## 3 Results
### Animal Condition and Tissue Neuroxidative Responses
Somewhat in line with SOD inhibition, lipid peroxidation (based on malonaldehyde (MDA) levels) showed, in general, higher values in liver (from 0.091 to 0.144 nmol\(\cdot\)mg\({}^{-1}\) protein), followed by brain (from 0.035 to 0.084 nmol\(\cdot\)mg\({}^{-1}\) protein) and muscle (from 0.025 to 0.031 nmol\(\cdot\)mg\({}^{-1}\) protein; Figure 4). Hg exposure did not affect LPO in fish muscle, except in fish co-exposed to warming and acidification, which revealed significantly lower values (i.e., 0.026 \(\pm\) 0.006 nmol\(\cdot\)mg\({}^{-1}\) protein in CONT + A + W treatment) compared to their non-contaminated counterparts (i.e., 0.040 \(\pm\) 0.012 nmol\(\cdot\)mg\({}^{-1}\) protein in A + W treatment; \(p\) = 0.02 Student's \(t\)-test; Figure 4a). Similarly, in the liver, no significant differences were observed between non-contaminated and Hg-contaminated fish (\(p\) > 0.05), but rather  
Figure 3: Superoxide dismutase (SOD) activity (percentage inhibition, mean \(\pm\) SD) in _S. senegalensis_ muscle (**a**), liver (**b**), and brain (**c**) after 28 days of Hg exposure. White bars represent non-contaminated treatments (non-CONT) and gray bars represent Hg-contaminated treatments (CONT). CTR—seawater temperature set at 19 °C and pH set at 8.0 units; A—seawater temperature set at 19 °C and pH set at 7.6 units; W—seawater temperature set at 23 °C and pH set at 8.0 units; A + W—seawater temperature set at 23 °C and pH set at 7.6 units. Different small letters denote significant differences between non-CONT treatments (ANOVA, \(p\) < 0.05). Different capital letters denote significant differences between CONT treatments (ANOVA, \(p\) < 0.05). Asterisks (*) represent differences between non-CONT and CONT for the same conditions (Student’s \(t\)-test: * \(p\) < 0.05; ** \(p\) < 0.005; *** \(p\) < 0.0005). between those exposed to control or altered abiotic conditions (i.e., significantly higher LPO in CONT + A + W treatment compared to CONT + W treatment; \(p\) = 0.0035; Figure 4b). As for the brain, while Hg contamination significantly increased LPO under control temperature and pH levels (i.e., control treatment presented significantly lower LPO than CONT treatment; \(p\) = 0.047 Student's _t_-test), the opposite trend was observed in fish exposed to warming (i.e., CONT + W presented an MDA concentration significantly higher than non-CONT + W treatment: \(p\) = 0.017 Student's _t_-test; Figure 4c). Brain AchE activity in non-CONT and CONT fish is shown in Figure 5.  
Figure 4: Lipid peroxidation in malondialdehyde (MDA) concentration (nmol-mg\({}^{-1}\) protein, mean \(\pm\) SD) in _S. senegalensis_ muscle (**a**), liver (**b**), and brain (**c**) after 28 days of Hg exposure. White bars represent non-contaminated treatments (non-CONT) and gray bars represent Hg-contaminated treatments (CONT). CTR—seawater temperature set at 19 \({}^{\circ}\)C and pH set at 8.0 units; A—seawater temperature set at 19 \({}^{\circ}\)C and pH set at 7.6 units; W—seawater temperature set at 23 \({}^{\circ}\)C and pH set at 8.0 units; A + W—seawater temperature set at 23 \({}^{\circ}\)C and pH set at 7.6 units. Different small letters denote significant differences between non-CONT treatments (ANOVA, \(p\) < 0.05). Different capital letters denote significant differences between CONT treatments (ANOVA, \(p\) < 0.05). Asterisks (*) represent differences between non-CONT and CONT for the same conditions (Student’s _t_-test: *_p_ < 0.05). In non-contaminated treatments (i.e., non-CONT), AchE activity ranged between 2.60 and 2.84 nmol-min\({}^{-1}\cdot\)mg\({}^{-1}\) protein, not evidencing significant differences among climate change scenarios (\(p>0.05\); Figure 5).