Giant 17-million-year-old fossil sperm found

Giant fossilized sperm found in Australia appear as ropelike structures in the seminal vesicles of a 17-million-year-old mussel shrimp.

Renate Matzke-Karasz

Gigantic sperm have been found in 17-million-year-old fossilized mussel shrimp. The specimens, collected in Queensland, Australia, carry the oldest petrified sex cells on record.

Using high-intensity X-rays, scientists were able to identify the ancient sperm in one male and three female Heterocypris collaris species and one female Newnhamia mckenziana. While the length of the petrified sperm cannot be calculated from the specimens, modern mussel shrimp from the same class can have sperm up to 10 millimeters long even though their bodies are only a millimeter or two in size, the team notes. For comparison, human sperm is roughly .055 millimeters long.

The researchers also note that the tightly filled semen receptacles found in the female N. mckenziana specimen suggest that the animal mated right before it died. The results appear May 14 in the Proceedings of the Royal Society B.

Ashley Yeager is the associate news editor at Science News. She has worked at The Scientist, the Simons Foundation, Duke University and the W.M. Keck Observatory, and was the web producer for Science News from 2013 to 2015. She has a bachelor’s degree in journalism from the University of Tennessee, Knoxville, and a master’s degree in science writing from MIT.

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