First Warm-Blooded Fish Discovered

“According to the new study, ..., the [opah’s] blood vessels in the tissue are set up so that the vessels carrying cool, oxygenated blood from the gills to the body are in contact with the vessels carrying warm, deoxygenated blood from the body to the gills. As a result, the outgoing blood warms up the incoming blood, a process called counter-current heat exchange.”