2012 Annual Report
Two laboratory experiments were conducted to further understand the role of gut microbes on the feeding behavior of omnivorous insects. The first experiment aimed to resolve the importance of Enterococcus faecalis on seed consumption by Harpalus pensylvanicus. Four treatments were established (each with approximately 30 individuals). The first two treatments were fed antibiotics, and one of the treatments received E. faecalis. The second two treatments received no antibiotics, and one of these treatments received E. faecalis. Seeds were fed to H. pensylvanicus, then the antibiotics were administered (or a control diet) for 10 d to remove the microbial community from the beetle guts. Seeds were again fed to the beetles. Finally, the E. faecalis (or a control diet) were fed to the beetles, followed by a final quantity of seeds. After each seed-feeding, seed consumption rates and various feeding metrics (efficiency of converted digested material, efficiency of converted ingested material, and approximate digestibility) were measured for each treatment. Enterococcus faecalis increased seed consumption rates by 40%, but only if the beetle had received antibiotics. This work clearly shows that E. faecalis contributes to granivory rates in omnivorous beetles, and suggests that resident bacterial communities affect the ability of E. faecalis to function.
The second experiment investigated how antibiotics affect the dietary preferences of the cricket, Gryllus pennsylvanicus. Prey (moth eggs) and seeds (lambsquarters) were offered under choice conditions to crickets that had received antibiotics or not (n = 30, each). The quantity of each food was subsequently measured, as were various feeding efficiency metrics. The experiment has been completed, but the data awaits analysis.