Nature's Surprise: First Ever Warm-Blooded Fish Discovered

(CBS SF) -- As if this circular silver and orange fish wasn't strange enough, researchers recently discovered it also has warm blood, giving it a unique advantage.

It's the first time any fish has been classified as warm-blooded, making the opah (Lampris guttatus) different from its ecotherm brethren who depend on heat from the environment to stay warm.

The opah stays warm by flapping its fins rapidly and using fat deposits around its gills and muscles.

"There has never been anything like this seen in a fish's gills before," study leader Nicholas Wegner, a biologist at the National Oceanic and Atmospheric Administration (NOAA) Fisheries' Southwest Fisheries Science Center in La Jolla, California, told Live Science. "This is a cool innovation by these animals that gives them a competitive edge. The concept of counter-current heat exchange was invented in fish long before [humans] thought of it."

Countercurrent heat exchange refers to the process between blood vessels to exchange cool, oxygenated blood with warm, oxygenated blood.

As a result, this process allows the opah to hunt in deep water for long periods of time than cold-blooded fish who struggle to keep warm during deep dives.

No matter how deep these fish dive and cold the water gets, their body temperature stays about 9 degrees Fahrenheit.

"As a result, the muscles can contract faster, the temporal resolution of the eye is increased, and neurological transmissions are sped up," Wenger said. "This results in faster swimming speeds, better vision and faster response times."