Male Infertility – How Sperm Movement Has Fooled Scientists
The fertilisation of almost every living organism on our planet depends on Sperm. Did you know that the distance a human sperm travels, to find an egg, is almost equivalent to climbing Mount Everest?! And out of the millions of sperm that travel, only one single sperm will eventually fertilise the egg.
For hundreds of years, it has been believed that human sperm “swim” by wiggling their tails to move the fluid and swim forward. This theory has now been proved wrong and it seems that human sperm have been “fooling” scientists for generations!
One of the first microscopes was developed by Antonie van Leeuwenhoek in the 17th century. The lens allowed the magnification of objects to 270 times. Strangely, an improved lens was not manufactured for over 200 years.
Leeuwenhoek was one of the first explorers of the microscopic world and when he discovered sperm, he described it as a “living animalcule” with a “tail, which, when swimming, lashes with a snakelike movement, like eels in water”.
With the use of extremely modern 3D microscopy technology, Dr. Hermes Gadelha from the University of Bristol, Dr. Gabriel Corkidi, and Dr. Alberto Darszon from the Universidad Nacional Autonoma de Mexico have been able to observe and correct our presumption of the rapid movement of the sperm tail. The study of the movement was rather difficult since the tail measures only half the breadth of a hair and they move so fast, The movement of the tail of the sperm is capable, in one second, of beating over 20 swimming strokes!!
However, with the 3D technology, scanning the sperm tail while swimming freely led to a rather amazing fact – the sperm tail wiggles on only one side which would mean that the one-sided stroke would lead to it swimming only in circles! However, the sperm has conquered this hurdle by rolling as they swim – as the sperm rolls, the one-sided stroke evens out and they are able to move forward. As the tail rotates, the sperm body spins at the same time, like a top around its axis, thus causing precession and movement.
The illusion caused by the sperm’s rapid spinning, while viewed through a 2D microscope, leads to an appearance of a side-to-side movement.
Now that this has been clarified with the 3D technology, it proves that sperm have been able to overcome the one-sided wiggle and by that, have created symmetry out of asymmetry. This is an important issue which may affect fertility.
The characteristics of a semen sample and the sperm are measured by the routine and most basic investigation, a Semen Analysis, normally done manually with a light microscope. However, even CASA (Computer-Assisted Semen Analysis) systems still use 2D views of the movement of sperm, both in clinics and for research, so there is still an illusion of symmetry with the semen analysis.
Now, with the 3D microscopy technology, this latest discovery may have an impact on the cause of male infertility. Understanding the movement of the human sperm tail could be one of the major diagnostic tools of the future to identify unhealthy sperm and, as scientific advances in this area increase with the development of microscopic technologies, so will the chance of improving fertility.