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Images: Scientists Find a New Twist in How Squids Swim

Squids use a small funnel?below the eye in this photo?to shoot jets of water that propel the animal forward through moving water. Engineers had assumed that squids took advantage of a hydrodynamic phenomenon known as vortex rings to move themselves efficiently, until Woods Hole-based researchers observed jets coming out of the funnel.

In order to measure the fluid flow around swimming squid and fish, Erik Anderson built a robotic camera-laser system that could measure motion within millimeters of the squid?s skin. Laser light shines on the animal and on the microscopic, silver-coated beads in the water, while high-resolution digital cameras capture the flow from different angles and fields of view.

Biomechanics researcher Erik Anderson observes an eel swimming in a specially designed flume he developed with Senior Scientist Mark Grosenbaugh of the WHOI Applied Ocean Physics and Engineering Department. Water flows through the plexiglass test tank at speeds up to 1.6 meters per second (3.6 miles per hour). The green light is a laser used to detect the edge of swimming animals (including squid) and microscopic, silver-coated beads flowing in the water.

These plots depict water velocities in the wake of a swimming squid. The colors represent the speed of the water (reds are high speed; blues, low), and the arrows show flow direction. The squid (arms shown in white) is swimming at 25 centimeters per second (1 foot per second). The long red streak of fast moving water is the column-like jet of the squid emitted from the nozzle under its arms. Water velocities in the jet approach 50 centimeters per second--twice as fast as the squid is swimming.