Embryonic temperature tolerance in brown frogs

Abstract

Embryonic temperature tolerances of five species of Japanese brown frogs, Rana japonica, R. tsushimensis, R. dybowskii, R. okinavana and R. tagoi, were reported. High-temperature limits at which a half of morulae or blastulae died before stage 25 (completion of operculum) are 33 C in R. japonica, 31 C in R. tsushimensis, 29 C in R. dybowskii and R. okinavana, and 25 C in R. tagoi. Low-temperature limits are above 4 C in R. japonica and below 4 C in R. tagoi. High-temperatue limits seem to correlate not with air temperature or shape of egg mass but with higher limit in the temperature fluctuation of breeding waters and egg diameter.