By Erik Stokstad
Researchers have discovered the first fish that can keep its entire body warm, much like mammals and birds. The opah, or moonfish, lives in deep, cold water, but it generates heat from its massive pectoral muscles. And it conserves that warmth thanks to body fat and the special structure of blood vessels in its gills.
“It’s a remarkable adaptation for a fish,” says Diego Bernal, a fish physiologist at the University of Massachusetts, Dartmouth, who was not involved in the study. Having a warm heart and brain likely allows the little-known fish to be a vigorous predator, the researchers suspect.
Water will take the heat right out of most creatures. So fish typically remain the temperature of the water they swim in. And that, in turn, limits their biological functions in colder water, especially cardiovascular endurance. There are partial exceptions: Tuna, billfish, and some sharks can temporarily raise the temperature of their body muscles while they hunt, but they must return to warmer waters to bring their core temperature back to normal.
|