Biologist Nick Wegner, coauthor of the Science paper, holding a recently captured opahWIKIMEDIA, USA NOAA FISHERIES SOUTHWEST FISHERIES SCIENCE CENTERFish are generally a cold-blooded set. No species had been documented to stray very far from ecothermy, which makes the body temperatures of most fish—along with reptiles, amphibians, and insects—track with environmental conditions. But researchers have determined that one species of fish, the opah, or moonfish (Lampris guttatus), is warm-blooded and can regulate its body temperature even at the frigid depths of its deep-sea habitat.
The opah was long considered a slow-moving fish, like many of the other species that inhabit the deep sea. But scientists with the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center (SFSC) reported in Science today (May 15) that the species can keep its body temperature at about 5° C warmer than the surrounding water by pumping its slender pectoral fins, a physiological adaptation that would allow it to be a more active predator.
“Before this discovery I was under the impression this was a slow-moving fish, like most other fish in cold environments,” coauthor and SFSC biologist Nicholas Wegner told BBC News. “But because it can warm its body, it turns out to be a very active predator that chases down agile prey ...
