Octopaminergic/tyraminergicTdc2neurons regulate biased sperm usage in femaleDrosophila melanogaster

Abstract

AbstractIn polyandrous internally fertilizing species, a multiply-mated female can use stored sperm from different males in a biased manner to fertilize her eggs. The female’s ability to assess sperm quality and compatibility is essential for her reproductive success, and represents an important aspect of postcopulatory sexual selection. InDrosophila melanogaster, previous studies demonstrated that the female nervous system plays an active role in influencing progeny paternity proportion, and suggested a role for octopaminergic/tyraminergicTdc2neurons in this process. Here, we report that inhibitingTdc2neuronal activity causes females to produce a higher-than-normal proportion of first-male progeny. This difference is not due to differences in sperm storage or release, but instead is attributable to the suppression of second-male sperm usage bias that normally occurs in control females. We further show that a subset ofTdc2neurons innervating the female reproductive tract is largely responsible for the progeny proportion phenotype that is observed whenTdc2neurons are inhibited globally. On the contrary, overactivation ofTdc2neurons does not further affect sperm storage and release or progeny proportion. These results suggest that octopaminergic/tyraminergic signaling allows a multiply-mated female to bias sperm usage, and identify a new role for the female nervous system in postcopulatory sexual selection.