Dynamics of oogenesis in the tropical anuran Rana tigrina (Amphibia: Ranidae) with special reference to vitellogenic cycles in wild-caught and captive flogs.
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Date
1994-09
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Abstract
The ovarian cycle of Rana tigrina was 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 oocytes.
The number of first growth phase oocytes fluctuated from 65 to 95%. The fluctuation
was inversely correlated with the second growth phase oocytes indicating a 30 to 35%
annual turnover rate of oocytes in the frog. The final egg number/ovarian mass is positively
correlated with the snout-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 eggs/100 g body
mass and the total volume (V) of eggs/frog were highly correlated.
Frogs living in captivity produced fewer eggs compared to the wild ones (3594 ± 227
in captive vs 4704 ± 317 in wild frogs). Also, these frogs failed to breed though they
showed amplexus with breeding males. Injection of desoxycorticosterone acetate however induced
spawning in 4 out of 5 frogs. They released about 3000 eggs each. Captivity seems to mainly
impair breeding and to a little extent the vitellogenic growth of oocytes in R. tigrina.
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Keywords
Frog, oogenesis, fat body
Citation
Hoque B, Saidapur S K. Dynamics of oogenesis in the tropical anuran Rana tigrina (Amphibia: Ranidae) with special reference to vitellogenic cycles in wild-caught and captive flogs. Journal of Biosciences. 1994 Sep; 19(3): 339-352.