State-of-the-art 3D microscopy reveals how human sperms swim

This news release is a revision of one originally published on July 31, 2020.

Using state-of-the-art 3D microscopy and mathematics, Dr Hermes Gadêlha from the University of Bristol, Dr Gabriel Corkidi and Dr Alberto Darszon from the Universidad Nacional Autonoma de Mexico, have reconstructed the movement of the sperm tail in 3D with high-precision.

Using a high-speed camera capable of recording over 8,000 frames in one second, and a microscope stage with a piezoelectric device to move the sample up and down at an incredibly high rate, they were able to scan the sperm swimming freely in 3D.

Human sperm roll as they swim, much like playful otters corkscrewing through water to swim forwards."

Dr Hermes Gadelha, Head, Polymaths Laboratory, Department of Engineering Mathematics, University of Bristol

Gadelha is also an expert in the mathematics of fertility. "The otter-like spinning of human sperm is however complex: the sperms' rapid and highly synchronised spinning causes the to tail rotate around the swimming direction, drilling into the fluid with helical waves."

"The centreline of the 3D tail shows travelling waves of changes in chirality, known in mathematics as perversion. This is similar to changes in spiralling direction we see in plant tendrils. We now know that these perversion waves are correlated to the spinning movement of the sperm's head."

Computer-assisted semen analysis systems in use today, both in clinics and for research, still use 2D views to look at sperm movement. We can now see that 2D projections of sperm swimming can introduce inaccuracies in how we see the tail's movement.

Novel use of 3D microscope technology combined with mathematics, may provide fresh avenues for unlocking the secrets of human sperm swimming.

"With over half of infertility caused by male factors, understanding how the human sperm tail moves is fundamental to developing future diagnostic tools to identify unhealthy sperm," adds Dr Gadelha, whose work has previously revealed the biomechanics of sperm bendiness and the precise rhythmic tendencies that characterise how a sperm moves forward.