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50-million-year-old fossil sperm discovered

World’s oldest sperm may have come from a leechlike worm

By
7:05pm, July 14, 2015
ancient sperm

ANCIENT SPERM  The elongated head and whiplike tail of one of many apparent worm sperm cells studs the wall of a 50-million-year-old cocoon. 

Worm sperm have staying power. Embedded in the wall of a fossilized cocoon, mineralized sperm from what may have been a leechlike worm have stuck around for about 50 million years.

The ancient sperm fossils are the oldest yet reported. They predate the previous record holders — amber-preserved sperm from tiny jumping insects called springtails and petrified sperm from mussel shrimps — by at least 10 million years.

Researchers discovered the cocoon-entombed worm sperm by sifting through sediments from an Antarctic island. The cells’ drill bit–shaped heads and grainy texture resemble the sperm of Branchiobdellida, a group of squiggly little worms that crawl on freshwater crayfish today.

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