STUDIES ON HISTOMORPHOLOGICAL CHANGES IN THE FISH, Oreochromis mossambicus EXPOSED TO TITANIUM DIOXIDE NANOPARTICLES – AN IRRECOVERABLE DAMAGE

Titanium dioxide nanoparticles (TiO2NPs) manufactured worldwide in large quantities was used widely in consumer products, photocatalytic cleaning and as antibacterial agent. The present study emphasis on TiO2NPs induced irrecoverable histomorphological damage in gill, liver and brain tissues of the freshwater fish, Oreochromis mossambicus. TiO2NPs at 16.4 mg/ L concentration (1/10th of LC50-96 h, hours) was applied for short term (96 h) and long term (60 d, days) durations along with control group. Gill tissue exposed to nanoparticles for 96 h showed epithelial lifting, vacuolization, hyperplasia, aneurysm and absence of secondary lamella, and these notable lesions were more prominent after 60 d of treatment. In 96 h exposed specimens, the liver tissue showed severe vacuolization and melanomacrophage aggregation, whereas spindle shaped nuclei and severe necrosis was observed after 60 d of treatment. Histopathology of brain tissues after short-term exposure resulted in neuronal degeneration in cerebral region while vacuolar changes with empty sacs were noted after long-term exposure. Withdrawal of nanoparticles for 60 d after long-term treatment, showed similar pathological lesions in gill, liver and brain tissues thereby confirming the irrecoverable tissue damages due to nanoparticles exposure. The study provides basic knowledge on nanoparticles induced sublethal and irreparable histopathological lesions in the fish, which may be considered as the direct effect of toxicant that ultimately make the fish less fit for better survival.