Sperms need to crane their necks to turn right to counteract a left-turning drive caused by the rotation of their tails, says new research, adding that the discovery can lead to better in-vitro fertilisation (IVF) and other fertility treatments

Led by Dr Vasily Kantsler from University of Warwick in Britain, the researchers discovered that all sperm tails (flagella) rotate in a counter-clockwise motion as they beat to enable them to move through and against the motion of a fluid.

The counter-clockwise motion means that sperm should only be able to move in a leftwards direction.

But the researchers observed that approximately 50 percent of the sperm observed in the research moved to the right.

Comprised of a head, mid connecting piece and the flagella, 3D motion analysis of the sperm found that they were distorting their bodies at the mid-piece to counteract the physical forces that would cause them to turn left.

The differences between the actions necessary for a sperm to turn left or right means that all could be able to turn in both directions or only one - indicating that there could be two physiologically distinct spermatozoa subpopulations.

"Analysing sperm's flagella beat in 3D, we have realised that all the cells rotate flagella anti-clockwise which would make them to turn left only," Kantsler noted.

At the same time, "we have noticed the right moving sperm also have a right bent in the mid-piece section of the flagella providing a force, which would counteract the left-turning", he informed.

For the study, the researchers devised an experiment to understand sperm cell behaviour under specific conditions.

By doing so, they observed "heart" shape trajectories of sperm cells in the experiments, showing the sperm turning left or right against the flow to form half of a heart shape depending on the direction they took.

The research was published in the journal Proceedings of the National Academy of Sciences.