The Tale of an Antarctica Octopus
Dr Jan Strugnell is the lead author of a new international study that reveals how the genes of a fairly sedentary Antarctic octopus provide a clue to the risk of sea-level rise if world temperatures keep climbing. Published in the journal Molecular Ecology and reported on Britain’s Natural Environment Research Council Planet Earth website, the study found that the genetic make up of Turquet’s octopus was startlingly similar in both the Weddell and Ross Seas. The only problem is that the two seas are on opposite sides of Antarctica and have no direct sea link. So what happened?
As these two bodies of water are some 10,000 kilometers apart, on opposite sides of Antarctica separated by the West Antarctic Ice Sheet, researchers think such strong genetic similarity is only possible if there had been a previous collapse of the ice sheet, maybe as recently as 200,000 years ago.
The Ross Sea is a deep bay of the Southern Ocean in Antarctica between Victoria Land and Marie Byrd Land. The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula.
This suggests that scientists’ concerns about the state of today’s ice sheet could well be justified. Planet Earth says while a previous study, in 2010, provided the first evidence of a trans-Antarctic seaway connecting the Ross and Weddell Seas, the findings by Dr Strugnell’s team are the first genetic evidence of such a connection.
A former Rhodes Scholar, Dr Strugnell has made world headlines with the results of her research into the evolution of deep-sea octopuses. She says modern molecular studies have revealed that the Southern Ocean is teeming with a huge diversity of previously unknown marine life.
Her work revealed that all octopuses found in deep oceans world-wide originated in the waters around the South Pole about 33 million years ago. They spread into other oceans around 15 million years ago, as the Antarctic cooled and eventually froze over. There are around 300 recognized octopus species, which is over one-third of the total number of known cephalopod species.
As a result long ago, there was an outflow from Antarctica of cold, nutrient-rich water with high levels of salt and oxygen, creating a north-bound freeway along which octopuses travelled to their new habitats.
"We think that if octopuses colonized the deep sea by this route, it’s very likely that other organisms did so as well," says Dr Strugnell.
She says her research also demonstrates that climate change can have profound effects on biodiversity, with impacts extending into habitats as remote as our deep oceans.
For further information see Octopus.
Megaleledone Octopus image via La Trobe University.