breathinginbiology:

In May of 2015, the first warm blooded fish was discovered. Lampris guttatus (otherwise known as Opah or Moonfish) is a deep-sea dwelling endotherm,  meaning it internally regulates its body temperature. This is very unique because all other fish are ectotherms and rely on the environment as their heat source. The Opah’s endothermic nature means that it can swim faster, see better, and respond to its environment quicker.