It’s a basic biology fact: Birds and mammals are warm-blooded, while reptiles, amphibians and fish are cold-blooded.
But new research is turning this well-known knowledge on its head with the discovery of the world’s first warm-blooded fish — the opah.
In a paper published Thursday in Science, researchers from the National Oceanic and Atmospheric Administration describe the unique mechanism that enables the opah, a deepwater predatory fish, to keep its body warm. A specially designed set of blood vessels in the gills allows the fish to circulate warm blood throughout its entire body.
Most fish that live where the opah does — that is, hundreds of feet deep, in some of the ocean’s darkest and coldest places — are sluggish, thanks to the low temperatures. But the opah has many features usually associated with a quick-moving, active predator.
These characteristics make the opah “a curiosity,” said Heidi Dewar, a researcher at NOAA’s Southwest Fisheries Science Center and one of the paper’s authors.
