The body temperatures of ectotherms, like lizards and turtles, can fluctuate with the environment. How do ectotherms maintain homeostasis?

Endotherms, such as birds and mammals, use metabolic heat to maintain a stable internal temperature, often one different from the environment. Ectotherms, like lizards and snakes, do not use metabolic heat to maintain their body temperature but take on the temperature of the environment.

the answer will be a) proteins i believe