Abstract:
Anopheles merus can breed in a range of saltwater concentrations. The consequences of this
ability on the life history of adult An. merus are poorly understood. This study examined the effects
of exposure to 0, 2.1875, 4.375, 8.75, and 17.5 g/L of sodium chloride on An. merus. The effects on
larval development, adult longevity, fertility, and fecundity, as well as deltamethrin tolerance were
examined. The effect of larval salt exposure on the expression of defensin-1 in adults was examined by
quantitative Real-Time PCR. Finally, the effect of the larval salt concentration on microbial dynamics
was assessed by 16S Next Generation Sequencing. High concentrations of saltwater increased larval
development time and number of eggs laid, as well as deltamethrin tolerance. Larval exposure to
salt also reduced the expression of defensin-1. The exposure also had a significant effect on microbial
diversity in larvae and adults. The diversity of larvae decreased once adults emerged. Salt-tolerant
bacterial genera predominated in larvae but were absent in adults. High salt concentrations resulted
in greater abundance of Plasmodium-protective genera in adults. Although this study was conducted
on a laboratory strain of An. merus, these data suggest that osmoregulation has a significant effect on
the life history of the species with potential epidemiological consequences.
