Relationship between Mn2+ treatments and biogenic amine levels. Linear mixed regression estimates (95% CIs) and data for (a) octopamine, (b) dopamine and (c) serotonin in honeybee brains as a function of Mn2+ levels (see table 1 for statistics). Levels of (d) octopamine (t34 = −4.5631, p = 0.00006, n = 18), (e) dopamine (t34 = −2.5393, p = 0.0159, n = 18) and (f) serotonin (t31 = −0.3063, p = 0.7614, n = 18) from fly brains. Data are presented as mean ±s.e. Different letters above bars denote statistical difference.
Effects of Mn2+ on honeybee foraging. (a) Honeybee forager tagged with an RFID transponder. (b) Boxplots show age at onset of foraging for bees treated with 0–50 mM Mn2+ (χ2 = 25.4634, d.f. = 4, p < 0.0001). Different lower case letters below bars denote statistically different groups. (c) Kaplan–Meier survival curves showing the number of foraging trips completed by honeybees treated with 0–50 mM Mn2+ between onset of foraging and death (χ2 = 17.6, d.f. = 1, p < 0.0001). (d) Polynomial regression of the relationship between time spent outside the hive per foraging trip and number of foraging trips taken (F6,393 = 85.55, p < 0.001, R2 = 0.51).