The icefishes (or white-blooded fishes) are a family (Channichthyidae) of perciform fish found in the cold waters around Antarctica and southern South America.

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. Also, their muscles (except the heart muscle) lack myoglobin. These extraordinary properties seem to be an adaptation to the extreme cold of their habitat. (Note that water temperature can drop below 0 °C (the freezing point of freshwater) in the Antarctic sea, but, on the other hand, stays rather constant.)

Channichthyidae are the only known vertebrates without hemoglobin. For a discussion of the discovery, genetic analysis and evolutionary implications of this condition, see the first chapter of Sean Carroll's book (referenced below). The chapter is titled "The Bloodless Fish of Bouvet Island".

Icefish feed on krill, copepods, and other fish.

There are fifteen known species of Icefish.

External links

• Fishbase info for Channichthyidae (Note: They are called crocodile icefish here, but only icefish elsewhere.)
• A story about the use of the icefish for medical research
• Carroll, Sean. "The Making of the Fittest" New York: W.W. Norton, 2006.

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