Male Age Influences Re-mating Incidence and Sperm Use in Females of the Dengue Vector Aedes aegypti

Abstract

Diseases transmitted by female Aedes aegypti mosquitoes are public health issues in countries in the tropics and sub-tropics. As in other insects, A. aegypti females undergo behavioral and physiological changes upon mating that principally act to facilitate the production of progeny. The primary effectors of A. aegypti female post-mating responses are male-derived seminal proteins that are transferred to females during mating. Increased male age reduces ejaculate function in numerous taxa and alters seminal protein composition in Drosophila melanogaster, but the impacts of male age on female A. aegypti post-mating responses are unknown. Here, we used “old” (21–22 days old) and “young” (4–5 days old) A. aegypti males to assess the influence of male age on oviposition, fertility, and re-mating incidence in their mates. We also examined how age influenced paternity share in females initially mated to young or old males that subsequently re-mated with a transgenic male that transferred RFP-labeled sperm and whose progeny inherited a larval-expressed GFP marker. We found that increased male age had no effect on female fecundity or fertility but significantly impacted their ability to prevent re-mating in their mates—more than half (54.5%) of the females mated to an old male re-mated, compared to 24% of females initially mated to a young male. Polyandrous A. aegypti females displayed first male precedence regardless of the age of their initial mate. However, young males were better able to compete with rival male sperm, siring significantly more progeny (77%) compared to old males (64%). Young males had significantly more sperm in their seminal vesicles than old males at the time of mating, although males of both age groups transferred similar numbers of sperm to their mates. Our results suggest that male senescence differentially impacts the induction of some post-mating changes in A. aegypti females. As the effect of age may be further exacerbated in the field, age-related declines in male ability to induce sexual refractoriness have implications for A. aegypti population control programs that release adults into the environment.

Timeless or tainted? The effects of male ageing on seminal fluid

“…For instance, older male D. melanogaster are less able to delay female remating and stimulate egg laying compared to younger males (Koppik and Fricke, 2017;Ruhmann et al, 2018;Sepil et al, 2020). Similarly in Aedes aegypti mosquitoes, older males are less able to prevent female remating (Agudelo et al, 2021). These responses are largely mediated by SFPs in D. melanogaster (Chapman et al, 2003) and the expression of functionally important SFPs declines with age (Koppik and Fricke, 2017).…”

Infection by wMel Wolbachia alters female post-mating behaviors and physiology in the dengue vector mosquito Aedes aegypti

“…for 30 min and larvae were reared at a density of 200/L in type II H2O supplemented with four (7.2-8.2 mm) Hikari Gold Cichlid food pellets (Hikari, Himeji, Japan), a feeding regimen that produces adults of similar size 48,59 . 15 N-labeled females were reared with a yeast slurry (see below).…”

“…Males and females were mass mated in an 8 L cage in a 1:1 male: female ratio (25 females per cage); although a proportion of females remate when mass mated, multiple insemination does not significantly influence fecundity 48 or total sperm stored 66 in Thai strain females. After 24 h, males were removed, and females were blood-fed on the arm of a volunteer.…”

“…aegypti female PMR are seminal fluid proteins (SFPs) 42,46,47 transferred to the female reproductive tract along with sperm during mating. Female PMRs in insects are also influenced by other factors, such as male age 48 , adult nutrition 49 , and adult microbiome composition 50,51 . wMel Wolbachia has been shown to alter female PMRs in D. melanogaster 52 , which may be due to the observed modification of SFP composition in infected males 53 .…”

Effect of delayed mating on reproductive performance and life-history parameters of dengue vector Aedes aegypti

“…Their capability for disease transmission determines the medical importance of mosquitoes. Most mosquitoes are vectors of infections caused by viruses, protists, and nematodes (Agudelo et al ., 2021). Aedes mosquitoes transmit dengue, chikungunya, yellow fever, and Zika viruses to humans.…”