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Thursday, 8 May 2014

Octopus Einstein

Measuring the minds of other creatures is a perplexing problem. One yardstick scientists use is brain size, since humans have big brains. But size doesn’t always match smarts. As is well known in electronics, anything can be miniaturized. Small brain size was the evidence once used to argue that birds were stupid—before some birds were proven intelligent enough to compose music, invent dance steps, ask questions, and do mathematics.

Octopuses have the largest brains of any invertebrate. On average the size of a walnut—as big as the brain of the famous African gray parrot, Alex, who learned to use more than one hundred spoken words meaningfully. That’s proportionally bigger than the brains of most of the largest dinosaurs.
 
For its color palette, the octopus uses three layers of three different types of cells near the skin’s surface. The deepest layer passively reflects background light. The topmost may contain the colors yellow, red, brown, and black. The middle layer shows an array of glittering blues, greens, and golds. But how does an octopus decide what animal to mimic, what colors to turn? Scientists have no idea, especially given that octopuses are likely colorblind.


But new evidence suggests a breathtaking possibility. Woods Hole Marine Biological Laboratory and University of Washington researchers found that the skin of the cuttlefish Sepia officinalis, a color-changing cousin of octopuses, contains gene sequences usually expressed only in the light-sensing retina of the eye. In other words, cephalopods—octopuses, cuttlefish, and squid—may be able to see with their skin.

So why is the octopus so intelligent? What is its mind for? The current scientific thinking is that the event driving the octopus toward intelligence was the loss of the ancestral shell. Losing the shell freed the octopus for mobility. Now they didn’t need to wait for food to find them; they could hunt like tigers. And while most octopuses love crab best, they hunt and eat dozens of other species—each of which demands a different hunting strategy. Each animal you hunt may demand a different skill set: Will you camouflage yourself for a stalk-and-ambush attack? Shoot through the sea for a fast chase? Or crawl out of the water to capture escaping prey?

Losing the protective shell was a trade-off. Just about anything big enough to eat an octopus will do so. Each species of predator also demands a different evasion strategy—from flashing warning coloration if your attacker is vulnerable to venom, to changing color and shape to camouflage, to fortifying the door to your home with rocks.