It’s the warm fish in a cold pond.

A new study published in the journal Science has identified the world’s first fully warm-blooded fish: the car tire-sized opah, or moonfish.

Unlike birds and mammals, which warm their bodies above the ambient temperature, fish, amphibians and reptiles are generally classified as cold-blooded, meaning they use external means to control body heat. Some fish can generate bursts of warmth with swim muscles to help them during times of activity, but the opah is the first fish found to use heat to warm its heart and brain.

The opah lives almost exclusively in the deep ocean, where fish are usually sluggish due to the low temperatures. “At these depths, even predatory fish tend to be slow-moving, waiting patiently for prey to come by rather than actively chasing it down,” The Washington Post notes.

Because the opah has a specialized set of wing-like fins that can produce heat, it’s able to have a competitive advantage and live as a quick, active predator, the National Oceanic and Atmospheric Administration reported.

“Before this discovery I was under the impression this was a slow-moving fish, like most other fish in cold environments,” Nicholas Wegner, a fisheries biologist with NOAA, said in a press release. “But because it can warm its body, it turns out to be a very active predator that chases down agile prey like squid and can migrate long distances.”.. see more

source: huffingtonpost