Antarctic Octopus Gives New Meaning to 'Blue Blood'

An Antarctic octopus is giving new meaning to the phrase "blue blood," as a new study finds that the creature boasts unique blue pigments in its blood that allow it to survive ice-cold water, making it more resilient to climate change than other species.

You would think that the Antarctic Ocean, which can reach temperatures below freezing, would be inhospitable to any marine life. It can be hard to deliver oxygen to tissues in the cold due to lower oxygen diffusion and increased blood viscosity. However, frigid waters already contain large amounts of dissolved oxygen, and many creatures have learned to adapt to these extreme conditions.

This includes Antarctic fish, which possess blood pigments (e.g. haemoglobin) that reduce the need for active oxygen transport. But researchers wanted to know how others are able to sustain an oxygen supply in the cold - specifically, blue-blooded octopods.

So they collected and analyzed the haemolymph (a fluid equivalent to blood) from the Antarctic octopus, Pareledone charcoti. They also did this for two other octopus species collected from warmer climates: the Southeast Australian Octopus pallidus and the Mediterranean Eledone moschata.

"This is the first study providing clear evidence that the octopods' blue blood pigment, haemocyanin, undergoes functional changes to improve the supply of oxygen to tissue at sub-zero temperatures. This is important because it highlights a very different response compared to Antarctic fish to the cold conditions in the Southern Ocean," lead author Michael Oellermann, from Alfred-Wegener-Institute, Germany, said in a press release.

It turns out octopods have three hearts and contractile veins that pump "haemolymph," which is rich in haemocyanin. This blue oxygen transport protein is analogous to haemoglobin in humans and many other vertebrates.

P. charcoti had the highest concentration of haemocyanin in its blood - at least 40 percent more - compared to the other studied species - that's amongst the highest levels reported for any octopod.

The researchers suspect that such high blood pigment concentrations may be compensating for the haemocyanin's poor ability to release oxygen to tissues while in cold environments, and could help to ensure sufficient oxygen supply.

The Antarctic octopus' haemocyanin was also found to shuttle oxygen between gills and tissue far better when temperatures were above freezing (10 C), which may help this particular species combat our warming world.

It could also explain the lifestyle of this animal, which tends to hang out in (relatively) warmer, shallow waters and rock pools.

So hot or cold, this octopus is prepared for anything.

The findings were published in the journal Frontiers in Zoology.

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