Seasonal variation in plasma and corpus luteum oestradiol-17 and progesterone concentrations of the lizard Cordylus p. polyzorlus (Sauria: Cordylidae)

ENGLISH ABSTRACT: Seasonal variation in plasma and corpus luteum oestradiol-17 and progesterone concentrations of the viviparous lizard Cordylus p. potyzonus is described. Steroid concentrations were measured by radioimmunoassay. Plasma oestradiol-17 concentration increased from basal values in late autumn (May) and peaked in mid-spring (October), during which time females were vitellogenic. Plasma oestradiol-17 concentration declined to basal values in late spring (November) when females ovulate, remaining low until the onset of the next vitettogenic phase in autumn. Plasma progesterone concentrations of previtellogenic and early vitellogenic females (April-July) were basal, but increased during the later stages of vitellogenesis (August-October). Following ovulation in November, plasma progesterone concentrations were high throughout pregnancy,d ecliningt o basal values in April when parturition occurred. Oestradiol-17 was detectable in freshly formed copora lutea (corpora haemorargica) during the first month of pregnancy (November), but declined to undeteclable values thereafter. Corpus luteum progesterone concentration gradually increased as pregnancy proceeded, reaching a peak two months before birth, but declined thereafter. Progesterone concentration of postpartum degenerating corporal lutea (corpora albicantia) was considerably lower than that of (corpora lutea during gestation. ********* AFRIKAANSE OPSOMMING: Seisoenale variasie in plasma- en corpus luteum-oestradiol-17 - en progesteroonkonsentrasies van die lewendbarende akkedis Cordylus p. polyzonus, word beskryf. Die stero dkonsentrasie is bepaal deur radioimmunolog. Plasma-oestradiol-17 -konsentransie neem toe vanaf basale waardes gedurende laatherf is (Mei ) en bereik ‘n piek in middel lente (Oktober) wanneer wyfies vitellogenies is. Plasma-oestradiol-17 -konsentransie neem af na basale waardes in laat lente( November) wanneer wyfies ovuleer, en bly laag tot die aanvang van die volgende vitellogeniese fase in die herfs. Plasma progesteroonkonsentrasies van previtellogeniese en vroe vitellogeniese wyfies (April-Julie) is basal, maar neem toe gedurende die later stadia van vitellogenese (Augustus-Oktober). Na ovulasie in November is plasma-progesteroonkonsentrasies hoog en bly so deur swangerskap, gevolg deur 'n afname tot basale waardes in April wanneer geboorte plaasvind. Oestradiol-17 was bepaalbaar in die nuutgevormde corpora lutea (corpora haemorargica) tydens die eerste maand van swangerskap (November), maar neem af na onbepaalbare vlakke daarna. Corpus luteum-progesteroonkons