Oldest Animal Sperm: 50-Million-Year-Old Cells Unearthed In Cocoon

Want to guess how old the oldest living sperm in the world is? Well just about 50 million years old, according to paleobiologist Benjamin Bomfleur.

The sperm was discovered in a fossilized cocoon that contained the ancient cells. Bomfleur and Swedish Museum of Natural History paleobiologist Thomas Mörs spotted the fragments of what appeared to be sperm when they used an electron microscope to examine the inner surface of the cocoon fossil, which had been collected by an Argentinian expedition on Seymour Island, which lies off the Antarctic Peninsula.

"Because sperm cells are so short-lived and fragile, they are vanishingly rare in the fossil record," Bomfleur noted, according to Nature.

Bomfleur then showed the discovery to Marco Ferraguti, an expert on annelid sperm via the help of radiometric dating to better assess the cocoon. They discovered that the specimen inside was at least 50 million years old.

The findings also revealed how the fossilized sperm is very similar to that of modern-day crayfish worms. However, the location from which it was found indicates that the prehistoric animal existed in a wider geographic area than its modern counterparts.

"This discovery offers an opportunity to discover a great deal about the evolutionary history of micro-organisms for which we previously had little fossil data," Bomfleur added, via the MailOnline.

However, you're probably wondering too how the sperm owner created a protective husk for an egg and sperm during the worm's reproduction phase.

"The cocoon is formed by a sticky mucus that takes several days to harden, but once it does, biological material, such as sperm, can be trapped along its walls," Bomfleur said, via The Washington Post.

Bomfleur added that while sperms themselves don't fossilize well, it can be a potential clue into the creator of certain cocoons. Furthermore, the discovery is said to encourage future researchers to look for certain structures.

"I think we might have a really interesting system here that can be sort of a hidden window to the past," said Jakob Vinther via Nature, who studies invertebrate evolution at the University of Bristol. "There could be a lot of potential hidden gems inside those cocoons."

More information regarding the findings can be seen via the journal Biology Letters.

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