Magazine article Oceanus

A New Twist on How Squid Swim

Magazine article Oceanus

A New Twist on How Squid Swim

Article excerpt

Erik Anderson was vexed by scientific papers he read in his first year of graduate studies in the MIT/WHOI Joint Program. Two groups of engineers asserted that squid propelled themselves by creating vortex rings--that is, by forcing fluid out of their pipe-shaped funnels so that the jets roll up into structures resembling smoke rings.

Anderson, who had studied squid while working on a master's degree, begged to differ. Together with his Ph.D. thesis advisor, Mark Grosenbaugh of the WHOI Department of Applied Ocean Physics and Engineering, Anderson set up a series of experiments to check the theories against some observational evidence.

Laboratory experiments, using cylindrical pipes in still water, showed that vortex rings provide efficient propulsion, so engineers presumed squid took advantage of them.

"They suggested this without looking closely at a squid swimming," Anderson said. "This failure to consider the real biological system led them to wrong conclusions. We knew something else was going on."

Anderson and Grosenbaugh put live squid (Loligo pealei) into a flume they built in WHOPs Rinehart Coastal Research Laboratory. They added microscopic, silver-coated beads to the water, shined laser light on the squid and beads, and imaged the motion of their experimental ocean. The technique allowed them to visualize and measure the jet emitted from the squid and the water streaming by.

Analyzing the flow, Anderson saw that squid propel themselves with prolonged column-shaped jets, like the full-blast flow from a garden hose. …

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