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Thursday, June 14, 2012

What Does the Octopus Tell us About Climate Change?

Originally posted June 12, 2012
Written by Deb Anderson

Octopuses help us understand our world - past, present, and future - yet another reason to love these fascinating cephalopods! Check out this interesting interview with geneticist, Jan Strugnell, to learn what the octopus can tell us about the planet.

AN ANTARCTIC octopus has given scientists a clue to the risk of catastrophic sea-level rise if world temperatures keep climbing. La Trobe University geneticist Jan Strugnell and an international team analysed the genes of the Turquet's octopus, which lives in the Southern Ocean, as part of the first Census of Antarctic Marine Life (a 10-year project involving about 2700 experts from 82 nations). Dr Strugnell says scientists now have the largest sample sizes ever collected from Antarctica and this finding shows their climate concerns could be justified.

What led you to study the genes of a relatively sedentary Antarctic octopus?

We were interested in investigating patterns of connectivity around Antarctica in a marine species and we wanted to try to get a picture of what the past environment was like. We wanted to see what factors have influenced the evolution of this species and if the octopus contained genetic signatures of the past environmental conditions.

Why this creature — what makes it so special?

The Turquet's octopus is an ideal choice as it presents in large populations and is found all around the Southern Ocean. This octopus also lays relatively few, large eggs — between 22 and 60 eggs, each about 20 millimetres long — and they hatch into little octopus that live on the sea floor close to their parents, ie, they don't have a planktonic larval phase like most octopus.

And this has implications for genetic research?

This means there isn't as much genetic mixing between populations as there is in a species with a planktonic phase, so each population can develop different signatures across generations if they have been separated for a long time.

Your work must involve incredible fieldwork?

Yes. I've been lucky enough to travel to the Southern Ocean twice to catch octopus — once to locations around the Antarctic Peninsula and a second time to the Amundsen Sea [in western Antarctica]. The trips are for a few months at a time. The scenery is very beautiful and the ice is surprisingly colourful.

How on earth do you keep warm?

Life on research ships is very comfortable and warm inside. Working on the deck can get pretty cold, though — and you definitely need multiple pairs of gloves to stop your fingers freezing.

This research was part of a census?

Yes. The Census of Antarctic Marine Life and the International Polar Year really facilitated sharing samples between different countries and organisations, which made this study possible.

And this study, how did you do it?

We sampled 450 individuals of Turquet's octopus from locations all around the Southern Ocean. I genotyped 10 microsatellite loci — fast-evolving population genetic markers, and I also sequenced cytochrome oxidase I — the "barcoding gene" — from each of these octopus. We used this data to look for similarities and differences in the genetic signatures of octopus sampled from populations around the Southern Ocean.

What did you discover?

We expected we would find a marked difference between octopus populations separated by large distances. However, the genetic signatures of populations in the Ross Sea and the Weddell Sea — on opposite sides of Antarctica, separated by about 10,000 kilometres — are startlingly similar.

Can you explain the significance of that?

This is an interesting finding because it supports some climate models that suggest sometime during the last 1.1 million years there has been a collapse of the West Antarctic Ice Sheet. This would have raised the global sea level by 3.3 metres to five metres, and created a seaway across West Antarctica between the Ross and Weddell seas, potentially allowing exchange of animals between these seaways. The genetic similarity we see in octopus from the Ross and Weddell seaways supports this idea of a historic seaway.

What does this tell us about the years ahead?

This has implications for the future as some scenarios of future climate change predict such a collapse during the next two centuries, which would again open this seaway and permit genetic exchange between these regions.

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