World’s oldest sperm may have come from a leechlike worm
B. Bomfleur et al/Biology Letters 2015
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.
Sperm are short-lived and fragile, so preservation happens only rarely. But cocoons may offer an untapped resource for finding soft and delicate cells, and even tiny organisms,