You're looking at the world's oldest sperm. At 17 million years old, it's not quite as lively as it once was — but it still took scientists some serious investigation to identify it.
The samples in which it resides were discovered at the Riversleigh World Heritage Fossil Site by a team including University of New South Wales researchers back in 1988. They were known be shrimp fossils, but little more was thought of them. Then, recently, the samples found themselves in the hands of John Neil, a specialist ostracod — that's fancy for shrimp — researcher at La Trobe University, who realised they may contain something a little more... ballsy.
Following microscopic analysis, Neil found that the samples in fact contained the preserved internal organs of the shrimp — including their sexual parts. Hopefully, he peered further, only to find giant sperm cells within the organ, and sperm nuclei within them. Mike Archer, one of the researchers, explains:
"These are the oldest fossilised sperm ever found in the geological record. [T]he discovery of fossil sperm, complete with sperm nuclei, was totally unexpected. It now makes us wonder what other types of extraordinary preservation await discovery."
The study is published in the journal Proceedings of the Royal Society B. Also found in the sample were the Zenker organs: muscular pumps used to transfer the giant sperm to the female. In fact, careful analysis has shown that the sperm within the shrimp would have been, when uncoiled, almost the same length as the shrimps themselves — about 1.3mm. Just imagine that scaled up to human size. [ Proceedings of the Royal Society B via UNSW via Verge]