Researchers at the University of Gothenburg in Sweden and the University of Colorado found a teensy-weensy structure at the very end of the sperm’s tail that previously went unnoticed.
It’s not clear exactly what it does, but the team thinks it could help us understand why some little swimmers are stronger than others.
A highly effective tail is needed in order for a sperm to be able to swim and for a baby to be conceived.
The tail is a highly complex machine that consists of around a thousand different types of building blocks.
One little sperm tail has around a thousand types of building blocks that build up three sections: the mid-piece, the “propeller” and a small terminus at the tip.
In the propeller are proteins called tubulins that form long tubes (microtubules) to make up more complex structures.
Inside these microtubules is where researchers spotted a cellular structure wound into a left-handed helix.
Interactions in these proteins create the movement that sperm needs to “swim” through its environment.
It’s actually quite incredible that it can work,” said Johanna Hoog from the University of Gothenburg, who led the study.
“The movement of thousands of motorproteins has to be coordinated in the minutest of detail in order for the sperm to be able to swim,” said Johanna.
The researchers looked at the first 3D images of the very end section of a sperm tail, using cryo-electron tomography.
They spotted something never seen before inside the microtubules: spiral that stretched in from the tip of the sperm and was about a tenth of the length of the tail.
“We believe that this spiral may act as a cork inside the microtubules, preventing them from growing and shrinking as they would normally do and instead allowing the sperm’s energy to be fully focussed on swimming quickly towards the egg,” said Davide Zabeo, the lead PhD student behind the discovery.
The study was published in the journal Scientific Reports.