Palas Samanta

Histopathological and ultramicroscopical changes in gill, liver and kidney of Anabas testudineus (Bloch) after chronic intoxication of almix (metsulfuron methyl 10.1%+chlorimuron ethyl 10.1%) herbicide

Present study aimed to investigate the effects of almix herbicide on histopathological and ultrastructural changes in freshwater teleostean fish, Anabas testudineus (Bloch) under field and laboratory conditions with a dose of 8 g/acre and 66.7 mg/L respectively for 30 days. In field experiment fish species were reared in special type of cage submerged in pond. Cellular alterations of the concerned organs namely gills, liver and kidney were observed through light, scanning and transmission electron microscopy (SEM and TEM). Gill showed hypertrophy and oedema in secondary gill epithelium, and epithelial lifting under laboratory condition but in field condition hyperplasia was prominent. SEM study revealed necrosis, hyperplasia, excessive secretion of mucus and loss of microridges; while TEM study depicted degenerative changes in mitochondria and chloride cells and severe cytoplsmic vacuolation but the changes were comparatively less under field study. In liver, damage in acinar cells of hepatopancreas, degenerative changes in zymogen granules and detachment of hepatopancreatic acinar cells under laboratory condition were the serious changes, but in field condition fatty deposition is prominent. TEM study depicted dilated, degranulated and vesiculated rough endoplasmic reticulum, dilation and swelling of mitochondria and vacuolation in hepatocytes, but under field condition dilation of mitochondria and appearance of vacuolation were well marked. Kidney showed shrinkage of glomerulus, damaged and hypertrophied proximal convoluted tubule, loss of haematopoietic tissues under light microscopy; while ultrastructural changes like degenerative changes in mitochondria, deformed nucleus, dilation, fragmentation and vesiculation of rough endoplasmic reticulum, severe vacuolation in cytoplasm and necrosis were of very serious concern under laboratory condition, but in field condition epithelial cells showed less damage. Responses depicted that symptoms of lesions were more pronounced under laboratory than field condition and the degree of responses in different tissues were different under these two conditions. Therefore, evaluation of these histopathological lesions in concerned tissues may be established as symptomatic indicators for toxicity study in aquatic ecosystem.

Effects of multigenerational exposure to elevated temperature on reproduction, oxidative stress, and Cu toxicity in Daphnia magna

This study evaluated the effect of temperature (20 and 25°C) on reproduction, oxidative stress, and copper (Cu) toxicity in Daphnia magna across three generations (F0, F1, and F2). Exposing D. magna to elevated temperature significantly decreased the number of offspring per female per day, the time to first brood, and body length compared to exposure to the optimal temperature (p<0.05). In addition, elevated temperature induced a significantly higher production of reactive oxygen species and lipid peroxidation (p<0.05). These findings suggest that D. magna likely responded to thermal stress by investing more energy into defense mechanisms, rather than growth and reproduction. In addition, oxidative stress at the elevated temperature gradually increased with each generation, possibly owing to the reduced fitness of the offspring. Exposing D. magna to 25°C (EC50=34±3µgL(-1)) substantially increased the median effective concentration of Cu in all generations compared to exposure to 20°C (EC50=25±3µgL(-1)), indicating a decrease in acute toxicity at elevated temperature. However, elevated temperature significantly increased the oxidative stress induced by a sublethal concentration of Cu (10µgL(-1)). The interaction between elevated temperature and Cu exposure appears to be synergistic; however, this needs to be confirmed using multiple generations in a long-term experiment.

Comparative assessment of the adverse outcome of wastewater effluents by integrating oxidative stress and histopathological alterations in endemic fish

This study evaluated the adverse effect of wastewater effluents on three fish species, Carassius auratus, Zacco platypus, and Zacco koreanus, collected in the Eungcheon, Mihocheon, and Busocheon streams, respectively. Fish gills, liver, and kidneys from the mixing zone (MZ) and sites upstream (US) and downstream (DS) of the MZ were analyzed for oxidative stress responses and histology. Catalase and glutathione S-transferase activity was significantly higher at MZ and DS than from US (p<0.05), indicating induction of antioxidant defense mechanisms. Additionally, degree of tissue changes (DTC) indicated highest histopathological alteration in MZ, followed by DS and US. Integrated biomarker response (IBR) for oxidative stress and histopathological alterations showed higher values consistently for Z. koreanus than other two species. Water temperature, EC, and TN levels seemed to be responsible for the observed biomarker responses. These findings indicate that thermal hot spring effluent discharged into Busocheon steam induced the most significant impact on the cool water species (Z. koreanus). Overall, this study suggests that the IBR index is a very useful tool for monitoring in situ adverse effects of wastewater effluents on fish, particularly for histopathological alterations representing prolonged impact.

Integrated Biomarker Responses in Livers of the Pale Chub Zacco platypus for Risk Assessment of a Stream Contaminated by Wastewater Effluents

We evaluated the effects of wastewater effluents on pale chub (Zacco platypus) in a contaminated stream by integrating genotoxic, oxidative stress, histological, and physiological biomarkers. The metal pollution index indicated higher pollution loads at downstream sites (DS1 and DS2) compared with the upstream reference site. Significantly higher nuclear abnormality confirmed the existence of genotoxicity (p < 0.05) at downstream sites. Antioxidant activity (catalase and glutathione S-transferase) and lipid peroxidation levels in livers of Z. platypus were also significantly higher at the DS1 site (p < 0.05). The liver somatic index was also influenced, with abnormal histological alterations in the liver, possibly caused by heavy metal accumulation (Cd, Co, Cr, Mn, Ni, and Pb). The integrated biomarker response value was the highest at DS1 (13.74) followed by DS2 (1.94), indicating that wastewater effluents had the potential to cause adverse effects on Z. platypus inhabiting receiving stream.