The characters from the Great Gatsby aren’t the only blue bloods in the news lately.
Researchers at the Alfred Wegener Institute for Polar and Marine Research in Germany have found that a specialized pigment in the blood of Antarctic octopods allows them to survive temperatures that often drop below freezing.
It’s all down to a respiratory pigment in their blood called haemocyanin that allows the octopus “to maintain an aerobic lifestyle at sub-zero temperatures,” said Michael Oellermann, who took part in the research. Haemocyanin also has the effect of making the octopods’ blood blue. (Learn more about the octopus.)
“Haemocyanin contains copper, which is the responsible ion for binding oxygen,” explained Oellermann in an email. “Haemoglobins contain iron instead, which gives our blood a red color.”
It’s not a question of blood freezing.
“The reason why octopus blood does not freeze at -1.9 degrees C [28.58 degrees Fahrenheit] is that they are isosmotic, which means that their blood shares the same salinity as the surrounding seawater,” explained Oellermann.
The problem in very cold temperatures is that, without special adaptations, the aerobic process would, in most cases, shut down.
“Cold temperatures increase oxygen affinity to the extent that oxygen cannot be released in the tissue anymore,” explained Oellermann, making survival in waters that can drop to as low as 29 degrees Fahrenheit a challenge to say the least.
The researchers looked at a particular species of Antarctic octopod called Pareledone charcoti and compared it with temperate and warm-adapted octopods to observe the difference in how cold-water octopods transport oxygen in their blood.
“Pareledone charcoti decreased the oxygen affinity of its haemocyanin to counter the adverse effect of temperature on oxygen binding accompanied by changes in their protein sequence, to assure sufficient oxygen supply to its tissues and organs,” explained Oellermann.
Octopods likely developed the adaptation because they require a lot of oxygen compared to other invertebrates, notes Oellermann, and because they are largely non-migratory and must instead adapt to their environment.
In contrast, said Oellermann, Antarctic icefish survive in the same frigid environment by dint of their lower oxygen demand, rather than though the adapted system of oxygen transport employed by their blue-blooded neighbors.
Interestingly, the same adaptation may be what allows octopods to survive temperatures on the other end of the thermometer, such as the 86-degree F heat often found near thermal vents.