Capable of darting at exceptional speeds modulating their colors in a flash, squid straddle contrary roles as aggressive hunters and apprehensive hunted.
I was scuba diving off the Caribbean island of Bonaire when I looked up and suddenly found myself face-to-face with a row of squid, lined up before me like a squadron of jet fighters. Each about a foot long, they hovered in the water motionless, save for the slight undulations of their winglike fins. As we stared at one another, the iridescent colors of their bodies varied in a seemingly endless array of beautiful patterns. At times, those patterns so perfectly matched the rays of sunlight filtering down from above that they momentarily seemed to disappear.
I gazed at them transfixed for a while, then moved in closer. Instantly they glided the same distance in the opposite direction. Again and again I tried to close the gap between us, but they would have none of it.
Finally I stopped, and as I did, I suddenly felt that they were watching me with the same sort of attitude with which I was watching them. Not as predator watches prey or as prey observes predator, but as one curious animal regards another. Something seemed to be going on behind those intelligent pairs of eyes.
With one shot left in my camera, I was determined to capture them on film. Slowly I raised the lens and took aim. That was it--I had pushed them too far. In a flash, they released a half-dozen jets of ink and zoomed away at warp speed, never to be seen again. The experience was brief but nonetheless unforgettable.
Ancient and diverse
Like octopuses and cuttlefish, squid are cephalopods--a class of creatures that has been around for about 500 million years. Early cephalopods were burdened with a hard outer shell that made it all nut impossible to speed through the water. But as their predators adapted and became swifter, new forms of cephalopods emerged whose outer shell gave way to an internal stiffening structure. This design has allowed squid to often escape even the fastest of predators.
Today squid are as diverse as they are fascinating. "Just because you've seen one type of squid doesn't mean that you've seen them all," notes Roger Hanlon, coauthor of Cephalopod Behavior (Cambridge University Press 1996) and director of the Marine Resources Center at the Marine Biological Laboratory in Woods Hole, Massachusetts.
There are roughly 200 different species of squid, with sizes ranging from under an inch to over 60 feet. Some jet through the water tail-first; others drift along head-down. Some spend their lives in relatively shallow water; others stay offshore, migrating vertically from incredible depths during the day to near surface at night. Their habitats range from Arctic waters to the tropics.
The diversity of squid parallels that of their predators--for squid are prey for almost all fishes and marine mammals. That being said, the basic squid design is fairly uniform. The soft, muscular body (called the mantle) is tubular in shape, with the head at one end and caudal fins at the other. From the head project eight arms and two long feeding tentacles. The creature's large eyes seem remarkably humanlike, which may explain why divers who encounter squid often feel that they are being watched.
To capture prey, squid shoot out their tentacles and, using clusters of suckers (or in some species, hooks), grab the intended meal and pull it within reach if the arms. The arms, also equipped with suckers, then wrestle it into a parrotlike beak that tears it up and feeds it into an esophagus running right through the brain--a brain that's the largest of any invertebrate--and down into the stomach.
Just beneath its head, the squid has a funnel from which it can squirt out jets of ink. This ink is a handy defense to confuse a predator during the squid's escape.
One of the unique aspects …