Cold fins, warm heart? Strange but true, scientists say.
In a discovery that defies conventional biology, a big fish that lives deep in the Pacific Ocean has been found to be warm blooded, like humans, other mammals and birds.
Researchers from the National Oceanic and Atmospheric Administration (NOAA) determined that unlike other fish, opah generate heat as they swim and distribute the warmth throughout their entire disc-shaped bodies by special blood vessels. Special “counter-current heat exchangers” in their gills minimize heat loss, allowing the deepwater predators to keep their bodies several degrees above the water temperature 250 feet down.
“There has never been anything like this seen in a fish’s gills before,” said biologist Nick Wegner, the lead author of the report.
Though some species of fish can temporarily warm their swim muscles, including tuna and some sharks, “whole-body endothermy” has distinguished mammals and birds from fish and reptiles, which draw heat from their environments.
“The opah appears to produce the majority of its heat by constantly flapping its pectoral fins, which are used in continuous swimming,” Wegner told Live Science.
His colleague Heidi Dewar told The Washington Post, “I think that it’s really exciting that we spend so much time studying especially these larger fish to find something that’s completely unique and has never been seen before in any fish.”
Their team’s findings are published in the May 15 issue of Science.
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SOURCE: USA Today, Michael Winter