Evaluation of health status of Oreochromis niloticus (L.) based on brain optic tectum morphopathology

Abstract

Oreochromis niloticus (L.) health status was evaluated based on brain optic tectum morphopathology. O. niloticus was exposed to sub-lethal Almix (66.67 mg/L) and Excel Mera 71 (17.2 mg/L) concentrations for 30 d. Results revealed that herbicides exposure caused different morphological changes in brain optic tectum. Almix treatment showed comparatively higher morphological changes compared with Excel Mera 71. The mean assessment value (MAV) showed significantly higher (p < 0.0001) value in Almix (4.36±0.09) and Excel Mera 71 (3.60±0.09) exposure, in comparison with control fish (0.09±0.02). Stratum album centrale (SAC) and stratum periventriculare (SPV) were most affected layer compared with others. The observed morphological alterations revealed impaired visual, sensory and motor functions, which ultimately alters brain physiology. In particularly, the existence of necrosis in neural cells, loss of Nissl substances, gliosis and vacuole formations under Almix and Excel Mera 71 exposure indicated neurotoxic nature of these herbicides. However, higher prevalence under Almix treatment indicated higher neurotoxic potential than Excel Mera 71. Therefore, the results presented here are highly significant to toxicologist considering its neurotoxic property. Finally, further studies are needed to explore detailed mode of action of neurotoxicity for adverse outcome pathways (AOP) development at molecular level.