In terms of reproduction, human sperm have to swim a long distance to find the egg by wiggling tail, moving fluid to swim forward. Though over 50 million sperms will fail to reach the eggs, it only takes one single sperm to fertilize an egg. But after almost 350 years, since the discovery of sperm in 1677, new research claimed that experts have been wrong about how the sperms swim.
A team of researchers from the UK and Mexico used 3D microscopic technology to mathematically reconstruct the rapid movement of the sperm tail in 3D. The experts found that a sperm's tail measures half a hair's breadth and the sperm is also fast.
The researchers noted that as their tail's whip-like movement is capable of beating more than 20 swimming-strokes in one second or less, they used a camera capable of recording more than 55,000 pictures in a second. It was mounted in a way so that it could move up and down at a high speed. As per the experts, it helped them scan the sperm tail effectively in 3D.
Later, the researchers became surprised to find that the sperm tail is wonky and only wiggles on one side. This finding indicates that sperm's one-sided stroke would have it swim in circles, but they have found a way to adapt and swim forward. As per the researchers, sperms roll as they swim, much like the way otters corkscrew in the water, allowing it to move forward.
The Illusion
Sperm's rapid and synchronized spinning creates an illusion when seen from above with 2D microscopes that the tails have a side-to-side movement. But the new discovery has shown that sperm has developed a swimming method to compensate for the wonky one-sided stroke.
The sperm spins at the same time when their tail rotates around the swimming direction. The lead author of the study, published in the journal Science Advances, Hermes Gadêlha, Senior Lecturer in Applied Mathematics and Data Modelling, University of Bristol said, "Sperm 'drills' into the fluid like a spinning top by rotating around itself whilst its tilted axis rotates around the center. This is known in physics as precession, much like the precession of the equinoxes in our planet."
The Hope in Future
The development of the 3D microscopy technology will change the way scientists analyze semen in the future, said Gadêlha. With the help of this technology combined with mathematics, the latest discovery may provide an opportunity for revealing the unknown facts about human reproduction.
As over half of infertility cases are caused by male factors, understanding the human sperm tail is extremely required for future diagnostic tools and identifying unhealthy sperm, and improving fertility rate.
