Human Sperm Don’t Wiggle, They Roll Like ‘Playful Otters’ As They Swim

Cast your mind back, if you can, to high school science lessons where we were taught all about sperm and its snake-like movements.

You remember the ones, where we were unequivocally told by our teachers that the sperm cell travelled by wiggling its tail from side to side, just as a snake would?

Well, it seems we’ve been lied to all of this time, because new research has found human sperm travels not at all like a snake would, but actually rolls around in the same way a ‘playful otter’ would. Basically, we (and all of our teachers for that matter) were wrong.

Using state-of-the-art 3D microscopy and mathematics, the new study – published in Science Advances – was able to find that the side-to-side movement of the sperm’s tail was actually an optical illusion. In reality, a sperm’s tail lashes only on one side.

Researchers would usually expect this one-sided stroke to cause the sperm to swim in a perpetual circle, but they quickly realised that human sperm had figured out a clever way around this.

Study author Hermes Gadelha – Head of the Polymaths Laboratory at the University of Bristol’s Department of Engineering Mathematics – said the sperm incorporated a rolling motion into their movement, effectively solving this problem.

Gadelha – an expert in the mathematics of fertility – said, as per CNN:

Human sperm figured out if they roll as they swim, much like playful otters corkscrewing through water, their one-sided stroke would average itself out, and they would swim forwards.

The rotation of the sperm is something that is very important. It’s something that allows the sperm to regain a symmetry and actually be able to go straight.

It could be that the rolling motion hides some subtle aspects about the health of this sperm or how well it can travel quickly… What we hope is that more scientist and fertility experts will become interested and ask, ‘OK, how does this influence infertility?’

So just how could we have been wrong all this time? According to Gadelha, we’ve all been the victims of ‘sperm deception’, with the researcher describing sperm as ‘very cheeky little creatures’.

Previously, scientists had been looking at sperm from above in their microscopes, and had undoubtedly seen them swimming by moving their tails from side to side.

Yet Gadelha said that, in order to see the ‘real beating of the tail’, they needed to ‘move with the sperm and rotate with the sperm’. He added: ‘So it’s almost like you needed to make a (camera) really tiny and stick it to the head of the sperm.’

And that’s exactly what his co-authors, Gabriel Corkidi and Alberto Darszon from the Universidad Nacional Autonoma de Mexico, did, with the pair developing a way to do just that.

When they discovered their findings, Gadelha said it was a true surprise and the team spent a further two years repeating the experiment and cross-checking the maths.

The results held, effectively reversing over 300 years of scientific assumptions – an achievement that Gadelha remains modest about, saying that while they are certainly ‘right’ this time, they could be wrong again in the future as science advances.

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