Sex peptide receptor is not required for refractoriness to remating or induction of egg laying in Aedes aegypti

Across diverse insect taxa, the behavior and physiology of females dramatically changes after mating-processes largely triggered by the transfer of seminal proteins from their mates. In the vinegar fly Drosophila melanogaster, the seminal protein sex peptide (SP) decreases the likelihood of female flies remating and causes additional behavioral and physiological changes that promote fertility including increasing egg production. Although SP is only found in the Drosophila genus, its receptor, sex peptide receptor (SPR), is the widely conserved myoinhibitory peptide (MIP) receptor. To test the functional role of SPR in mediating postmating responses in a non-Drosophila dipteran, we generated 2 independent Spr-knockout alleles in the yellow fever mosquito, Aedes aegypti. Although SPR is needed for postmating responses in Drosophila and the cotton bollworm Helicoverpa armigera, Spr mutant Ae. aegypti show completely normal postmating decreases in remating propensity and increases in egg laying. In addition, injection of synthetic SP or accessory gland homogenate from D. melanogaster into virgin female mosquitoes did not elicit these postmating responses. Our results demonstrate that Spr is not required for these canonical postmating responses in Ae. aegypti, indicating that other, as yet unknown, signaling pathways are likely responsible for these behavioral switches in this disease vector.

Rescuing the Inhibitory Effect of the Salivary Gland Hypertrophy Virus of Musca domestica on Mating Behavior

Infection with salivary gland hypertrophy virus (MdSGHV) of Musca domestica prevents female flies from accepting copulation attempts by healthy or virus-infected males. This study focused on supplemental hormonal rescue therapy for mating behavior in virus-infected female house flies. The inhibitory effect of the virus on mating behavior in females injected with MdSGHV was reversed by hormonal therapy in the form of octopamine injections, topical application of methoprene, or both therapies combined along with 20-hydroxyecdysone. Infected females whose mating responsiveness had been restored continued to have other viral pathologies associated with infection such as hypertrophy of the salivary glands and a lack of ovarian development.

Virgin Caenorhabditis remanei females are attracted to a coital pheromone released by con-specific copulating males

The gonochoristic soil nematode Caenorhabditis remanei strictly requires copulation for species propagation. Males of this species are sexually promiscuous with females of other species; therefore, we asked in this study whether virgin C. remanei females display evidence of mate choice. We digitally recorded and measured the locomotor behaviors of one or more virgin females in the presence of a single male on a 5 mm diameter mating lawn. We observed that initially only the male modifies his locomotor trajectory to another animal on the mating lawn; the virgin females showed no locomotor bias toward the mate-searching male. However, once a male started to copulate, females in the vicinity altered their movement trajectories toward the copulating couple. Newly inseminated females are refractive to the coital signal, but partially regain their attraction to copulating males after 24 h. We found only copulating males with an intact gonad can attract females, and that the coital signal can be broadcasted at least 1.5 mm through the air. Unlike males, which are also attracted to hetero-specific females, virgin C. remanei females will only crawl toward a copulating con-specific male. We suggest that Caenorhabditis females use the coital signal as a pheromone to identify a vigorous male of their own species.

Duration and dose-dependency of female sexual receptivity responses to seminal fluid proteins in Aedes albopictus and Ae. aegypti mosquitoes

Male mosquitoes transfer seminal fluid proteins (hereafter 'SFPs') during mating. These proteins can have profound effects on female behavior in the yellow fever mosquito Aedes aegypti and the Asian tiger mosquito Aedes albopictus. SFPs are thought to be responsible for female refractoriness to mating in both species. However, only limited information is available about the duration of induced refractoriness or the quantity of SFPs required to be effective in Ae. albopictus. Here, we tested the duration of the effect of SFPs on female refractory behavior for both Aedes species. Additionally, we determined the lowest SFP dose required to induce female refractory behavior in Ae. aegypti. Virgin females were injected intra-thoracically with doses ranging from 0.25 to 0.008 equivalents of one male's SFP amount. Our results demonstrate high sensitivity of female Ae. aegypti and Ae. albopictus to SFPs of their own species, with the majority of females becoming refractory at doses ≥ 0.031 male-equivalents after injection into the hemocoel. This effect was long-lasting in both species; none of the injected females were inseminated when presented with males of their own species 30 to 34 days post-injection, whereas most saline-injected control females mated at this time point. These results will aid future work to characterize individual SFPs involved in post-mating refractoriness in these two species. Moreover, they show that as is the situation in the mosquito Anopheles gambiae, and unlike Drosophila melanogaster, sperm are not required for the maintenance of a sexual refractoriness response in Ae. aegypti and Ae. albopictus.

Insect seminal fluid proteins: identification and function

Seminal fluid proteins (SFPs) produced in reproductive tract tissues of male insects and transferred to females during mating induce numerous physiological and behavioral postmating changes in females. These changes include decreasing receptivity to remating; affecting sperm storage parameters; increasing egg production; and modulating sperm competition, feeding behaviors, and mating plug formation. In addition, SFPs also have antimicrobial functions and induce expression of antimicrobial peptides in at least some insects. Here, we review recent identification of insect SFPs and discuss the multiple roles these proteins play in the postmating processes of female insects.