other fish. Their blood is transparent because they have no hemoglobin and/or only defunct erythrocytes. Their metabolism relies only on the
oxygen dissolved in the liquid blood, which is believed to be absorbed directly through the skin from the water. This works because water can
dissolve the most oxygen when it is coldest. In five species, the gene for myoglobin in the muscles has also vanished, leaving them with
white instead of pink hearts. (Photo by uwe kils)
