Why fruit fly sperm are giant

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Mating Drosophila fruit flies (Image: Stefan Lüpold, UZH)

The fruit fly Drosophila bifurca is only a few millimeters in size but produces sperm that are almost six centimeters long. An international team of researchers lead by the University of Zurich now provides the first conclusive explanation for the evolution of such giant sperm. On the one hand, larger sperm are able to displace their smaller competitors from the female reproductive tract, generating a competitive advantage in fertilizing the eggs. On the other hand, female promiscuity increases the success of fertilization by larger males, which can afford to produce more of the longer sperm than their smaller counterparts. UZH News Release