Tiny Marine Crustacean Uses Power Stroke in Cold Water
Posted on April 2, 2013
The copepod, a tiny marine crustacean, switches to a power stroke in cold water to survive. Copepods are found in nearly every aquatic environment on Earth and are one of the most abundant animals on Earth. They are eaten by just about everything in the water. Scientists used high-speed digital 3-D holography techniques to film the little crustaceans switching from overlapping strokes to big power strokes in cold water.
Copepod larvae swim about using three pairs of appendages that act like three pairs of oars. The copepods' "oars" do not move in complete synchrony like those in a rowboat. In warmer, less viscous water conditions, the three pairs of appendages stroke in an overlapping, wave-like motion. In cold, thick water, copepods switch to using one big power stroke at a time. The strokes with different pairs of appendages do not overlap. This results in the copepod taking one step back for every two steps forward, but it does enable them to escape predators.
These clips of copepod larva were taken with high speed video at 3000 frames per second, and are played back at 100 frames per second in the clips, so these are slow motion at 1/30 speed. Take a look:
The research was published here in PNAS.
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