Fig. 5. ROS-associated fluorescence levels in WT and skn-1 (ok2315) worms untreated and pretreated with GEE 1000 μg ml^–1 after MeHg exposure and 24-hour recovery. Aliquots of worm's lysates were incubated for 1 hour with 20 μM DCFDA (final concentration) at 20 °C and fluorescence was measured in duplicate in a microplate reader at 485 nm excitation and 520 nm emission wavelengths at room temperature. Data were normalized to protein content. Fluorescence levels were significantly increased in MeHg non-exposed groups in comparison to control and MeHg at 25 and 50 μM significantly decreased fluorescence levels in comparison to MeHg-non-exposed worms of the same group. No significant differences were detected between untreated and GEE-pretreated worms and between WT and skn-1 (ok2315) worms exposed to MeHg. (#) Represents a significant difference between control and the other groups non-exposed to MeHg by two-way ANOVA followed by Bonferroni's multiple comparison test (p < 0.05) and (*) represents a significant difference between MeHg-exposed and non-exposed worms of the same group by one-way ANOVA followed by the Bonferroni post hoc test (p < 0.05). Data are expressed as means of arbitrary fluorescence units (AFU) per μg of protein ± SEM, n = 4.