LONGITUDINAL-STUDY OF OVARIAN DYNAMICS IN FEMALE GRAY TREEFROGS (HYLA-CHRYSOSCELIS)

Biopsies were performed to study the ovarian dynamics of a breeding po pulation of free-living female gray treefrogs, Hyla chrysoscelis, in w estern Tennessee. This study used a longitudinal design in which indiv idual females were biopsied up to four separate times in the same bree ding season. All of the postspawning ovaries (n = 149) contained a ser ies of enlarged follicles (mean follicle diameter = 0.305 mm), a condi tion that apparently facilitates repeated spawning during a prolonged breeding season. The size-frequency distribution of follicles remainin g in the ovary after spawning was similar among all females (unimodal between 0.10 and 0.30 mm diameter) indicating that vitellogenic growth of this pool of follicles is slowed or arrested while another series of larger follicles (those that will comprise the next clutch) nears m aturation. The average size of the follicles remaining in the ovary af ter spawning was not correlated with female body size, clutch number, time (month) during the breeding season, the number of days since last oviposition, or the number of days it took females to oviposit their next clutch. Thus, the ability to oviposit more than one clutch in a b reeding season may depend primarily on the foraging success of females , an idea supported by the observation that fat bodies were generally not available as an energy source for the production of multiple clutc hes after the start of the breeding season. Ovarian biopsies performed in Nov. on captive frogs indicated that females may enter winter dorm ancy with or without enlarged ovaries, a condition that may also depen d on the nutritional condition of the female.