Direct and indirect effects of predation and parasitism on the Anopheles gambiae mosquito

Abstract

Background: A good understanding of mosquito ecology is imperative for integrated vector control of malaria. In breeding sites, Anopheles larvae are concurrently exposed to predators and parasites. However, to our knowledge, there is no study on combined effects of predators and parasites on development and survival of larvae and their carry-over effects on adult survivorship and susceptibility to further parasite infection. Methods:This study focused on effects of the nymphs of the dragonfly Pantala flavescens and the parasitic fungus Beauveria bassiana on Anopheles gambiae, to determine: predation efficacy of nymphs against An. gambiae larvae; development rate of An. gambiae larvae in the presence of one, two or four constrained nymphs; efficacy of B. bassiana against An. gambiae larvae at doses of 3, 6 and 12 mg; and survival of adult mosquitoes exposed to B. bassiana, following pre-exposure to a constrained predator and/or parasite at the larval stage. The experiments consisted of survival bioassays quantified as pupation day, or dead larvae and/or adults.Results: Nymphs had an average predation efficacy of 88.3% (95% CI: 87.5-89.1) at 24 hours, against An. gambiae larvae. The presence of one or two nymphs reduced development time of larvae by 0.65 and 0.35 days, respectively. However, development time of larvae exposed to four nymphs was similar to the control larvae. Larvae exposed to 3, 6 and 12 mg of B. bassiana were 2.0, 2.5 and 3.5 times more likely to die, respectively, compared to control larvae. Adults not pre-exposed, those pre-exposed to predator, parasite, or both were 45.8, 67.4, 50.9 and 112.0 times more likely to die, respectively, compared to control that were unexposed to predator or parasite, at larval and adult stage. Conclusions:This study shows that both predator and parasite can reduce larval population of An. gambiae, and presence of predator cues decreases development time in breeding sites, as well as, increases the susceptibility of emerging adult to fungus. Predator and parasite both have an additive effect on survival of adults exposed to B. bassiana. Field studies are required for an in-depth understanding of predator and parasite influence on mosquito development time, survival and susceptibility in nature.

Predatory and competitive interaction in Anopheles gambiae sensu lato larval breeding habitats in selected villages of central Uganda

“…Compared to temporary habitats, permanent breeding habitats tend to support higher densities of predator and competitor taxa [ 21 ]. Predation on larvae by aquatic insect predators affects larval development, impacts the adult sex ratio at emergence and subsequently influences the adult life-history traits such as body size, fecundity and longevity [ 22 , 23 ]. The presence of predators and competitors in aquatic larval habitats lowers their chances of being chosen as oviposition sites by female An.…”

Wing size and parity as markers of cohort demography for potential Anopheles (Culicidae: Diptera) malaria vectors in the Republic of Korea

“…was not related to habitat disturbance or predation. However, Ong'wen et al (2020) found that the presence of a predator (dragonfly nymphs) decreases development time of An. gambiae larvae, as well as increasing the susceptibility of emerging adults to a parasite (fungus).…”

Mosquito responses to lethal and nonlethal effects of predation and an insect growth regulator

“…Similarly, studies on predator–prey interactions in mosquitoes have shown both reductions in prey density as well as changes in important aspects of prey, such as development time, size, fecundity, and pathogen infection, that may alter the risk of disease transmission (Roux et al 2015, Huang et al 2017, Roux and Robert 2019, Ong’wen et al 2020, Alomar et al 2020). For instance, the introduction of predatory mosquito Toxorhynchites moctezuma larvae resulted in reduction of larval population density of Aedes aegypti (Tikasingh and Eustace 1992).…”