How human sperm really swim
Progress Educational Trust
11 August 2020
Research using high-precision 3D microscopy has overturned 350-year-old observations about how sperm swim.
Antoine van Leeuwenhoek, a pioneer of 2D microscopy described human sperm cells swimming by lashing their tails from side to side 'like that of a snake or an eel swimming in water'. However, a recent study has shown this was due to an optical illusion. Researchers from Bristol and Mexico discovered that human sperm cells actually move by lashing their tails to one side.
'Our new research using 3D microscopy shows that we have all been victims of a sperm deception,' said study author Dr Hermes Gadelha, senior lecturer in applied mathematics and data modelling at Bristol University. 'If you want to see the real beating of the tail, you need to move with the sperm and rotate with the sperm. So it's almost like you needed to make a (camera) really tiny and stick it to the head of the sperm.'
The researchers scanned two different groups of freely swimming human sperm cells using a 3D microscope and a high-speed camera. The two groups consisted of sperm cells that swam (i) near to and (ii) far from the microscope coverslip. Their results, published in the journal Science Advances, revealed that sperm heads spin in one direction whilst the sperm tail rotates in the opposite direction. This one-sided spin should cause the sperm cells to swim in circles, however:
'Human sperm figured out if they roll as they swim... their one-sided stroke would average itself out, and they would swim forwards,' said Dr Gadelha.
These new findings demonstrate the power of using 3D microscopy technology to study cells. This approach could be used to study the dynamics of the human sperm tail further in efforts to better understand the process of human fertilisation and reproduction, which could lead to the development of improved diagnostic tools to distinguish between healthy and unhealthy sperm cells.
'This was an incredible surprise, and we believe our state-of-the-art 3D microscope will unveil many more hidden secrets in nature. One day this technology will become available to clinical centres, ' said co-author Dr Gabriel Corkidi from the National Autonomous University of Mexico in Mexico City.
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David Mortimer PhD
17 August 2020
Sperm have been wiggling and rolling since at least the 1970s
A recent claim that "the postulation of symmetry [in sperm motility] has not changed since Leeuwenhoek’s first observations in the 17th century" 350 years ago , which has garnered extensive attention in the lay press and media, is, put simply, false. While the mathematical approach taken by the authors is interesting, there is broad knowledge amongst spermatologists, supported by extensive evidence in the literature, of flagellar beat asymmetry and a three-dimensional swimming path in spermatozoa.
In 1973 I was taught as an undergraduate zoology student at the University of Bristol by Tom Thompson that sperm swim in a more-or-less helical path, although the mechanism for that was not yet understood. Tom was my first mentor, and also told me about Reynolds number, something that has framed my perspective of sperm biology throughout my career. Under the low Reynolds number of the sperm-in-an-aqueous-environment system, there is a fundamental requirement for asymmetry in order to achieve progression .
I believe that it was David Phillips who first proposed – in the early 1970s – that sperm swim in a rolling pattern , and this was followed by a paper from Anne Swan (then Denehy) which included the running title "How sperm wiggle and roll" . Further work on the "twisted plane" concept underlying the helical paths came from David Woolley , who later used two-colour microscopy to reconstruct three-dimensional flagellar waves . Then at Spermatology 1982 David Phillips showed movies of swimming sperm from which the audience had to judge which way the sperm were rotating as they swam .
A possible structural basis for the origin of a twisted plane wave, at least in human sperm, due to asymmetry in the order of termination of the other dense fibres, was proposed by Catherine Serres of Georges David / Pierre Jouannet's group in Paris , I included a figure illustrating their findings in my recent review on sperm ultrastructure and function .
Finally, there has been a number of papers in recent years using new imaging techniques that visualize the 3D swimming pattern of sperm [e.g. 10].
In conclusion, it would seem incumbent upon engineers, physicists and mathematicians who investigate sperm motility to read more of the older cell biology sperm literature to avoid making inaccurate claims of precedence. We all stand on the shoulders of giants, and need to respect those who went before. True discoverers and innovators must be respected and remembered, and I believe this is a professional responsibility of both authors and reviewers.
David Mortimer PhD
 Gadêlha H et al. Human sperm uses asymmetric and anisotropic flagellar controls to regulate swimming symmetry and cell steering. Sci Adv 6:eaba5168, 2020.
 Purcell EM. Life at low Reynolds number. Am J Phys 45:3-11, 1977.
 Phillips DM. Comparative analysis of mammalian sperm motility. J Cell Biol 53: 561-573, 1972.
 Denehy MA et al. Rotational and oscillatory components of the tailwave in ram spermatozoa. Biol Reprod 13: 289-297, 1975.
 Woolley DM. Interpretation of the pattern of sperm tail movements. In: Fawcett DW & Bedford JM (eds) The Spermatozoon. Maturation, Motility, Surface Properties and Comparative Aspects, Urban & Schwarzenberg, Baltimore, 1979.
 Woolley DM. A method for determining the three-dimensional form of active flagella, using two-colour darkground illumination. J Microsc 121:241-244 1981.
 Phillips DM. The direction of rolling in mammalian spermatozoa. In: Andre J (ed) The Sperm Cell. Fertilizing Power, Surface Properties, Motility, Nucleus and Acrosome, Evolutionary Aspects. Martinus Nijhoff, The Hague 1983.
 Serres C et al. Ultrastructural morphometry of the human sperm flagellum with a stereological analysis of the lengths of the dense fibres. Biol Cell 49:153–162, 1983.
 Mortimer D. The functional anatomy of the human spermatozoon: relating ultrastructure and function. Mol Hum Reprod 24: 257-294, 2018.
 Su et al. Sperm trajectories form chiral ribbons. Sci Rep 3: 1664, 2013, doi: 10.1038/srep01664.