Don’t Miss Out on the Latest Updates.
Subscribe to Our Newsletter Today!
Human sperm travels a long distance to reach an ovulated egg for fertilization. During intercourse, sperm gets deposited into the vagina, from where it travels through the cervix and into the uterus to finally reach the awaiting egg in the fallopian tube. While the total distance it covers may only be 10 centimeters, considering the sperm's relatively small size, it is equivalent to running a marathon. They complete this long journey simply by wiggling their tail.
Antonie van Leeuwenhoek, who developed one of the earliest microscopes in the 17th century, described human sperm as a "living animalcule" having a "tail, which, when swimming, lashes with a snakelike movement, like eels in the water". Even today, it is commonly believed that sperm swim forward by wiggling their tail from side-to-side. But a new study, published in the journal Science Advances, has refuted this universally accepted perception of sperm mobility and claims that sperm don't swim, but they spin.
Using state-of-the-art 3D microscopy technology, the team of researchers from the UK and Mexico, reconstructed the rapid movement of the sperm tail in 3D. The sperm tail only measures half a hair's breadth and it moves so fast that it is difficult to study its mobility.
For the new study, the research team uses a super-fast camera capable of recording over 55,000 pictures in one second that was mounted in a fast oscillating stage to move the sample up and down at an incredibly high rate. This enabled them to effectively scan the sperm tail while swimming freely in 3D.
They were surprised to discover that the sperm tail is, in fact, wonky and only wiggles on one side. This means we've been wrong about how sperm swim for the last 350 years.
While the sperm's one-sided stroke makes it rotate in circles, sperm have found a clever way to adapt and swim forwards. "They roll as they swim, much like playful otters corkscrewing through the water. In this way, the wonky one-sided stroke evens out allowing them to move forwards," the researchers explained.
"The sperms' rapid and highly synchronized spinning causes an illusion when seen from above with 2D microscopes - the tail appears to have a side-to-side symmetric movement, like eels in the water, as described by Leeuwenhoek in the 17th century," IANS quoted study author Hermes Gadelha from the University of Bristol in the UK as saying.
"Our discovery shows that sperm has developed a swimming technique to compensate for their lop-sidedness and in doing so they have also ingeniously solved a mathematical puzzle: by creating symmetry out of asymmetry," Gadelha added.
According to the researchers, the sperm body spins at the same time that the tail rotates around the swimming direction. Sperm "drills" into the fluid like a spinning top by rotating around itself whilst its tilted axis rotates around the center they said.
This is known in physics as precession, much like the precession of the equinoxes in our planet.
The researchers hope that this discovery may help unlock the secrets of human reproduction and support future diagnostic tools for identifying unhealthy sperm and improving fertility.