First fully warm-blooded fish: The opah or moonfish

New research by NOAA Fisheries has revealed the opah, or moonfish, as the first fully warm-blooded fish that circulates heated blood throughout its body much like mammals and birds, giving it a competitive advantage in the cold ocean depths.

The silvery fish, roughly the size of a large automobile tire, is known from oceans around the world and dwells hundreds of feet beneath the surface in chilly, dimly lit waters. It swims by rapidly flapping its large, red pectoral fins like wings through the water.

That warm-blooded advantage turns the opah into a high-performance predator that swims faster, reacts more quickly and sees more sharply, said fisheries biologist Nicholas Wegner of NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla, Calif., lead author of the new paper.

Wegner realized the opah was unusual when a coauthor of the study, biologist Owyn Snodgrass, collected a sample of its gill tissue. Wegner recognized an unusual design: Blood vessels that carry warm blood into the fish’s gills wind around those carrying cold blood back to the body core after absorbing oxygen from water.

The design is known in engineering as “counter-current heat exchange.” In opah it means that warm blood leaving the body core helps heat up cold blood returning from the respiratory surface of the gills where it absorbs oxygen. Resembling a car radiator, it’s a natural adaptation that conserves heat. The unique location of the heat exchange within the gills allows nearly the fish’s entire body to maintain an elevated temperature, known as endothermy, even in the chilly depths. “There has never been anything like this seen in a fish’s gills before,” Wegner said.

“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.”

(read more) Science Daily || photo: NOAA || [paper]

touchtheowl  asked:

What was going on in more northern colder places where cold blooded animals can't survive while reptilian dinosaurs were the dominant thing? Were there any larger mammals or...?

Dinosaurs were warm blooded, so, they lived up there too. And in the Southern cold places. 

anonymous asked:

hello, fellow dino enthusiast! here's something i've been totally confused about for a long time, so- from your research learning, what do you know about the body temperature of dinosaurs? hot-blooded, warm-blooded, something in between, not uniform for the entire clade?

The latest study suggests they were in the middle - they grew fast, we know that, and were probably active, like endotherms; but not as fast growing and active as endotherms; it also varied greatly depending on what kind of dinosaur you were. Still, given that these are extinct organisms, determining this kind of information is difficult. Below is a recent study on the topic, plus some responses (some of the methodology was criticized, but then these criticisms were rebuked).