Mesothermy is a biological phenomenon in which an organism maintains a stable core body temperature higher than its surroundings, but does not have a completely uniform internal temperature like endotherms. This allows for greater energy efficiency compared to fully endothermic animals, as less energy is required to maintain a stable body temperature. Mesothermy is found in a variety of animals, including certain fish, sharks, and insects. Research in mesothermy focuses on understanding the physiological mechanisms that allow these organisms to regulate their body temperature and the ecological benefits of this adaptation.