Larvicidal treatment impacts the internal microbiome of mosquitoes in hurricane created larval habitat

Ephemeral aquatic habitats and their associated microbial communities (microbiomes) play important roles in the growth and development of numerous aquatic insects, including mosquitoes (Diptera). Bactericides, such as Bacillus thuringiensis isrelensis (Bti) or insect growth inhibitors (e.g., methoprene), are commonly used to control mosquitoes. However, it is unknown how these larvicides affect the mosquito internal microbiome and potentially alter their life history traits. The objectives of this study were three-fold: characterize the internal microbiota of Aedes larvae (Culicidae) in ephemeral forested mosquito habitat using high-throughput amplicon based sequencing; assess how mosquito control treatments affect the internal microbial communities of larval mosquitoes; and determine if changes to the microbiome resulted from direct or indirect treatment effects. The larval microbiome varied in community composition and diversity with development stage and treatment, suggesting potential effects of control compounds on insect microbial ecology. While microbial community differences due to Bti treatment were a result of indirect effects on larval development, methoprene had significant impacts on bacterial and algal taxa that could not be explained by indirect treatment effects. These results provide new information on the interactions between larval control treatments and insect microbial communities.