AntonievanLeeuwenhoek used the earliest microscopic observation to describe that human sperm has a "tail, which meanders in the water and moves like a snake when swimming". After more than 300 years, scientists finally found that this is an illusion.
Dr. HermesGadelha of Bristol University, Dr. GabrielCorkidi of National Autonomous University of Mexico and Dr. AlbertoDarszon took the lead in reconstructing the real movement of sperm tail by using the most advanced 3D microscope and mathematical technology.
Using a high-speed camera that can record more than 55,000 frames per second and a microscope stage with piezoelectric devices, they can scan sperm freely by moving the sample up and down at a very high speed.
This breakthrough research published in the journal Science Progress reveals that the tail of sperm actually only swings to one side. Nevertheless, sperm found a clever way to adapt and swim forward.
Dr. Gader Ha, from Bristol University School of Medicine, said: "Human sperm will roll when swimming, just like otters playing in the water."
"When viewed from above with a 2D microscope, the rapid and highly synchronous rotation of sperm will produce hallucinations-the tail seems to move symmetrically, as described by Levin Hooke in the17th century. However, our findings show that sperm have a swimming technique to compensate for their skewness. In this way, it skillfully solves the mathematical problem at the micro-scale: creating symmetry through asymmetry, "said Dr. Gadelha.
"However, the rotation of human sperm like an otter is very complicated: the sperm head rotates and the sperm tail rotates around the swimming direction."
At present, the computer-aided semen analysis system used in clinic and research still uses 2D view to observe sperm movement. Therefore, just like Levin Hooke's first microscope, they are still prone to this symmetrical illusion when evaluating semen quality. This discovery, combined with the novel application of 3D microscope technology and mathematics, may provide new hope for unlocking the secrets of human reproduction.
Dr Gadelha added: "since more than half of infertility is caused by male factors, understanding the tail of human sperm is the basis for developing future diagnostic tools to identify unhealthy sperm. This discovery will completely change our understanding of sperm motility and its impact on natural fertilization. "
Source of information: howhumansperreallyswim: new research challenges-old assumptions
Original source: Hermes Delhaetal. Symmetrical and anisotropic flagella control library of human sperm. Scientific progress, 2020 doi:10.126/sciadv.aba5168.