Climate strongly influences the geographic distribution and timing of mosquito-borne disease outbreaks. Environmental temperature affects phenotypic traits of mosquitoes including vector competence for arboviruses mediated by changes in infection, extrinsic incubation period and in rates of transmission. Most experiments, however, are done at constant temperatures. In nature, mosquitoes are more likely to experience daily fluctuations in temperature. Here we compare disseminated infection (leg infection) and saliva infection of Aedes aegypti (L.) (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae) from Florida following oral exposure to an Asian genotype of chikungunya virus emergent in the Americas. We evaluated experimentally the effect of variable temperature regimens on disseminated infection and saliva infection of these Aedes species. Each of three temperature regimes had approximately the same average temperature (27-28°C), but differed in the magnitude of the diurnal temperature range (DTR). The large DTR was 8.0°C (range 23-31°C) and the small DTR was 4.0°C (range 26-30°C) which approximate ranges in different locations of Florida during July-October when risk of transmission is highest. The constant temperature was set at 27°C. Testing three geographic populations of each mosquito species, significant effects on disseminated infection were detected for an interaction between temperature regime and geographic population for both Ae. aegypti and Ae. albopictus. There were no significant treatment effects of temperature, geographic population, or temperature by geographic population interaction on saliva infection for either mosquito species. Constant temperature resulted in a higher viral load in the saliva of Ae. albopictus, but not Ae. aegypti, compared to conditions where the temperature fluctuated.

The environmental conditions experienced by parents can influence offspring phenotype along with the conditions experienced by offspring. These parental effects are clear in organisms that display parental care and are less clear in other organisms. Here, we consider effects of parental and offspring larval nutrition on offspring development time, survivorship and infection with dengue virus in Aedes aegypti, the mosquito vector of dengue, chikungunya, yellow fever and Zika. Parents were raised on either high or low larval detritus inputs with subsequent offspring being divided into two groups, one receiving high nutrients and the other low. Low nutrient females from low nutrient parents (LL) developed significantly slower than those from high nutrient parents (HL). Females from all parent by offspring nutrient treatment groups were equally likely to become infected with dengue virus at 24 h, 3 days and 14 days. After 14 days, high nutrient females from low nutrient parents (LH) had 11 times higher viral titres and more disseminated infections than high nutrient females from high nutrient parents (HH). These results suggest that carry-over environmental stress from the parental generation can influence life histories and arbovirus infection in Ae. aegypti females. We found males to be robust to the life-history parameters measured, suggesting sex-specific differences which may relate to their lower nutrient requirements for metamorphosis.

Citation: Zirbel, K. E., and B. W. Alto. 2018. Maternal and paternal nutrition in a mosquito influences offspring life histories but not infection with an arbovirus. Ecosphere 9(10):Abstract. The nutritional ecology of an organism can influence the phenotypes of its offspring, generating maternal effects (when derived from mothers) and paternal effects (when derived from fathers). Given the importance of larval nutrition in influencing adult life histories and vector competence in Aedes aegypti, we considered how maternal and paternal nutrition influences offspring. Parental generation females and males were reared on either high or low larval food and mated in four sex-by-parental diet crosses. Offspring traits measured included development time, survivorship, female size, susceptibility to infection with dengue virus, viral titer, and viral dissemination. We found evidence for both maternal and paternal effects on life history traits (with female development time contributing most to this effect), but not viral traits. These results were only evident when mothers mated with high larval food fathers and when fathers mated with high larval food mothers. Offspring from dissimilar nutrient condition parents developed more quickly than offspring from other parental crosses. Overall, results suggest that parental effects in Ae. aegypti are conditionally derived from both the maternal and paternal environment.