When we imagine the way in which human sperm move, we imagine the movement of a small fish, a tadpole or even a snake. According to a recent study, spermatozoids swim like otters by turning on themselves.
Until today and for more than three centuries, human beings were totally wrong about the nature of sperm movement. In 1677, the Dutch scholar Antoni van Leeuwenhoek published works (PDF in English / 5 pages) on the subject. The person concerned indicated that when the spermatozoa swim in search of the egg to fertilize, they whip their tails like snakes or eels in the water.
And yet, this is completely false according to a study published in the journal Science Advances on July 31, 2020. Researchers from the University of Bristol (UK) and the National Autonomous University of Mexico (Mexico) brought a completely different conclusion . For scientists, this is an error whose persistence can be explained very simply. The fact is that the "snake-like" tail movement has fooled science since it is an optical illusion.
In a model visible at the end of the article, the leaders of the study explain that the 2D view and from above via a microscope is misleading. What Antoni van Leeuwenhoek and thousands of other researchers saw is a perfectly symmetrical movement male gametes. And yet, the latter actually have an asymmetrical shape, similar to that of a corkscrew. However, the fact is that this form would in no way allow them to perform the kind of movement that was attributed to them until today! Thanks to 3D microscopy, scientists have been able to confirm that spermatozoa manage to compensate their balance by rotating on themselves like "playful otters". In other words, sperm are not swimmers but rather "rollers".
“ The rotation of the otter-shaped human sperm is however complex:its head rotates at the same time as its tail rotates in the direction of swimming. This is known in physics as precession, much like when the orbits of Earth and Mars precede around the sun" reads a press release reporting on the study.
Finally, the question that could be asked is the following:what are these searches really for? According to the leaders of the study, better understanding the way in which male gametes move could allow us to have a more precise idea of the effects of movement on fertilization. Moreover, the researchers felt that there was still a lot of misunderstanding regarding the human body.
Here is the model published as part of the study:
