Avoidance behavior by wingless drosophila melanogaster (Diptera: drosophilidae) of food sources infected with lipopolysaccharides

Individuals conserve energy through pathogen avoidance by preventing costly immune responses. Lipopolysaccharides (LPS) are gram-negative bacterial endotoxins that initiate an immune response without causing infection. We tested adult male and female wingless Drosophila melanogaster using lipopolysaccharide concentrations of 0.5 mg/ml and 1.0 mg/ml. Control flies were not pre-exposed to lipopolysaccharides, while experimental flies were exposed to a food source containing lipopolysaccharides. We placed an individual fly into an arena that contained an uninfected food source (no LPS) and an infected food source (LPS). For each control (n = 30) and experimental (n = 30) fly, we recorded how many times the fly landed on each food source, and the duration of time spent on each food source. There were no significant differences in number of visits or time spent on the infected food source by control males or control females at 0.5 mg/ml LPS. There were no significant differences in number of visits or time spent on the infected food source by experimental males or experimental females at 0.5 mg/ml LPS. There were no significant differences in number of visits or time spent on the infected food source by control males or control females at 1.0 mg/ml LPS. Experimental males pre-exposed to 1.0 mg/ml LPS spent significantly less time on the infected food source and had significantly less visits to any food source. Experimental females had no significant differences in number of visits or time spent on the infected food source at 1.0 mg/ml LPS. There was a significantly smaller proportion of active flies following exposure to the 1.0 mg/ml concentration of lipopolysaccharides in both males and females. These differential results between male and female flies demonstrate sex-specific behaviors following exposure to an endotoxin.