CHAMPAIGN, Ill. -- While scientists aboard Sunburst, the Smithsonian Institution's ocean-going vessel, stalk the elusive giant squid in its natural deep-water habitat, researchers combing the California coast say they have unlocked a possible reason for a squid's ability to avoid capture.
In a study comparing the nervous systems of the squid and octopus (cephalopods) with a variety of snail-like sea slugs (gastropods), it was found that cephalopods have more rapid-acting electrical firing systems than their more sluggish molluskan kin. The adaptation enables the squid's high-speed, jet-propelled swimming behavior and may partly explain the intelligence shown by octopuses.
The key element of the findings, say University of Illinois and Stanford University scientists, involves sodium channels proteins in nerve-cell membranes that generate the electrical impulses that buzz along axons in the brain during decision-making and along nerve fibers for driving muscular responses. The more rapidly sodium channels open and close, the faster electrical activity is turned on and off, and the faster impulses can be transmitted, much as with a high-speed modem.
That sodium channels in motor neurons used in jet-propelled swimming are faster than those of other types of nerve cells in squids was reported in 1992 by William F. Gilly, a marine neurobiologist at Stanford. In the 1970s, other researchers noted that sodium-channel activity seemed unusually slow in some snails. In 1993, Gilly's group cloned a squid gene, suspecting it was a fast-type squid sodium channel; its structure was similar to that found in vertebrates, including humans.
Acting on a hunch, Rhanor Gillette, a U. of I. physiology professor,
worked with Gilly and Stanford doctoral student Matthew McFarlane to use
new technology to re-examine the fast-slow sodium channel
Contact: Jim Barlow, Life Sciences Editor
University of Illinois at Urbana-Champaign