Dynamics of oogenesis in the tropical anuranRana tigrina(Amphibia: Ranidae) with special reference to vitellogenic cycles in wild-caught and captive flogs

摘要

The ovarian cycle ofRana tigrinawas analysed by quantifying the developing oocytes (classified into stages on the basis of diameter) and atretic ones at monthly intervals. Stages I to IV represent oocytes in the first growth phase and the remaining ones the vitellogenic or second growth phase. Stages I–III occurred year round but exhibited significant 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 specimens. Of the 30 to 35 second growth phase oocytes, 25 to 28 reached ovulatory sizes by June. After spawning the ovarian mass declined drastically 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 oocyte