Long-Term Heat Tolerance and Accelerated Metamorphosis: Hot Spring Adaptations of .

Extreme temperatures are a major threat to the survival of ectotherms such as amphibians. The tree frogs belonging to the genus have accomplished a latitudinal distribution and a wide range of thermal adaptations. In particular, , referred to as the "hot spring frog", has been reported to tolerate extremely high temperatures. However, it is unclear how the heat tolerance and metamorphic strategies of this species vary among populations at different temperatures. We therefore conducted long-term heat tolerance experiments on multiple populations of tadpoles and their congenic species to determine their survivability and development speed. We observed heat tolerance differences between and exhibited the highest tolerance among all species, and the Seranma hot spring population showed the highest survival rate and accelerated development speed. However, at temperatures higher than 35°C, they could not survive until the completion of metamorphosis, contrary to previous field observations. Our behavioral experiment showed attenuation of the high temperature preference of tadpoles associated with developmental stages, suggesting that they can tolerate extreme temperatures for a limited time window during their development until metamorphosis.