Figure 7.

Long-term memory assessment and its associated changes in MB synaptic organization at different times after avoidance learning in 1-day treatment experiments. (A) Foragers’ plant preferences for treated and (B) control subcolonies in a choice experiment between firethorn (fir) and privet (pri) leaves. On day 0, ants were offered treated (fir_CHX) or untreated (fir_Ctrl) firethorn leaves. Bars show the proportion of taken plant discs at different times after treatment. Different letters indicate significant differences among days (G-Test) and numbers at the bottom of each bar indicate the total number of ants that collected a disc during testing. (C) Density of synapsin-IR boutons in the ND lip and (D) total lip volume at different times after the incorporation of CHX-infiltrated leaves (fir_CHX, treatment). Following variations during a longer period of time after plant avoidance learning revealed that ND lip density transiently increased without calycal volumetric changes in the treated subcolony. (E) ND lip synapsin-IR boutons density and (F) lip volume at different times after incorporation of the untreated plant (fir_Ctrl, control). Incorporation of control leaves did not promote significant changes in the lip. Dots represent the mean value and solid lines the S.D. Horizontal dotted lines indicate mean bouton density quantified before treatment (day 0). Asterisks indicate significant differences between day 0 and different times after leaves incorporation into the fungus garden; *p < 0.05. Treatment: day 0, N = 5; day 2, N = 8; day 4, N = 8; day 15, N = 6. Control: day 0, N = 7; day 2, N = 7; day 4, N = 8; day 15, N = 8.