First Fully Warm-Blooded Fish Identified!

This is cool:

"The opah, or moonfish, is the first known fully warm-blooded fish, according to a study published in the journal Science.
...
Certain other fish, such as some sharks and tuna, have what’s known as 'regional endothermy,' or limited warm-bloodedness. It allows them to stay active in colder depths, as well as shallower waters. But the fully warm-blooded opah are unlike all other fish, at least so far as we know it."