An octopus species living in the Antarctica has a specific tragedy to survive and live in the ice-cold water. Oxygen supply to its tissues has been documented in a scientific paper published in the journal Frontiers in Zoology. The octopus is said to effectively transport oxygen in its blood via a specialised blood pigment known as haemocyanin. The researchers stated that the animal might thus be more resilient to climate change than other species of octopus and animals living in Antarctic sea.
Antarctic octopod Pareledone sp. Photo credits: Tomas Lundälv
The Antarctic Ocean constitutes otherwise-hostile living conditions, with temperatures practically reaching 0˚C. However, life still thrives there, with a diverse variety of fauna, in spite of the difficulties posed by conditions characteristic of the animals living in the cold water like lower oxygen diffusion and increased blood viscosity. It is thus harder for oxygen to be delivered to tissues. But, the ice-cold seas also have large amounts of dissolved oxygen.
The Antarctic fish, for instance, rely on the great amount of dissolved oxygen in the water that reduces their need for blood pigments like haemoglobin. On the other hand, the adaptations of blue-blooded octopods with respect to oxygen supply are not thouroughly understood by scientists. In the new study, octopods have been shown to have a different strategy. The researchers found that the blue blood pigment of octopods known as haemocyanin is different in terms of quantity to increase its overall capacity of supplying blood to their tissues.
Michael Oellermann from Alfred-Wegener-Institute, Germany, the lead author, said:
“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. The results also imply that due to improved oxygen supply by haemocyanin at higher temperatures, this octopod may be physiologically better equipped than Antarctic fishes to cope with global warming.”
Octopods have been endowed with three hearts and contractile veins. This circulation apparatus pumps the blue oxygen transport protein haemocyanin in the haemolymph. The latter was collected from the Antarctic octopod species Pareledone charcoti, which is found in abundance in the Antarctic ocean, and from two other octopod species which were obtained from warmer climates: the South-east Australian Octopus pallidus and the Mediterranean Eledone moschata.
It was discovered that Antarctic octopus Pareledone charcoti had the greatest concentration of haemocyanin in its blood: around 40 % more than the other two species, and all other octopods as well.
This finding was interpreted as the Antarctic octopus compensating for the poor ability of the pigment in question to supply enough oxygen to tissues under cold temperature conditions. The increased concentration of the haemocyanin might thus be enhancing oxygen supply.
Another feature that was found was that the pigment would shuttle oxygen between gills and tissue much better at 10°C than at 0°C. At 10°C, the Antarctic octopod’s haemocyanin could release more oxygen (76.7 % on average) than that of the other two octopods, Octopus pallidus (33.0%) and Eledone moschata (29.8%).
The researchers explained that this might allow the Antarctic octopod to tolerate hotter temperatures as well as the cold. This could constitute evidence as to how octopods can be found across a broad range of ecological niches.
This might also link to the lifestyle of the Pareledone charcoti, which is also known to dwell in warmer shallow water and rock pools. Furthermore, given the warming trend evolving at the Antarctic Peninsula, the ability of the Pareledone charcoti to tune its blood oxygen supply to a wider range of temperature as compared to other species might eventually prove to be advantageous to it. It might thus survive climate change better.