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Oldest animal sperm found in 100-million-year-old female seed shrimp

A reconstruction of a female ostracod’s reproductive organ filled with sperm, suggesting it was inseminated shortly before being trapped in resin

R. Matzke-Karasz

Dozens of perfectly preserved sperm coiled up inside the reproductive tract of a 100-million-year-old female microcrustacean have been identified as the oldest animal sperm ever found.

This tiny crustacean (Myanmarcypris hui) had a sexual encounter just before getting trapped in amber that had flowed from a nearby tree, says Renate Matzke-Karasz at Ludwig Maximilians University in Munich, Germany.

The roughly 50 intact sperm cells nestled inside the organs of this newly discovered species of ostracod – small …