Archive for June, 2010
SquidMania
Dr. Sacks’s favorite creatures are cephalopods: squids, octopus, cuttlefish, nautilus–all those mollusks that have neurons not only in their heads (cephalo-) but in their feet (-pods) as well. They’re very smart. Dr. Sacks says, ”Cuttlefish have enormous eyes, they are curious and, I think, even affectionate. One cannot help feeling that they have individuality and consciousness, and the basis of an inner life. Cephalopods can learn by observation, as higher mammals do. They are richly endowed with nerve cells: an octopus has 300 million or more neurons, about half in its cerebral ganglia, and the rest distributed among its tentacles. I like cephalopods because they are so removed from us and yet, in some fundamental ways, so like us. They are my favorite aliens.”
Not to mention, they like to swim by jet propulsion (Dr. Sacks has to rely on flippers). And they like to surround themselves with vast clouds of ink (Dr. Sacks was sometimes called “Inky” as a boy, since he was fond of a fountain pen even then). They have quite sophisticated eyes, and their blood is blue. They are better at cloaking themselves than a Klingon warbird. We could go on and on.
So if we were in charge, June would be National Cephalopod Month. You could watch the amazing NOVA program “Kings of Camouflage,” featuring Roger Hanlon of the Marine Biology Lab in Woods Hole.
Or you could learn more about octopuses in a gorgeously illustrated new book, Octopus: The Ocean’s Intelligent Invertebrate by Jennifer Mather, Roland Anderson, and James Wood.
Of course, you should do so while wearing your Welcome Squid Overlords t-shirt. We’re not quite sure how many humans are on the planet these days, but there are even more squid. Just sayin.’
P.S.: Whew! Squid fossil mystery solved at last.
P.P.S.: For a spectacular meta-list of cephalopods online, check here.
Footnote of the Month: June 2010
“Stereo Sue,” a chapter in The Mind’s Eye, is about Sue Barry, a neurobiologist who suddenly acquires stereopsis, and true three-dimensional vision, in her fifties. After a lifetime of inferring depth by other monocular cues such as perspective and motion parallax, Sue is stunned by the beauty of her new sense of 3-D space and depth. While most of the the chapter is about Sue’s experiences, Dr. Sacks also points out how stereo vision is important for animals:
Stereopsis, as a biological strategy, is crucial to a diverse array of animals. Predators, in general, have forward-facing eyes, with much overlap of the two visual fields and, presumably, stereoscopic vision; prey animals, by contrast, tend to have eyes at the sides of their heads, which gives them panoramic vision, helping them spot danger even if it comes from behind. An astonishing strategy is found in cuttlefish, whose wide-set eyes normally permit a large degree of panoramic vision but can be rotated forward by a special muscular mechanism when the animal is about to attack, giving it the binocular vision it needs for shooting out its tentacles with deadly aim.
In primates like ourselves, forward-facing eyes have other functions. The huge, close-set eyes of lemurs serve to clarify the complexity of dark, dense close-up foliage, which, if the head is kept still, is almost impossible to sort out without stereoscopic vision—and in a jungle full of illusion and deceit, stereopsis is indispensable in breaking camouflage. On the more exuberant side, aerial acrobats like gibbons might find it very difficult to swing from branch to branch without the special powers conferred by stereoscopy. A one-eyed gibbon might not fare too well—and the same might be true of a one-eyed lemur or cuttlefish.
From The Mind’s Eye, Chapter 5.