The morphological and physiological changes during the reproductive cycle of the female rock lizard, Agama atra Daudin, 1802

Van Wyk, J. H. (1982-06)

Thesis (MSc) -- Stellenbosch University, 1982.


ENGLISH ABSTRACT: Morphological and physiological changes during the annual reproductive cycle of the female oviparous lizard, Agarna atra, are described. 1 • 2. 3. 4. 5. 6. 7. 8. The onset of the breeding cycle was marked by vitellogenic ovarian hyper= trophy (September) and ovulation of the first clutch occurred in c;x:tober, after which a second clutch was produced. During February no vitellogenic females were collected. The onset and tennination of the breeding cycle, correlated with the spring and aufumnal equinox as well as increased and decreased mean monthly air temperatures. Photothennal regimes ( 14L : 10 D and 25 - 45 °C) induced vitellogenesis in females collected during the winter months. Histological changes of the growing oocyte were studied. CXJgonial pro= liferation, oogenesis and folliculogenesis in Agama. atra appeared to be consistant with the general squamate pattern. Post-ovulatory and two types of atretic follicles are described. The fatbody cycle showed an inverse correlation with ovarian hypertrophy. Total plasma cholesterol varied between 200 and 350 -1 mg. 1 OOml • A decrease was correlated with ovarian hypertrophy and fatbody depletion. The total plasma protein concentration decreased during vitellogenesis· and increased before ovulation. The plasma proteins separated into five major fractions upon cellulose acetate electrophoresis. Ovarian hypertrophy was accompanied by an increase in fraction II (similar m::>bility .as human "Beta-globulins"). Fractions V ("albumin"), IV and III ("Alpha-globulins") were conccmitantly decreased. Plasma calcium concentrations increased significantly (P<0.001) during vitellogenesis. A post-ovulator.1 progesterone surge (7450 pg. 0.2ml-1) with the presence of well developed corpora lutea. The onset of a second vitellogenic cycle ~fs evident during relative high prbgesterone levels (1 500 pg. 0.2rill ). ' 9. The oviducal index showed a high correlation with ovarian development, indicating oestrogenic activity. 10. Oestrogen and oestrogen plus progesterone treabnent resulted in increased plasma vitellogenic paramters in the male, Agama atra. Progesterone alone had no effect. 11. Both PMSG and HCG treabnent (4 IU per lizard) induced vitellogenesis in females containing quiescent ovaries, although PMSG was found to be more potent in inducing ovulation. 12. No significant effect of arginine-vasotocin and oxytocin on oviposition could be observed. KEY WORDS: Squamata, Ag3I1la, Female breeding season, environmental, seasonal changes, ovarian histology, fatbody, cholesterol, plasma proteins, calcium, oviduct, progesterone, vitellogenesis, gonadotropins, oviduct contractility.

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