Characterization of the post-mating responses of Drosophila hydei, a species that lacks Sex-Peptide.

Sex Peptide (SP) induces many of the most studied female post-mating responses (PMRs) in Drosophila melanogaster but has been lost multiple times in the Drosophila genus. We decided to explore the PMRs of Drosophila hydei, a species without SP. Our work shows that the PMRs in D. hydei are somewhat different than those found in D. melanogaster and may be the consequence of a selection for producing a reduced number of extremely long sperm. D. hydei females lack the substantial post-mating increase in egg production found in D. melanogaster, mostly displaying only a brief induction in the laying of stored eggs. Mated females do not show a reduction in lifespan that has been linked to changes in metabolism and egg production. To further explore the reproductive biology of this species, we performed sperm competition experiments that suggest that D. hydei females may select sperm based on characteristics linked to changes in seminal fluid proteins. This was further investigated by examining the structure of the seminal fluid-producing accessory glands and the egg laying PMRs in different Drosophila species. Finally, video-based monitoring of D. hydei females was used to uncover novel changes in circadian rhythm and light preference in mated females.