Video Credit: polymaths-lab.com
SPINNERS, NOT SWIMMERS
“The sperm is not even swimming, the sperm is drilling into the fluid,” Gadêlha said.
The rotation of the head and tail are actually two separate movements controlled by two different cellular mechanisms (asymmetric and anisotropic): when they combine, the result is something like a rotating drill. During 360-degree rotation, the lateral movement of the tail is balanced, increasing forward propulsion.
In technical terms, how the sperm moves is called precession, which means that it rotates around an axis, but that axis of rotation is changing (which ensures final symmetry). A simpler example to explain is a spinning top, which moves circularly across the floor while rotating at its tip. In other words, the sperm’s tail moves like a top that cancels the one-sided swimming movement in an ingenious corkscrew movement: symmetry is achieved through asymmetry, allowing the human sperm to swim forward.
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