We Misunderstood How Sperm Swims For 340 Years, Here's The Truth

Every male mammal carries sperm for reproduction. In order to fertilize an egg, human sperm has to swim a distance equivalent to the height of Mount Everest if it were human size. To swim forward, sperm cells wiggle their tails to propel themselves. During intercourse, most of the sperm, about 50 million cells, cannot reach the egg. But only one sperm cell is enough to fertilize an egg.

In 1677, we learnt about sperm cells, but it took us another 200 years to figure out how the human forms. At the time, the preformationists believed that sperm cells contained miniature humans, and the egg cells only provided shelter for the human to grow.

However, the 1700s witnessed the surfacing of the idea of epigenesist. Those who supported this idea argued that a child is produced by both the male and female. Later in the 18th century, this idea was confirmed.

Though we have known much more about sperm now than before, there’s still something we have misunderstood for a long time.

In the 1600s, Antonie Philips van Leeuwenhoek, a Dutch businessman and an autodidact scientist, got interested in lenses. He then became the first one to observe microorganisms and considered the father of microbiology. Initially, he called microorganisms “animalcule,” which is translated into "tiny animal" in English. He was also the first person to observe muscle fibers, bacteria, and blood flow.

Over the next 200 years, there weren’t any lenses better than the one created by Leeuwenhoek. And the perception of how sperm cells swim like eels in the water hasn’t been much different from his description. That changes now.

Using the latest 3D microscopy technology, researchers successfully reconstructed the sperm cell tail’s movements. Before now, this was a challenge due to its tiny size and dexterity.

The tail of the sperm cell, or flagella, can whip about 20 times per second, but when looking at it with super-fast shutter cameras (55,000 fps), the researchers spotted something off.

It turns out that the flagella crooked, meaning their movements in the liquid should make them spin around in circles, but sperm cells have a genius way to reduce this effect. While waddling around, they just roll, pretty much like an otter does a corkscrew motion in the water.

Computer-aided sperm analysis systems used in research and clinical settings still use 2D viewing methods, so they have this illusion and fail to detect if sperm cells move asymmetrically, this impacts fertility.

Over 50% of the infertility cases have a relation to the male population, so it’s important to increase our understanding of sperm.

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