## Materials and Methods
### Oxidative Stress of Loggerhead Sea Turtles Erythrocytes  
SOD and GST, \(2\times 10^{6}\) RBCs/mL of loggerhead turtles exposed and not exposed to MeHg (0, 1 and 5 mg L\({}^{-1}\)) were used to assess oxidative stress markers. These were lysed with four volumes of ice-cold HPLC, and then centrifugated at 10,000 \(g\) for 15 min at 4 \({}^{\circ}\)C. The supernatant (RBCs lysate) was collected for assaying and stored at \(-80\)\({}^{\circ}\)C. For the MDA assay, \(2\times 10^{7}\) RBCs/mL of loggerhead turtles exposed and not exposed to MeHg (0, 1, and 5 mg L\({}^{-1}\)) were used. The samples were centrifugated at 2500 rpm for 5 min at 4 \({}^{\circ}\)C, and then resuspended in 1 mL of MEM. RBCs were collected and stored at \(-80\)\({}^{\circ}\)C until use. The activity of Superoxide Dismutase (SOD) and Glutathione S-Transferases (GST), and the levels of Malonaldehyde (MDA) were determined in RBCs lysate using commercial kits (Superoxide Dismutase Assay Kit [Item No. 706002], Glutathione S-Transferase Assay Kit [Item No. 703302],and TBARS assay kit [Item No. 10009055], Cayman Chemical Co, Ann Arbor, MI, USA), following the manufacturer's protocol for each Kit. The Superoxide Dismutase (SOD) activity measuring kit is based on a method in which xanthine and xanthine oxidase react with tetezolium salt (2-(-4-iodophenyl)-3-(4-nitropenol)-5-phenyl tetrazolium chloride), generating superoxide radicals, which then react and form formazan red. The SOD activity was then measured by the degree of inhibition of this reaction. In a 96-well microplate, 10 \(\upmu\)L of the Standard SOD enzyme (included in the kit, in AG wells) were served. In the rest of the microplate, 10 \(\upmu\)L of previously exposed and unexposed lysed RBCs (0, 1, and 5 mg L\({}^{-1}\) of MeHg) were served (in triplicate), then, 20 \(\upmu\)L of the diluted radical detector were added to all wells. To start the reaction, 20 \(\upmu\)L of diluted xanthine oxidase were added to all wells, both standard and samples. Xanthine oxidase enzyme was not added for the control and the recorded readings were used to make the absorbance correction once the measurements were made. The plate was shaken for 30 min at room temperature and then the absorbance at 440-460 nm was measured in a plate reader (Elisa reader Expert 96 ASYS Hitech, Eugendorf, Austria). The average absorbance of each standard and sample was calculated and then corrected, subtracting the absorbance recorded in the control. The linearized rate (LR) of all standards was calculated, first dividing the absorbance of standard A by itself and then that of the other BG standards dividing the value recorded in A, by those that were recorded in each of the BG standards. This means LR for Std A = Abs Std A/Abs Std A; LR for Std B = Abs Std A/Abs Std B, and so on. The linear standard SOD rate (LR) was plotted against the final SOD activity (U/mL). The SOD activity of the samples was calculated while using the equation that was obtained from the linear regression of the standard curve, substituting the linearized rate (LR) for each sample. A unit of SOD is defined as the amount of enzyme that is required to exhibit a 50% dismutation of the superoxide radical. SOD activity is standardized while using the coupled cytochrome c and xanthine oxidase assay. The results were presented in international units per millititer (U/mL). \[OD\left(\frac{U}{mL}\right)=\left[\left(\textit{sample}\;LR-y-\frac{intercept }{slope}\right)\times\left(\frac{0.23\;mL}{0.01\;mL}\right)\right]\times \textit{Sample dilution} \tag{1}\]  
The GST enzyme was quantified in triplicate in RBCs lysate. 150 \(\upmu\)L of assay buffer, 20 \(\upmu\)L of glutathione, and 20 \(\upmu\)L of each of the previously exposed and unexposed lysed RBC samples (0, 1, and 5 mg L\({}^{-1}\) MeHg) were served in a 96-well microplate. As a negative control, 170 \(\upmu\)L of test buffer and 20 \(\upmu\)L of glutathione were used, and as a positive control, 150 \(\upmu\)L of test buffer, 20 \(\upmu\)L of glutathione, and 20 \(\upmu\)L of reconstituted GST.