Deep octopus has shallow ancestor

BBC News is reporting that extant deep-sea octopi invaded from the shallow Antarctic as the global conveyor belt spun up 30 million years ago, delivering oxygen rich waters to the anoxic abyss. The downwelling paved the way for a shallow Antarctic common ancestor to radiate into the deep sea. That species remains alive today, thirty million years later. Megaleledone setebos (pictured) is an Antarctic endemic.

Antarctic Bottom Water forms as shallow freshwater crystallizes to ice, leaving dense hypersaline water behind. This water sinks and spreads across the entire abyssal plains of the Southern Hemisphere, even north along the slope of South America and into the Caribbean Sea. AABW is partly responsible for the re-oxygenation below the oxygen minimum zone (~700 m) in the North Pacific. Now its a vector for evolution and radiation in the deep sea, too.

I might be worried about this because global overturning is potentially threatened by rising sea surface temperatures, as so eloquently depicted by the film Day After Tomorrow. The deep octopus story is contrary to the evolutionary trajectory of shallow stylasterid hydrocorals, which invaded the shallows from the deep sea, where they originated.

These new results are another notch in the belt for the Census of Marine Life, aka the best thing to happen to marine biology in fifty years. From the BBC news article it looks like CoML is gearing up for a second round of marine census in years 2010 to 2020. Hopefully together we will be bringing dozens more freaky new species to a home theater near you.

The World Conference on Marine Biodiversity will host 700 delegates this week in Valencia, Spain. Much more on this here on the wire and here at CoML. - PJE

Reference:

Strugnell, JM, AD Rogers, PA Prodo, MA Collins & AL Allcock. 2008. The thermohaline expressway: the Southern Ocean as a centre of origin for deep-sea octopuses. Cladistics 24: 1-8.