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World’s first warm-blooded fish is faster and smarter than its cold-blooded cousins


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Well, this changes my notion of what a fish is.

The opah is equipped with blood vessels that carry warm blood to the fish’s gills. These wrap around other blood vessels that carry cold blood back to the body after absorbing oxygen from water, ensuring a core body temperature that is consistently about 5 degrees Celsius higher than the surrounding water. NOAA says this is known in engineering as “counter-current heat exchange.”

Lead author of the new paper and fisheries biologist Nicholas Wegner said this unique circulation system allows the fish to move faster, see better, and react more quickly than its cold-blooded counterparts.

Related: 35 facts that will make you never want to eat fish again

“Before this discovery I was under the impression this was a slow-moving fish, like most other fish in cold environments,” Wegner said. “But because it can warm its body, it turns out to be a very active predator that chases down agile prey like squid and can migrate long distances.”

Wegner added that the higher body temperature should increase the opah’s muscle output and capacity, while also boosting eye and brain function. The fish also is able to stay in deep water longer without risking damage to their heart and other organs. Fatty tissue surrounding the gills, heart and muscle tissue are said to act as an insulator that protects the fish against icy waters.

“Nature has a way of surprising us with clever strategies where you least expect them,” Wegner said. “It’s hard to stay warm when you’re surrounded by cold water but the opah has figured it out.”

Via Washington Post

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