Age related changes in ovarian follicular kinetics in the Indian skipper frogRana cyanophlyctis (Schn.)

Abstract

Changes in ovarian follicular kinetics were studied in relation to aging in the Indian skipper frog Ran a cya noph ly cti s. Age was determined by skeletochronology, by counting the number of growth rings and lines of arrest of growth from the cross sections of 4th phalange of 4th toe. For follicular kinetics study oocytes were counted under binocular using 10% of Bouin's fixed ovary and they were classified into first growth phase, medium-sized second growth phase, large-sized second growth phase and atretic follicles. Analysis of phalangeal cross sections indicated that frogs ranging 14-54 g in body weight and 4·9-8·9 cm in body size showed 1-7 year rings. Frogs that weighed 14-16 g showed 1 year ring, and contained immature ovaries; those with 18 g body weight had one to two year rings, in which second growth phase oocytes appeared for the first time in the primiparous ovary. Frogs with 20-54 g body weight showed 2-5 year rings in which ovary contained 5-24% of second growth phase oocytes. Further, body weight, body size, ovarian weight, number and size of second growth phase oocytes and total number of oocytes showed a significant (P < 0·05) positive correlation, while, the number of first growth phase and atretic follicles showed a poor correlation with age. The results suggest that in nature, the age of Rana cyanophlyctis ranges between 1-7 years. Phalangeal growth rings are formed annually. Females attain sexual maturity in 2nd year. Frogs with 2-5 years of age may constitute breeding females. Body weight, body size, ovarian mass, number of second growth phase and total oocytes, and egg size increase with age up to 5 years.