Sperm Cells Swim in Circles

Nowhere to go, sperm cells from sea urchins just spin their wheels.  When packed tightly on a flat surface, the urchin sperm were found to swim in tight circles - completing a revolution every half a second. 

The superimposed image above shows a close-up of one of these circles, or vortices, which is about one-thousandth of an inch across.  In the background is a hexagonal array of vortices, each containing about 10 sperm - all swimming in a clockwise direction. 

Scientists from the Max Planck Institute have studied these arrays and found that there are no chemical signals being sent out to synchronize this ornate swimming pattern.  Instead, the alignment of vortices seems to be orchestrated by tiny currents and wakes in the fluid.

This may help explain the coordinated movements of cilia and flagella, the rodlike appendages used by cells and microorganisms to propel themselves.

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-- LiveScience Staff

Credit: Ingmar Riedel and Jonathan Howard, Max Planck Institute