A single entomopathogenic nematode infection assay for Drosophila melanogaster larvae ☆

The entomopathogenic nematodes (EPNs) Steinernema carpocapsae and Steinernema hermaphroditum can efficiently infect the fruit fly, Drosophila melanogaster. The EPN infective juvenile (IJ) stage is the free-living and non-feeding stage that seeks out suitable insects to infect. While previous studies have described successful infection of D. melanogaster larvae with a standard amount of 100 IJs, the pathogenicity of a single IJ nematode towards insects remains poorly understood. Given the variability in pathogenesis among individual IJs, investigating the ability of a single IJ to cause infection in fly larvae addresses a significant gap in our understanding of host-parasite interactions. This protocol aims to evaluate the infection efficiency of a single IJ of S. carpocapsae and S. hermaphroditum. This information contributes towards a better understanding of the EPN-insect interactions and promises to improve the use of EPNs in pest management strategies. The method is summarized below: center dot Individual third instar wild-type D. melanogaster larvae are infected with either a single IJ or 100 IJs of either nematode species. Uninfected control larvae are treated with sterile water. center dot Larval survival is monitored over time. center dot Survival curves are generated, and results are statistically analyzed to determine the effect of a single nematode on the fly larval mortality.