Researchers discovered a 17 million-year-old giant sperm that came from ancient shrimp.
The sperm is believed to be longer than the shrimp's body, and remained coiled up in its sexual organs before release, a University of New South Wales news release reported.
"These are the oldest [fossilized] sperm ever found in the geological record," Professor Mike Archer, of the UNSW School of Biological, Earth and Environmental Sciences, said in the news release.
The freshwater crustaceans are called ostracods, they were discovered at the Riversleigh World Heritage Fossil Site.
"The Riversleigh fossil deposits in remote northwestern Queensland have been the site of the discovery of many extraordinary prehistoric Australian animals, such as giant, toothed platypuses and flesh-eating kangaroos. So we have become used to delightfully unexpected surprises in what turns up there," Archer said. "But the discovery of fossil sperm, complete with sperm nuclei, was totally unexpected. It now makes us wonder what other types of extraordinary preservation await discovery in these deposits."
The sexual organs of the fossils were well-preserved and contained giant sperm cells. The sperm itself held the nuclei that once contained the shrimp's DNA.
The Zenker organs ("chitinous-muscular pumps used to transfer the giant sperm to the female") were also extremely well-preserved.
"About 17 million years ago, Bitesantennary Site was a cave in the middle of a vast biologically diverse rainforest. Tiny ostracods thrived in a pool of water in the cave that was continually enriched by the droppings of thousands of bats," Archer said.
The bat's fecal matter would have created high phosphorous levels in the water, mineralizing the shrimp's soft tissue.
"This amazing discovery at Riversleigh is echoed by a few examples of soft-tissue preservation in fossil bat-rich deposits in France. So the key to eternal preservation of soft tissues may indeed be some magic ingredient in bat droppings," Associate Professor Suzanne Hand said in the news release.
