November 10, 2008—It may be the most adorable deep-sea invertebrate this side of Eddie McBlobbules, but this juvenile octopus, shown in a photo released Sunday, isn't actually smiling.

"It's quite cute," but the squinting eyes are just skin folds (the real eyes are off to the sides), and the smile is "just sort of color patterns," said biologist Jan Strugnell of Queen's University in Belfast, Northern Ireland.

Strugnell is lead author of a new study showing that this shallow-water octopus species, Megaleledone setebos, is the evolutionary originator of many of the world's deep-sea octopuses.

The biologist compared genes of octopuses—including new species, such as Pareledone turqueti (photo)—that had been pulled from Antarctic waters.

By incorporating fossil information, she was able to date the original divergence from Megaleledone at about 30 million years ago, when an increase in sea ice fueled a deep, oxygen-rich current.

That current allowed the ancestral octopus to go deeper into the ocean. Over time the octopus evolved into multiple species, each adapted to its environment, according to the study, to be published tomorrow in the journal Cladistics.

For example Megaleledone's deep-sea descendants have no ink sacs—ink camouflage being of limited use in complete darkness.

More on this discovery and others made possible by the Census of Marine Life project >>

—Ted Chamberlain