Final answer:
Endothermy in fish is a rare characteristic found in species such as tuna, swordfish, and some sharks, which allows them to maintain higher body temperatures than their environment.
Step-by-step explanation:
The types of fish that exhibit endothermy include certain species such as tuna, swordfish, and some sharks.Unlike most fish that are ectothermic and rely on external environmental temperatures to regulate their body temperature, species that display endothermy can maintain a body temperature that is higher than the surrounding water. This unique adaptation provides them with enhanced metabolic rates, allowing them to sustain higher levels of activity, especially in colder waters. Endothermic fish have evolved mechanisms to conserve the heat generated by their muscles during locomotion, effectively warming their bodies above ambient water temperatures. This physiological trait is quite exceptional considering the evolutionary background of fishes.
Fish such as tuna and swordfish achieve their endothermic abilities by using a specialized blood vessel structure known as the rete mirabile, which functions as a heat exchanger that retains warmth within their bodies. Meanwhile, some sharks utilize their large swimming muscles to generate and retain heat, thereby maintaining their inner temperature.