First Fully Warm-Blooded Fish Discovered

The Opah (Lampris guttatus), also known as the moonfish, has become the first fish discovered that is entirely endothermic (warm-blooded) using a mechanism that has never been seen before in a fish.

They are a large round fish, usually weighing between 60 – 200lbs found up to 1000 feet beneath the surface where they live in very cold and dark waters. Until now, it has been a mystery why they are exceptionally high performance predators with brilliant sight, reaction speeds and stamina giving it a highly competitive edge over other animals competing for resources in the area. They are known to be capable of hunting agile prey such as squid, and they’ve shown the ability to migrate vast distances. Although some fish such as tuna and sharks are known to have a partially warm-blooded system known as regional endothermy which allows them to stay active at colder depths, the Opah has evolved an entirely unique car radiator-like system to keep it warm in icy water. body temp They continually flap their pectoral fins to keep their core temperature at 41 degrees Fahrenheit higher than the environment. The Opahs vascular system means warm blood leaving the fishes core warms the cold blood returning from the gills. gillsA sample of an Opahs gill tissue has revealed a net of tightly packed arteries and veins, known as a therete mirabile. This ensure that the blood vessels transport warm blood to the gills, then around vessels, warming up the cold blood moving back to the core of the body after absorbing oxygen from the surrounding waters. This counter-current heat exchange system prevents cold blood from decreasing the core temperature of the fish. This discovery goes on to prove how little we know about our ocean depths. For more information: http://www.sciencemag.org/content/348/6236/786

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