160 million years ago, ancestors of cuttlefish were already using the ink defense

Researchers have shown that ink sacs from a cephalopod that lived 160-million years ago still contain traces of the pigment melanin. That's an impressive find in its own right, but what really floored the scientists was how familiar these pigments looked.

Pictured below are the fossilized ink sacs (labeled "A" and "B"), and the traces of pigment contained therein (labeled "D" and "E," respectively). When the researchers compared the pigment structures found in the two sacs with those found in the ink of modern-day cuttlefish Sepia officinalis (labeled "C"), the researchers found they were almost identical. Cephalopods, it would seem, know how to keep a good thing going.

160 million years ago, ancestors of cuttlefish were already using the ink defense

"It's close enough that I would argue that the pigmentation in this class of animals has not evolved in 160 million years," said John Simon, one of the lead researchers on the study, in a prepared release. "The whole machinery apparently has been locked in time and passed down through succeeding generations of cuttlefish. It's a very optimized system for this animal and has been optimized for a long time."

The team's findings are relevant to a variety of paleontological fields, including emerging domains of research that rely on the analysis of ancient pigment structures to determine the color of feathers on ancient dinosaurs. Understanding what these creatures looked like — or, in the case of cephalopods, what they were capable of jettisoning from their ink sacs — can tell us a lot about how they lived.

The researchers' findings are published in the latest issue of PNAS.

Images via PNAS