The discovery was made in a female ostracod that died shortly after mating and was “buried” in a drop of resin.
An international team of paleontologists discovered giant sperm cells in a 100 million-year-old female ostracod preserved in amber in Myanmar’s Kachin province.
The animal probably mated just before it was buried in tree resin. The article was published in the Proceedings of the Royal Society.
Ostracods have been around for 500 million years and are found in oceans and freshwater rivers and lakes.
Oldest sperm cells
This is the oldest fossil in which sperm cells have been conclusively identified. Also, it belongs to a previously unknown species of crustacean that has been named Myanmarcypris hui.
Because of the pairs of calcareous valves that form its carapace, whose shape resembles that of a mussel shell, scientists were able to confirm that the animal was an ostracod.
Other ostracods have also been found and analyzed using 3D computerized X-ray reconstructions.
The images revealed details of their internal organs, limbs, and reproductive organs.
“The finds gave us an extremely rare opportunity to learn more about the evolution of these organs,” said geobiologist Renate Matzke-Karasz of Ludwig-Maximilians-Universitaet (LMU) in Munich, Germany.
The findings bring new insights into evolutionary specialization. Males of most animal species produce small sperm cells in large quantities.
A few animals, including types of fruit flies – and, of course, ostracods – have chosen a different evolutionary path.
They produce a relatively small number of gigantic sperm cells, with tails several times longer than the animal that produces them.
Previously, the oldest ostracod sperm that had been found was 17 million years old.
The fact that these animals have already developed giant sperm cells 100 million years ago implies that this reproductive strategy can really be successful in the long run.