DYNAMICS OF OOGENESIS IN THE TROPICAL ANURAN RANA-TIGRINA (AMPHIBIA, RANIDAE) WITH SPECIAL REFERENCE TO VITELLOGENIC CYCLES IN WILD-CAUGHT AND CAPTIVE FROGS

The ovarian cycle of Rana tig,ina was analysed by quantifying the deve loping oocytes (classified into stages on the basis of diameter) and a tretic ones at monthly intervals. Stages I to IV represent oocytes in the first growth phase and the remaining ones the vitellogenic or seco nd growth phase. Stages I-III occurred year round but exhibited signif icant variation in their number. The number of stage II oocytes always dominated the other stages. Recruitment of oocytes to stages IV and V in April marked the initiation of vitellogenic growth in all specimen s. Of the 30 to 35% second growth phase oocytes, 25 to 28% reached ovu latory sizes by June. After spawning the ovarian mass declined drastic ally from 15 to 0.2% of body mass in July, Atresia was maximal (5%) in August. In other months, it was less than 1.5% of the total oocytes. Oogenic episodes occurred in March and July yielding new oocytes. The number of first growth phase oocytes fluctuated from 65 to 95%. The fl uctuation was inversely correlated with the second growth phase oocyte s indicating a 30 to 35% annual turnover rate of oocytes in the frog. The final egg number/ovarian mass is positively correlated with the sn out-vent length as well as body mass of the frogs. R. tigrina produces about 4000 eggs/100 g body mass. Further, the mean number of yolky eg gs/100 g body mass and the total volume (V) of eggs/frog were highly c orrelated. Frogs living in captivity produced fewer eggs compared to t he wild ones (3594+/-227 in captive vs 4704+/-317 in wild frogs). Also , these frogs failed to breed though they showed amplexus with breedin g males. Injection of desoxycorticosterone acetate however induced spa wning in 4 out of 5 frogs. They released about 3000 eggs each. Captivi ty seems to mainly impair breeding and to a little extent the vitellog enic growth of oocytes in R. tigrina.