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Aquatic Toxicology
Elsevier Science direct
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Although substantial knowledge of mercury toxicity in fish has been assembled; until now, studies investigating
the toxic impacts in Nile tilapia (Oreochromis niloticus) following dietary exposure to organic methyl mercury
(MeHg) are less prolific. Accordingly, the current study aimed to evaluate the impacts of MeHg on neurobehavioral
and immune integrity in Nile tilapia after dietary exposure. Two hundred and twenty-five juvenile
Nile tilapia (19.99 ± 0.33 g) were allocated into five groups in triplicates (15 fish/replicate). G1, G2, G3, G4, and
G5. O. niloticus were fed corresponding basal diets containing 0, 0.5, 1, 1.5, and 2 mg/kg diet MeHg chloride
(MeHgCl) daily for 30 days, zero value represented the control G1 group. The results showed that MeHg induced
significant alterations in O. niloticus behavior, the swimming behavior was significantly decreased, while
scratching, biting, and fin tugging behaviors were significantly augmented. Moreover; chasing, mouth pushing,
and butting behaviors were significantly increased in all the exposed groups. MeHg significantly decreased brain
acetylcholine esterase (AChE) and serum immunoglobulin M (IgM) levels in all the exposed groups. Meanwhile,
serum levels of lysozyme (LYZ), nitric oxide (NO), superoxide dismutase (SOD) malondialdehyde (MDA), protein
carbonyl (PCO), and 8 hydroxy 2 deoxyguanosine (8OH2dG) were significantly elevated in all the exposed
groups except for serum reduced glutathione (GSH) content was significantly decreased implying oxidative stress
(OS), lipid peroxidation (LPO), protein, DNA damage and impaired immune response of the exposed tilapia.
MeHg significantly altered transcriptional expression of immune-related genes including (TNF-α, IL-1β, and IL-8,
and IL-10) in all the exposed groups. From the obtained outcomes, the present research is the premier to
investigate that dietary MeHg exposure in O. niloticus significantly induced neurobehavioral and immune defense
impairments in a dose-related manner. This study exhibits that dietary MeHg may pose a potential threat to the
O. niloticus populations.
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