Japanese tadpoles can live and grow in natural hots springs, or onsen, with water temperatures as high as 46.1C (115 F). Living in onsen may benefit the tadpoles’ immune systems, speed their growth, and allow the tadpoles to survive on small volcanic islands where there are few other natural sources of fresh water.
https://www.sciencedaily.com/releases/2016/07/160726094317.htm