World's Oldest Sperm, And Maybe The Largest, Found Inside Fossilized Shrimp

While exploring a fossil cave inside Australia’s vast Riversleigh World Heritage Fossil Site in northern Queensland, paleontologists found something more “exciting” than bat remains.

The limestone inside the cave contained the soft tissue of an ancient muscle shrimp known as an ostracod. And what type of soft tissue is, you ask? Well, it happens to be tissue containing a perfectly preserved, 17-million-year old giant sperm.

“These are the oldest fossilized sperm ever found in the geological record,” Michael Archer, a onetime director of the Australian Museum who co-authored a study published Wednesday in the Proceedings of the Royal Society B told the Washington Post. “It’s staggering.”

The shrimp really is a shrimp – measuring only about 1 millimeter long. But by proportion the bodily fluid inside it is enormous. If it were to be uncoiled, the shrimp sperm “can reach up to ten times the body length of its producer,” Science Daily reported.

The researchers found four female shrimp and one male, who apparently became one lucky guy shortly before their lives came to a close and they began to rapidly fossilize.

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The new study theorizes that mussel shrimp probably began deploying giant sperm for more than 140 million years.

"No one knows why ostracods have giant sperm or how they originated, and the new evidence that they have been around for millions of years only adds to the mystery," micropaleontologist David Horne of Britain's Queen Mary University of London told USA Today.

These mussel shrimp aren’t the only tiny creatures to produce super-sized sperm. Some flies and other insects also produce sperm that is far bigger than their bodies.

This is also not the first time that scientists have found fossils of creature in some state of post-coital bliss.

In something right out of Jurassic Park, researchers have found sperm packets from insects preserved in amber from the Early Cretaceous period, and insects frozen in the act of mating are preserved in amber dating back 130 million years. Scientists have also come across the preserved bodies of male and female turtles – with the male turtle’s tail looking like it was ready for action.

And while this “ancient sex with gargantuan sperm” may not be the most pleasant thing to think about, scientists say that it is fascinating and could help them understand these strange creatures better.

“It doesn’t conjure up the nicest image, does it?” Archer said. “But at the end of the day, it’s fascinating.”

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