Why are some cyprinodont fishes able to survive in hot springs?

Some cyprinodont fishes are able to survive in hot springs because they are among the hardiest of all fishes and have developed specialized physiological adaptations that allow them to inhabit such rigorous environments.12

These fishes appear capable of surviving in water temperatures that approach the coagulation point of protoplasm, a feat that distinguishes them from many other aquatic species. While the specific molecular details of these physiological mechanisms remain relatively poorly known, these adaptations enable them to thrive in thermal springs where temperatures can exceed 42 °C (100 °F).12