100 Million Year Old ‘Giant’ Sperm Found in Amber

100 million years ago, two tiny, mating crustaceans (and 37 others) were forever frozen in amber. Chinese paleontologists have unearthed them and have even been able to take a look at the “giant” sperm of the male.

100 Million Year Old ‘Giant’ Sperm

After a bee or even a tiny dinosaur, it’s the turn of a giant sperm preserved in amber matrix to be discovered. Paleontologists from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences have found perfectly preserved ostracod fossils in amber in Myanmar (Burma). They then passed the fossils under an X-ray tomography machine, to generate a 3D model of the organisms frozen inside the amber in great detail. In all, the fossil samples examined contained 39 ostracods of several different species. Among them, Chinese researchers have even described a new species (moreover, a new genus): Myanmarcypris hui.

Ostracods are tiny crustaceans barely a millimeter long that swarm the world’s oceans, rivers and streams. The fossilized ostracods in question lived in the mid-Cretaceous period during the time of the dinosaurs. And two of them were in the midst of mating when they were trapped by the sweet sap of a tree.

A sperm four times the size of the sire

Chinese scientists report having successfully examined the soft parts of several ostracods trapped in amber, including their reproductive organs. Glued to each other, a male individual was even frozen as he fertilized a female.

A “giant” sperm, characteristic of these animals, was therefore visible. As clarified by researcher Renate Matzke-Karasz of the Louis-et-Maximilien University of Munich, collaborator on this study published in Proceedings of the Royal Society B – Biological Sciences, this spermatozoon is thus qualified because it could measure up to 4 , 6 times the body size of the parent maleThis would be the equivalent of a spermatozoon of about 7.30 meters in a human of 1.70 m so it requires a lot of energy to produce them! ”, Emphasizes the researcher at AFP (via GEO ).

In short, in ostracod, as in other arthropods such as common Drosophila, it is the size of the sperm that counts, not the quantity. This ostracodic sperm stuck in amber is the oldest fossilized animal sperm ever discovered.

In this case, the male ostracod has a fifth, pincer-shaped limb to grip the female. Her two hemipenis, hitherto invaginated inside her body, unfold like two emergency escape slides from a plane. The immense gametes are thus deposited in the double vagina of the female to fertilize her. “The reproductive behavior of ostracods, which is associated with dramatic morphological adaptations, has remained unchanged for at least 100 million years,” conclude the researchers behind the unusual discovery. “This is a supreme example of evolutionary stasis.”

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