Mexican scientists discover how sperm really swims shattering centuries-old assumption

It’s been 340 years seen Anton van Leeuwenhoek watched a sperm cell for the first time. Technology back then, and the one that has been used even to our days, has allowed people to have a certain understanding of the movement of these reproduction cells although it is quite different from what can be observed.

“We have all been deceived by sperm,” sais Hermes Gadelha, chief of the Polymaths Laboratory of the Engineering Mathematics Department the University of Bristol in the UK, regarding the observations scientists have done since they are two-dimensional perspectives while the work they have performed is different because it was done with 3D microscopy.

Gadelha led the mathematical analysis of the sperm cell’s movement but also had other collaborations such as support from Mexican researchers Alberto Darszon, who led the theoretical and experimental part, and Gabriel Corkidi, who was in charge of the design of the engineering for the 4d data acquisition system.

The members of the Biotechnology Institute of the National Autonomous University of Mexico (UNAM) have studied since the mid-2000s the male gametes, a work that at a shorter stage made them win the Image of Solutions of the Year Award. Now, with their latest results, they have been able to understand that the way in which sperm cells move is different from what was thought years ago.

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3D images to understand sperm cells

Biochemist Alberto Darszon remembered in an interview with EL UNIVERSAL that these studies’ first steps were through sea urchin sperm since they are a popular model for understanding how these cells move.

“Due to technological limitations , studies had always been done in two dimensions. There was a need to develop technology to be able to do it. Every time you have a new tool to see new things, you can discover things that could not be seen before,” said the expert regarding the problems with the tools that used to be available for this kind of work.

The researcher said the new results present a different way of seeing how the tail moves, “which we will obviously have to corroborate and keep studying carefully.”

In order to perform the studies, Gabriel Corkidi comments that in terms of technology, they first used an optical telescope such as the one commonly used although he was able to expand it to visualize the three dimensions.

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“To put it simply, what we do is to make the microscope’s lense oscillate at a very hard speed so that it can capture images of the object we are seeing in a three-dimensional volume, combining it with a very fast televisión camera that can take 5,000 pictures per second,” he said.

By combining these tools, they can acquire a volume through which the reproductive cell moves, although this technology’s results are obtaining millions of data.

“Filming this cell for five seconds represents 30,000 images, hence, you can imagine the amount of information that accumulates and that has to be computationally and mathematically analyzed,” added the Mexican professor.

Regarding the complexity of the analysis of all this information, he says that in order to record five seconds of the sperm’s movement, they have to invest a lot of time, it can even take them a week; “and if we have 100 cells to analyze in our study, then they are 100 weeks of experiments plus all the years of knowledge to be able to establish these working protocols.”

Understanding the optical illusion

The sperm’s deception to which Hermes Gadelha referred is a problem of technology and observation which has been understood by modern technology.

To exemplify, Corkidi says that a subject that swims with a single arm in a pool and putting the observer at a really high point.

“Of course, if he swam with a single arm, he would not be able to do so in a linear way; it’s like a speedboat, if only one paddle was activated, it would begin spinning.

“Let’s imagine that the swimmer starts rotating on himself, on his body’s axis, and keeps swimming with one arm. If we see that movement from up top, it would seem as though he used both arms because when he is upside down, he moves the right side, and when he is spinning facing up, it will seem as if it is his left side. Of course, this is only if you watch him from enough distance so as not to see the detail of the athlete’s position.”

In an essay, the experts mention another example: “If we rode on this cell’s head as if it were a horse and hugged it, we could see that, actually, this cell’s head spins like a corkscrew and that its tail movement only moves from the middle up and not symmetrically.”

It is with this movement that Gabriel Corkidi says there is an optical illusion for the sperm cell moves its tail up to 30 times per second from the middle to the end in an asymmetrical way but since it is also spinning its body, this causes the impression of symmetry.

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Understanding infertility

Researcher Alberto Dsrszon said a sperm cell’s movement is very important for fecundation so understanding the movement of the tail will allow finding one of the reasons for fertility problems.

There are still reasons that have yet to be determined regarding infertility , so that is one of the contributions from this investigation that involves experts from different research centers.

“Nearly 9% of couples in the world have fertility problems, and from them, almost half is linked to men’s problems. From all these cases, 75% has unknown causes,” said the winner of the National Award for Sciences and Arts 2009 in the category of Physical-Mathematical and Natural Sciences.

Understanding how a sperm cell works at a molecular level gives scientists more tools to solve problems that used to have no solution since there are still properties and mechanisms from the male gamete that can be related to fertility issues.

“We know a lot, but there are many things we still ignore. Having better tools allows us to be able to solve more problems. Not only in the case of men and clinical problems but in matters of breeding and fishing for which reproduction is essential,” he adds.

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Among the plans of the Mexican scientists is improving technological tools to be able to make longer and more detailed observations.

“With our current technology, we can only watch five seconds of this kind of movement, and we want to expand it to minutes. We want to see how this cell behaves in a longer period because it is a cell that takes decisions when it swims when the female gamete is attracting it,” said Gabriel Corkidi.

By observing the sperm cell’s tail movement, the experts will obtain more accurate data that are close to reality regarding these cells of which there is still a lot left to learn.

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