Fig 1.
Effect of exposure to single and combined agricultural agents on honeybee survival.
Survival is expressed as the percentage of cumulated number of surviving bees during the monitoring period of 11 days for each treatment group with n = 180 (MMH = E. faecalis strain MMH594, FLY = E. faecalis strain FLY1). Asterisks indicate differences in the survival rate after 11 days of individuals exposed to different stressors, * ≤ 0.005, ** ≤ 0.001, *** ≤ 0.0001 (Kaplan-Meier survival analysis, log Rank test for overall comparison).
Table 1.
Pairwise differences of honeybee worker survival rate 11 days post oral exposure to thiacloprid and E. faecalis and control diet.
Fig 2.
Quantity of food uptake by honeybees depending on the diet.
Food consumed representing the average mean amount of diet consumed in ml per bee per day during the 11-day monitoring period. Diets were inoculated with potential agricultural stressors (C = control, MMH = E. faecalis strain MMH594, FLY = E. faecalis strain FLY1, THIA = thiacloprid) with n = 1341 bees in total after 11 days (THIA n = 167, MMH n = 164, FLY n = 169, CONTROL n = 157, MMH+THIA n = 161, FLY+THIA n = 173, MMH+FLY n = 175, MMH+FLY+THIA n = 175; food consumption was controlled for bees per diet). Results represent mean values ± 2 s.e.m. Asterisks indicate differences in average food consumed per bee, * ≤ 0.005, ** ≤ 0.001, *** ≤ 0.0001; post hoc comparisons adjusted with Bonferroni (alpha = 0.005). Bars are indicated in: black = control, dark-grey = MMH, light-grey = FLY, red = THIA, shaded black = MMH+FLY, shaded dark-grey = MMH+THIA, shaded light-grey = FLY+THIA, shaded red = MMH+FLY+THIA.
Table 2.
Pairwise differences in feed quantity ingested by honeybee workers between diets inoculated with thiacloprid and E. faecalis.
Fig 3.
Lysozyme-like activity in the haemolymph of honeybees after being exposed to thiacloprid and E. faecalis.
General antibacterial activity measured as the diameter of the lytic zone on agar plates, transformed to lysozyme equivalents (μg/ml). Different enzyme activity in the haemolymph as a result of all possible different diet combinations as well as single stress exposure (C = control, MMH = E. faecalis strain MMH594, FLY = E. faecalis strain FLY1, THIA = thiacloprid). Asterisks indicate differences in the lysozyme-like activity, * ≤ 0.005, ** ≤ 0.001, *** ≤ 0.0001. Results represent mean values ± 2 s.e.m, Kurskal-Wallis test, n = 16 for each treatment group. Bars are indicated in: black = control, dark-grey = MMH, light-grey = FLY, red = THIA, shaded black = MMH+FLY, shaded dark-grey = MMH+THIA, shaded light-grey = FLY+THIA, shaded red = MMH+FLY+THIA.
Fig 4.
ROS concentration in the gut of honeybees after being exposed to different agricultural agents.
Differences in the mean concentration of reactive oxygen species in honeybee midguts, adjusted to the units of protein, when feeding on different diets. Diets were inoculated with potential agricultural stressors (C = control, MMH = E. faecalis strain MMH594, FLY = E. faecalis strain FLY1, THIA = thiacloprid). Results represent mean values ± 2 s.e.m, ANOVA, n = 16 for each treatment group. Bars are indicated in: black = control, dark-grey = MMH, light-grey = FLY, red = THIA, shaded black = MMH+FLY, shaded dark-grey = MMH+THIA, shaded light-grey = FLY+THIA, shaded red = MMH+FLY+THIA.
Table 3.
Pairwise differences in lytic like activity of honeybee workers after feeding on different stressors.