyzonus is described. Sleroid concentrations were measured by radioimmunoassay. Plasma oeslradiol-17β concentration increased from basal values in late autumn (May) and peaked in mid-spring (October), during which time females were vitellogenin Plasma oestradiol-17β concentration declined to basal values in late spring (November) when females ovulale, remaining low until the onset of the nexl vitellogenic phase in autumn. Plasma progesterone concentrations of previlellogenic and early vilellogenic females (April-July) were basal, but increased during the laler slagas of vilellogenesis (August-October). Following ovulation in November, plasma progesterone concentrations were high throughout pregnancy, declining to basal values in April when parturition occurred. Oestradio-17β was detectable in freshly formed corpora lutea (corpora haemorargica) during the first month of pregnancy (November), but declined to undetectable values thereafter. Corpus luleum progesterone concentration gradually increased as pregnancy proceeded, reaching a peak two months before birth, bul declined thereafter. Progesterone concentration of postpartum degenerating corpora lutea (corpora albicantia) was considerably lower than that of corpora lutea during geslation.