TEMPERATURE-DEPENDENCE OF OOCYTE CLEAVAGE IN 3 THERMOPHILICALLY DIFFERENT FROGS OF THE GENUS RANA

The duration of the mitotic cycle (τ0) at different temperatures at the time of synchronous cleavage division of oocytes of frogs Rana temporaria L., Rana arvalis Nilss. (= Rana terrestris Andr.) and Rana ridibunda Pall. has been studied. The first species is the least, and the last the most, thermophilic. In the semilogarithmic scale, the dependence of τ0 on temperature is linear in the middle of the temperature scale, and is limited on both sides by inflexion points. This zone comprises the temperatures at which the larvae develop normally. For R. temporaria these temperatures are between 11-23°C. for R. arvalis 13-24°C and for R. ridibunda 16-27°C. At the midpoints of each zone (17.5, 18.5 and 21.5°C respectively) there is no difference in τ0 between the species. At the same temperature, however, the mitotic cycle is the shortest for R. temporaria, is somewhat longer for R. arvalis and is the longest for R. ridibunda. The difference in the optimal temperature zones agree with different thermal stabilities of the cells and proteins of these species. © 1979.