Can Sperm Slither?

By ScienceGenetics (Own work) [CC BY-SA 3.0 ( or GFDL (

Scientists at the University of Toronto have discovered something in sperm that was previously unknown. Sperm can swim in a slithering motion when they are close to the wall of the environment they are in.


A slithering sperm cell looks like a snake wiggling across a desert. The head of a sperm will point in one direction while the long tail swishes back and forth behind it. These motions will propel the sperm in a straight line and all of these actions occur in a two-dimensional plane.

This is a direct contradiction to other known methods of sperm locomotion. Scientists have named these actions “typical,” “helical,” hyper-helical,”hyper-activated,” and “chiral ribbons.” These sperms swimming motions require the tail of the cell to move in three dimensions, using a corkscrew type motion.

Researchers from the University of Toronto discovered the existence of sperm being able to slither by studying semen from bulls and human beings. The team of scientists were led by graduate student, Reza Nosrati, and it involved using an imaging technique called total internal reflection fluorescence microscopy. This method let them measure the movements of sperm about one-trillionth of a meter away from the bottom of a glass petri dish.

It was found that the closer to edge of the dish the sperm were, the more likely they were to swim in a slithering motion. The viscosity of human sperm was a factor as well, the more viscous the environment, the more likely the cells were to swim with a slithering motion

The sperm of humans and bulls swam in straighter lines when they slithered. However, slithering seems to be more beneficial and useful in human sperm than in bull sperm. When bull sperm swam in a slithering motion, it resulted in 50% slower speeds than when they used another type of motion for movement. However, the sperm of humans swims 50% faster when in slithering mode.

It probably isn’t due to a coincidence, because when human sperm moved through the fallopian tubes, the passages become narrow and increased speed and motility would be needed and it could force sperm to travel closer to the edge of the tubes. Only the sperm that gets to the egg first is able to fertilize it.

Bull sperm do not have to fight with narrow passageways. Because the fallopian tubes of a cow are much larger, bull sperm have a better chance for fertilizing the egg when they can swim faster in a bigger space where three dimensional motion is more effective.

Results of the Study and Future Research

One day, it’s possible the findings of this study could lead to better fertility treatments. The study could help doctors recognize the strongest sperm with the hardiest DNA. David Sinton, senior study author, stated he was inspired to study the locomotion of sperm after him and his wife required fertility treatments to help them conceive.


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