Ostracods are tiny crustaceans that have existed for almost 500 million years. Also known as seed shrimp, these organisms are covered by a hard shell that tends to fossilize easily, allowing scientists to piece together a detailed picture of their exceptionally long history.
While hard parts of animals like bones and shells generally preserve well, softer components like organs and fluids are much more rare, making it difficult to learn about aspects of life that we can’t see. But a team of scientists recently uncovered a cache of ancient ostracods with many of these soft physical elements intact.
These ostracods were found in a village in Myanmar, nestled within a small chunk of amber estimated to be 100 million years old. Of the 39 ostracods present in the amber, 31 belong to a new species, which the team named Myanmarcypris hui.
To peer inside these tiny organisms without damaging them, the team left the ostracods inside the amber and X-rayed them at a high resolution. When they analyzed the images of an adult female M. hui, they found something shocking: coiled threads of sperm.
The previous record holder for oldest ostracod sperm was a 17 million year old individual from Australia, while the oldest sperm ever discovered was from a 50 million year old worm. But this 100 million year old sperm surpasses both records.
And this sperm isn’t just old — it's giant. The team found that when uncoiled, it would have been almost half as long as the animal itself. These megasperm would have had an advantage as they raced through the long coils to the female’s eggs, a strategy that is also found in fruit flies.
Finding such ancient, giant sperm shows just how successful this reproductive strategy has been over the last 100 million years. It also provides a snapshot of a singular moment deep in the past — one that occurred in a world that looked very different from our own, and is still occurring among ostracods today.