Abstract
The environment experienced by individuals during their juvenile stages has an impact on their adult stages. In holometabolous insects like Drosophila melanogaster, most of the resource acquisition for adult stages happens during the larval stages. Larval-crowding is a stressful environment, which exposes the larvae to scarcity of food and accumulation of toxic waste. Since adult traits are contingent upon larval stages, in larval-crowding like conditions, adult traits are prone to get affected. While the effect of resource limited, poor-developmental environment on adult immune response has been widely studied, the effect of adaptation to resource-limited developmental environment has not been studied, therefore in this study we assayed the evolution of ability to survive infection in adult stages as a correlated response to adaptation to larval crowding environments. Using four populations of Drosophila melanogaster adapted to larval crowding for 240 generations and their respective control populations, we show that populations adapted to larval crowding show an improved and evolved post-infection survivorship against a gram-negative bacteria Pseudomonas entomophila. Whereas, against a gram-positive bacteria Enterococcus faecalis, no difference in post-infection survivorship was observed across control and selected populations. In this study, we report the co-related evolution of pathogen-specific increased survivorship post-infection in populations of Drosophila melanogaster as a result of adaptation to larval crowding environment.
Highlights
According to the "Developmental origin of health and disease" theory, nutrition and environment available to an individual during critical developmental stages can have a potentially permanent effect on its ability to defend itself from disease [1]
Evolution of survivorship post-infection in populations of Drosophila melanogaster adapted to larval crowding programmed by events in early life [2,3,4]
We observed an effect of selection history and larval density on adult survivorship postinfection when the flies were infected with gram-negative bacteria, but not when infected gram-positive bacteria
Summary
According to the "Developmental origin of health and disease" theory, nutrition and environment available to an individual during critical developmental stages can have a potentially permanent effect on its ability to defend itself from disease [1]. Evolution of survivorship post-infection in populations of Drosophila melanogaster adapted to larval crowding programmed by events in early life [2,3,4] In both vertebrates [5,6,7] and invertebrates [8,9,10], there are many studies that suggest that poor nutritional conditions during development lead to poor adult immune responses. We used populations of Drosophila melanogaster that have evolved for 240 generations in poor developmental (larval-crowding) conditions (MCU populations) and their low-density ancestral controls (MB populations) Larvae from both the regimes were grown at high and low larval densities, and we subsequently measured their survivorship post infection in adult stage with either a gram-negative bacterium Pseudomonas entomophila or a gram-positive bacterium Enterococcus faecalis. Along with causing severe damage to the gut, both the bacteria are known to cause systemic pathogenic infection [29, 30]
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