Unlikely opah can keep much of its body warmer than its cold sea surroundings
NOAA Fisheries West Coast/Flickr (CC BY-NC-ND 2.0)
A fish that looks like a giant cookie with skinny red fins comes the closest yet among fishes to the whole-body warm-bloodedness of birds and mammals.
The opah (Lampris guttatus) has structures never before recognized in fish gills that may help conserve the warmth in blood, says Nick Wegner of the Southwest Fisheries Science Center in La Jolla, Calif. The unusual gills and other heat-saving features don’t achieve the high, stable body temperatures that define warm-blooded, or endothermic, mammals and birds. But measurements suggest that the opah can keep its heart and some other important tissues several degrees warmer than the deep, cold water where it swims, Wegner and his colleagues say in the May 15 Science.