nature.net
February 2007
Of Arms and the Brain
By Robert Anderson
Last summer my son and I went snorkeling in the chilly waters off Catalina Island, along the California coast. As we swam above a kelp forest swaying with the surf, we spotted fish by the hundreds. Then my son pointed excitedly toward a yellowish-brown creature jetting along the rocky bottom. Sliding over some dark green stones, it instantly changed to a matching color, vanishing from sight as if by magic. This master of camouflage, I later learned, was a California two-spot octopus.
Members of the Cephalopoda, the class that includes cuttlefishes, nautiluses, and squids, along with octopuses, can change appearance in seconds. You can watch marine biologist Roger T. Hanlon’s clip of the action. To see a species that does more than just disappear into the background, see the Indonesian mimic octopus clip. That takes you to a short video of an octopus that mimics any one of three toxic species that occur in its native waters: a lionfish, a sea snake, or a sole.
The Cephalopod Page, maintained by James B. Wood, a research scientist at the Bermuda Institute of Ocean Sciences in St. George’s, is a good place to discover what features besides camouflage make cephalopods so fascinating. Near the top of the page, click on the “Lessons” section to select among the modules on cephalopod biology. There you’ll find out about the mechanics of quick color changes and the physiology of the cephalopod eye, which is similar to our own. Or click “Cephalopod Articles” on the menu at the top to find more detailed (and marvelous) information: for example, “20,000 Tentacles Under the Sea: Cephalopods in Cinema,” by the marine biologist Roland C. Anderson of the Seattle Aquarium, examines the creatures’ horror-movie appeal and lists their film credits.
Their fearsome reputation is not entirely unfounded. Recently Japanese investigators, filming nearly 3,000 feet, caught on camera an adult giant squid, with an arm span (tip to tip) of twenty-six feet, in the act of hunting—the first images of an adult both alive and in the deep (go to the BBC’s article Live giant squid caught on camera and click on the video near the upper right).
Still, their monster image notwithstanding, cephalopods are an important source of the world’s protein, as well as a favorite animal in medical research. At the Web page of the National Resource Center for Cephalopods at the University of Texas Medical Branch, click on “Cephalopod Literature and Infor-mation Resources” and then on “The Peerless Squid” for an overview of how the study of the squid’s giant nerve cell, with its readily manipulated pencil-lead-thick axon, has led to key discoveries in neuroscience.
Of all the invertebrates, the giant Pacific octopus is often cited as the most intelligent. David Scheel, a marine biologist at Alaska Pacific University in Anchorage, on The Giant Octopus Web Page, notes that they can reach several hundred pounds and span nearly two dozen feet from arm tip to arm tip. PBS’s Nature series has the most startling video clip of all—an excerpt from “The Octopus Show.” The keepers at the Seattle Aquarium kept finding the remains of four-foot-long sharks in their tank for big fish. Nighttime filming caught the culprit red-armed: the giant Pacific octopus they had innocently placed in the enclosure was snacking on the so-called “top” predator.
Robert Anderson is a freelance science writer living in Los Angeles.
Copyright © Natural History Magazine, Inc., 2007