Opah fish can regulate your whole body temperature
The opah fish are able to capture heat through its fins, isolated by a generous layer of godura, and keep its blood and organs warm while it swims to a depth of hundreds of meters. A study detailing this finding was published by the journal Science.
Other fish, such as tuna, can warm certain parts of the body - so they move faster when they need to chase prey. But complete endothermia had never been noticed in such an animal before. And the fact that it appears right on opah, which is a fish of great depth, known to be slow and not chase prey (eat cornered animals) is surprising.
As a result, it was also discovered that opah is incredibly agile and can feed on squid or other fast-moving animals. They can also migrate and swim for long distances.
Fish can make your blood 3 degrees Celsius warmer than water - it may not sound like much to us mammals, but it requires sophisticated thermal engineering. Even more for an opah-sized bug: in the study, the fattest weighed 68kg, but specimens of 270kg have been found.