Warm-Blooded Fish Discovered

[Yazata]

Researchers at NOAA's (the US National Oceanic and Atmospheric Administration's) Fisheries Science Research Laboratory in San Diego, have discovered that a fish called an Opah, apparently widely distributed around the world but in this case caught and tagged off the Channel Islands in Southern California, is (sorta) warm-blooded.

Opah were thought to be slow and sluggish swimmers, but they are now known to be fast predators. They don't maintain a set body temperature the way we do, but keep the blood flowing through their muscles at about five degrees C. warmer than the ambient sea temperature.

Apparently their hearts and muscles warm their blood and there's kind of heat exchanger arrangement where blood vessels come near each other so that warmer blood warms cooler oxygenated blood coming from the gills.

http://www.sciencetimes.com/articles/639...d-fish.htm

[C C]

Does seem to have a functional system for that rather than just falling out of size. It's difficult to imagine the prehistoric fish Leedsichthys not being mildly endothermic in the unimpressive way, simply because it was so gigantic. But instead the speculation usually swims around the more theatrically exciting Megalodon.

"It is theorized that the White shark stuck to the colder deeper waters and fed on early seals, while Megalodon stayed near shore in the warmer waters preying upon whales. This theory runs into problems because many believe that Megalodon was warm blooded and that its immense girth forced into deep water, not inshore estuaries. The entire basis of these arguments is placed on nothing more than the space between the serrations of the teeth which vary considerably from tooth to tooth. As sharks bodies are made of almost entirely cartilage it is near impossible for an entire shark body to be preserved. Thus all science has to argue over are the hard parts, teeth. Based on these two theories Megalodon was either a warm blooded predator that stalked whales and other mammals, or it was a cold blooded predator that terrorized large schools of fish. Until more evidence for the classification of Megalodon arises, most scientists hold fast to the theory that Megalodon was the great grandfather of the modern White shark."