Pareledone charcoti, a shallow-water species of octopus from the Antarctic, uses an unique strategy to transport oxygen in its blood, says a new study carried out by scientists from the University of Tasmania in Australia and two research institutions in Germany.
The Antarctic octopus Pareledone charcoti. Image credit: Tomas Lundälv.
The Antarctic Ocean, also called Southern Ocean, forms an extreme habitat with temperatures ranging between 28.8 and 35.6 degrees Fahrenheit (minus 1.8 to 2 degrees Celsius) all year round.
Most marine animals living under these conditions are unable to regulate their body temperature and are thus required to sustain body functions at near freezing temperatures, via numerous adjustments at the molecular, cellular or systemic level. But little is known about the adaptations employed by blue-blooded octopods to sustain oxygen supply in the cold.
Octopods have three hearts and contractile veins that pump hemolymph, which is highly enriched with the blue oxygen transport protein hemocyanin – analogous to hemoglobin in vertebrates.
To find out what makes the hemocyanin of one of these octopods – the Antarctic octopus Pareledone charcoti – so well-adapted to cold water, Dr Michael Oellermann of the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research and his colleagues collected and analyzed the hemolymph from this speices and two other octopod species collected from warmer climates – the South-east Australian Octopus pallidus and the Mediterranean Eledone moschata.
Pareledone charcoti had the highest concentration of hemocyanin in its blood – at least 40 percent more compared to the other species, and ranked amongst the highest levels reported for any octopod.
“These high blood pigment concentrations may be compensating for the hemocyanin’s poor ability to release oxygen to tissues while in cold environments, and could help to ensure sufficient oxygen supply,” Dr Oellermann and his colleagues said.
The Antarctic octopod hemocyanin was also found to shuttle oxygen between gills and tissue far better at 50 degrees Fahrenheit (10 degrees Celsius) than at 32 degrees Fahrenheit (0 degrees Celsius).
At 50 degrees Fahrenheit the Pareledone charcoti’s hemocyanin had the potential to release far more oxygen (on average 76.7 percent) than the warm-water octopods Octopus pallidus (33.0 percent) and Eledone moschata (29.8 percent).
This ability may help Pareledone charcoti tolerate warmer temperatures in addition to the cold, and may link to its life style.
The findings were published online March 11 in the journal Frontiers in Zoology.
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Michael Oellermann et al. 2015. Blue blood on ice: modulated blood oxygen transport facilitates cold compensation and eurythermy in an Antarctic octopod. Frontiers in Zoology 12:6; doi: 10.1186/s12983-015-0097-x
