‘Every sperm for itself’ is a myth, new research finds

Most sperm action happens once inside the female reproductive system – which, while a very challenging place to observe, is where sperm thrive. Because of this, several persistent misconceptions have emerged, such as the notion that sperm competition is a constant aspect of reproduction. Now, new research proves that sperm embrace teamwork.

Chih-kuan Tung, a physicist at North Carolina Agricultural and Technical State University, and colleagues noticed this clustering in their laboratory in a previous study they had completed in 2017.

From this study, the group knew that bull sperm, similar to human sperm, formed clusters, but also that those clusters couldn’t swim faster than individuals. Therefore, there was no apparent advantage as to why this clustering was happening.

In a statement to New Scientist, Tung explains, “in biology, when [cells and structures] do something, they should probably get something out of it … So that became the question we were asking ourselves: what are these sperm getting out of it? “

100 million fresh bull sperm, a silicone tube, and ‘melted cheese’-like fluid

To answer the enigma, the researchers put 100 million fresh bull sperm into a silicone tube filled with fluid that mimicked the cervical and uterine mucous of cows. According to Tung, this fluid had the consistency of melted cheese. The scientists then used a syringe pump to create two speeds of flow.

The scientists discovered that the clustered sperm swam in a straighter line than the individual sperm when there was no flow.

Additionally, individual sperm could not move upstream in an intermediate flow, but the clusters could. When the flow was high, the clustered sperm were much more effective at pushing through the approaching current than individual sperm, which typically got carried away by the heavy stream.


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