Thursday, November 13, 2008

Ancient Climate Change Influenced Modern Octopus Evolution

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Many of the world's deep-sea octopuses evolved from species that lived in the Southern Ocean, according to new molecular evidence. Octopuses started migrating to new ocean basins more than 30 million years ago as Antarctica cooled and large ice-sheets grew.

These huge climatic events created a 'thermohaline expressway' - a northbound flow of deep cold water, providing new habitat for the animals previously confined to the sea floor around Antarctica.

Isolated in new habitat conditions, many different species evolved. Some octopuses lost their defensive ink sacs because there was no need for the defence mechanisms in the pitch black waters more than two kilometres below the surface.

Megaleledon setebos, the closest living relative of the octopuses' common ancestor. Photo: Census of Marine Life

"It is clear from our research that climate change can have profound effects on biodiversity, with impacts even extending into habitats such as the deep oceans which you might expect would be partially protected from it. "If octopuses radiated in this way, it's likely that other fauna did so also, so we have helped explain where some of the deep-sea biodiversity comes from."

The findings form part of the first Census of Marine Life (CoML), set to be completed in late 2010. It aims to assess and explain the diversity, distribution and abundance of marine life in the oceans, past, present and future. link
The thermohaline expressway: the Southern Ocean as a centre of origin for deep-sea octopuses. 2008. J. M. Strugnell et al. Caldistics, published on-line Nov. 11, 2008