Ice Fish showing white gills
Base H - Signy Island Antarctica

  ©Copyright P. Ward - picture taken 1985 / 86

Ice fish have no respiratory pigment - usually the red haemoglobin that gives other vertebrates red blood. There isn't an alternative chemical instead, there just isn't anything that does the same job. Their blood is a clear liquid and gives them an eerie ghostly look particularly of the gills which are white rather than the bright red of other fish.

Oxygen like most gases dissolves better in cold water and this characteristic along with a blood volume larger than other fish means that the ice-fish can get along fine without a carrier molecule like haemoglobin for their oxygen. They will benefit from having less need for iron (found in haemoglobin) and not needing to use energy and protein to make a respiratory pigment.

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