Warm-blooded Fish?

DIY News writes "Scientists now have direct evidence that the north Pacific salmon shark maintains its red muscle at 68-86 degrees Fahrenheit, much warmer than the 47 F water in which it lives. The elevated muscle temperature presumably helps the salmon shark survive the cold waters of the north Pacific and take advantage of the abundant food supply there. The heat also appears to factor into the fish's impressive swimming ability."

Comments

Other warm-blooded "cold-blooded" creatures

[G4from128k]

Many insects also create intentionally elevated body temperatures (generally through shivering). Moths, bees, dung beetles all generate heat to enable greater activity under cold conditions.

For example. Honeybees generate heat in the winter to keep the hive warm and use heat to kill predatory wasps -- surrounding the wasp, heating up to 45 C (113 F) and killing the attacker.

Not surprising, and not really "warm-blooded"

[dpbsmith]

The distinction is not between "cold-blooded" and "warm-blooded" animals but between poikilotherms, whose body temperature is the same as that of the environment, and homeotherms, whose body temperature is closely regulated and held within a normal range of a couple of degrees or less

On the one hand, practically every poikilotherm that's been studied actually thermoregulates in some ways. Very few of them truly assume the temperature of their environment.

On the other hand, "maintaining" temperature at "68-86 degrees Fahrenheit" -- 77 degrees plus or minus 9--is far from comparable to the degree of thermoregulation shown by mammals. Nine degrees too high or too low is enough to kill you, and most mammals.

It's interesting to learn how another kind of poikilotherm performs a crude kind of thermoregulation, but by no means earthshaking.