Sperm forms groups like Tour de France pelotons

Scientists have shown that some sperm form groups like Tour de France pelotons in order to boost their chances of success in getting to their goal first. The proposition is that the reason why they do it is the same reason why cyclists do it in this most celebrated of road races.

Bull sperm forms groups like Tour de France pelotons
Bull sperm forms groups like Tour de France pelotons. Image: Eurek Alert!

So, what has this got to do with animals? Well, not a lot except that the researchers carried out their research on bull sperm which is considered to be a relatively good model to that of humans’.

They call it ‘sperm clustering’ and it has been seen in several mammals and there is “evidence” that it also occurs in people but the reason why it happens has been a mystery. I find it a little surprising that it was a mystery because I would have thought that there is only one reason; to improve the success rate.

It looks like competitiveness begins at a very young age. The research was carried out by Chih-Kuan from North Carolina A&T State University. He thought that the clustering simply provided an aerodynamic advantage to the sperm as he watched the sperm freely leave and then re-join groups as they travelled down a simulated female reproductive tract.

He said: “This may resemble the peloton formation in biking although the fluid mechanics for sperm is drastically different”.

However, he noticed that there was no speed advantage for the sperm that had formed “pelotons”. He said: “Unexpectedly, we found that the swimming speeds of sperm in clusters were not faster than the speed of individual swimming sperm. So, what is the advantage?

He proposed that the clusters offer a navigational and endurance advantage. He checked out how the sperm responded to different flow speeds. Without a flow the clustered sperm was more able to travel in a straight path. With a flow the clustered sperm are better able to resist being swept away.

The issue that remains is whether the observations of bull sperm can be replicated in humans. Allan Pacey, Prof of Andrology at the University of Sheffield, said that the study was interesting, but he would want to see a further investigation on human sperm.

And he was concerned that a laboratory experiment might not be able to replicate what happens in real life. He said: “Whether it has significance for how babies are born, I’m not totally sure.”

Tung believes that his research may be able to help explain unexplained infertility and also in selecting the best sperm for IVF.

There is also the ultimate question about working in a group. One individual in a group is going to reach the goal first and therefore the group only gets in so far. At the end of the day, it comes down to one individual, but they appear to work together so far and then alone.

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Post Category: Bulls