New York: Scientists have discovered the world's oldest known animal sperm cells - dating to a whopping 50 million years ago - embedded within the walls of a fossilized cocoon in Antarctica.
Researchers believe that an ancient relative of worms or leeches likely created the cocoon while mating, and released its sperm inside. The sperm became trapped in the cocoon before the enclosure's walls hardened, the researchers said. The cocoon likely preserved the sperm cells while fossilizing over millions of years, they said.
"Our discovery of sperm in a leech cocoon from Antarctica is the oldest record of fossil animal sperm and one of only a tiny number of such fossils in the geological record," said lead author Benjamin Bomfleur, a paleontologist at the Swedish
Museum of Natural History.
Researchers found the cocoon while sieving sediments for small vertebrate remains during an expedition in Antarctica, 'Live Science' reported. They then used a scanning electron microscope to examine the fossil's surface, and the particles on it, at very high magnifications.
Researchers also used high-power X-rays from a particle accelerator in Switzerland to image the cocoon's internal structure. These analyses showed that the cocoon held bacteria and sperm cells, Bomfleur said.
However, the early Eocene specimen did not hold entire sperm cells, just pieces of them. "All we found are fragments of the drill-bit-shaped 'head regions,' ornamented midpiece regions that presumably contain the nuclei, and very long, whiplike tails, some attached to the midpiece regions," Bomfleur added.
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