Seasonal rhythms of development and temperature selection in larval bullfrogs, Rana catesbeiana Shaw

Tadpoles were placed in 25°C tanks with long (16L:8D), short (8L:16D), and natural photoperiods. For the first 2 wk in the 25°C tanks, development was rapid (0.4 stages.d^-1) in early and midsummer but very slow (0.02 stages.d^-1) in early winter. During this initial 2-wk period, the temperatures selected in early and midsummer (28.4°C) were higher than those selected in early winter (24.0°C). After 2 wk in the 25°C tanks, the long-photoperiod group (relative to the short-photoperiod group) showed a slight decrease in development in early summer, no difference in midsummer, and a definite increase in early winter. Temperature selection was not altered by photoperiod length. Endogenous annual rhythms for development and temperature selection are apparently present in R. catesbeiana tadpoles. -from Authors