Sperm cells move very differently than expected; they do not swim, but rotate.

More than three hundred years ago, the Dutch biologist Antonie van Leeuwenhoek described how sperm move with one of the first microscopes. Sperm cells are said to move in a symmetrical pattern, with the tail wagging back and forth. However, scientists have now discovered that this is a real optical illusion. Sperm cells do not appear to ‘swim’ at all, but to rotate.

Using the most modern 3D microscopy, the researchers examined the movement of the tail of sperm cells. The team used a super fast camera that took over 55,000 photos of moving sperm cells in one second. And this revealed the real movement of sperm.

The groundbreaking study reveals that the sperm tail doesn’t swing back and forth as thought, but actually wobbles only one way. You would think that in this case, a sperm keeps spinning in the same place. But that is not the case. Sperm has found a very smart way to get ahead: rolling. “Sperm cells move in a rolling fashion, similar to playful otters moving through the water like a corkscrew,” explains researcher Hermes Gadelha. “That way they get ahead anyway.”

Watch the real movement of sperm cells in this video.

It is not surprising that we have long thought that sperm cells move in a symmetrical pattern with a swishing tail. “Studying sperm cells from above with 2D microscopes gives a distorted view,” explains Gadhela. “The rapid spin of sperm creates the illusion of a tail moving to the left and right, as Leeuwenhoek described in the 17th century.” But the newly crafted 3D images show the real way sperm progresses. “Our discovery shows that sperm have developed a swimming technique to compensate for their crooked side,” says Gadhela. “They have ingeniously solved a mathematical puzzle on a microscopic scale. They create symmetry out of asymmetry. ”

This special way of moving is very complex. “The sperm head rotates around the swimming direction at the same time as the sperm tail,” explains Gadhela. “This is known in physics as precession and is comparable to the orbits of Earth and Mars around the sun.”

Sperm quality
The results from the study are promising, especially for studying sperm quality. At the moment, doctors still use 2D images to analyze sperm. In this way they map the movement of sperm cells. But the findings from the new study suggest doctors are thus misrepresented in this way. The new discovery about how sperm cells move may offer hope for unraveling secrets of human reproduction. “Since more than half of infertility is caused by male factors, understanding the sperm tail is fundamental to developing future tools to recognize healthy sperm,” Gadhela concludes.

Did you know that …

… sperm quality is quite stable until the 34th birthday? After that, the total number of sperm cells decreases. The sperm concentration and the percentage of sperm cells with a normal form decrease after the 40th birthday. After the 45th birthday, the volume of ejaculation decreases. The chance of offspring for men older than 34 therefore decreases every year.

The researchers speak of an important breakthrough, which rigorously sweeps the generally accepted theory of the way sperm moves. “This discovery will revolutionize our understanding of sperm motility and its impact on our reproduction,” said researcher Alberto Darszon. And researcher Gabriel Corkidi agrees. “This was a great surprise,” he says. “We think our state-of-the-art 3D microscope will reveal many more hidden secrets of nature. One day this technology will hopefully become available to clinical centers. ”

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