Fun Fact Friday: First Warm-Blooded Fish Found

Did you know that scientists recently discovered the first known warm-blooded fish, and that it was under everyone’s noses all along? It’s true!

The opah (also known by a variety of other names, including sunfish, moonfish, and kingfish) is a relatively common fish for deep sea fisherman to encounter, and is often sold in fish markets. While this species of fish was well known, its warm-bloodedness was only discovered very recently. The opah (or Lampris guttatus, as pictured above) seems to have developed this characteristic in order to allow it to dive deeper into the ocean, in search of squid and other prey.

According to Wikipedia:

“Opahs are the first fish discovered to be completely warm-blooded. Although the salmon shark has the ability to regulate its blood temperature, allowing it to function in the frigid North Pacific waters, the opah is completely warm-blooded….exhibiting counter-current heat exchange in which the arteries, carrying warm blood, from the heart, warm the veins in the gills carrying cold blood. The gills are cooled by contact with cold water. The opah’s pectoral muscles, generate most of its body heat. The opah retains heat with insulating layers of fat, which insulates the heart from the gills, and the pectoral muscles from the surrounding water. The opah can consistently keep its entire body around 5 degrees Celsius warmer than its environment.”

As you can see, the opah is truly a unique fish! It makes you wonder what other science secrets will be found to be hiding in plain sight, in the future.

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