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Heavy metals and herbicide are gaining serious environmental concern in aquatic toxicology due to its adverse effects on aquatic organisms especially amphibians. Accordingly, present study first time evaluated the acute toxicity of two heavy metals [arsenic (As3+) and chromium (Cr6+)] and a herbicide (Almix) to Indian skittering frog tadpole, Euphlyctis cyanophlyctis. The LC50 values of As, Cr and Almix for 24, 48, 72 and 96 h were 73.58, 56.31, 43.58 and 32.58 mg L−1; 326.68, 224.31, 171.92 and 141.99 mg L−1; and 1297.85, 1148.22, 1033.62 and 955.17 mg L−1, respectively. It also revealed the concentration- and time-dependent increased mortality rate under these toxicants. The safety concentrations (SC) of As, Cr and Almix to tadpoles were 3.26, 14.20 and 95.52 mg L−1, respectively. The findings disclosed that As is highly toxic to E. cyanophlyctis than Cr and Almix. Alkaline phosphatase (ALP) activity showed varied responses to exposed chemicals. In particularly, ALP activity reduced significantly for Cr treatment. Glutathione S-transferase (GST) activity in E. cyanophlyctis was significantly inhibited by As treatment (p 0.05). The As toxicity correlates positively with GST inhibition (r = 0.779, p 0.05). This result indicated that GST play a crucial role for regulating the tadpole mortality and intoxication by As, Cr and Almix. Overall, our findings demonstrate the different levels of toxic sensitivity (adverse effects) under different toxicants on E. cyanophlyctis tadpoles. Finally, the present findings could be used as baseline information of toxicosis for metalloid, heavy metal and herbicide exposures in wild frog populations.

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 glyphosate based herbicide, Excel Mera 71 at a dose of 17.20mg/l on enzyme activities of acetylcholinesterase (AChE), lipid peroxidation (LPO), catalase (CAT), glutathione-S-transferase (GST) and protein content were measured in different tissues of two Indian air-breathing teleosts, Anabas testudineus (Bloch) and Heteropneustes fossilis (Bloch) during an exposure period of 30 days under laboratory condition. AChE activity was significantly increased in all the investigated tissues of both fish species and maximum elevation was observed in brain of H. fossilis, while spinal cord of A. testudineus showed minimum increment. Fishes showed significant increase LPO levels in all the tissues; highest was observed in gill of A. testudineus but lowest LPO level was observed in muscle of H. fossilis. CAT was also enhanced in both the fishes, while GST activity in liver diminished substantially and minimum was observed in liver of A. testudineus. Total protein content showed decreased value in all the tissues, maximum reduction was observed in liver and minimum in brain of A. testudineus and H. fossilis respectively. The results indicated that Excel Mera 71 caused serious alterations in the enzyme activities resulting into severe deterioration of fish health; so, AChE, LPO, CAT and GST can be used as suitable indicators of herbicidal toxicity.

Common carp, Cyprinus carpio, was exposed to 1% and 5% dietary heavy oil for 2 weeks. Higher polyaromatic hydrocarbons (PAHs) accumulation induced higher hepatic EROD activity in exposure groups compared with the control group. Significant histological alternations were observed in the liver such as nuclear and cellular hypertrophy, accumulation of eosinophilic granules in cytoplasm, nuclear degeneration and fibrillar inclusion in cytoplasm. Severe damage of the kidney was indicated by nuclear and cellular degeneration, and ultimately necrosis in the tubular epithelium cells. In addition, dilated glomerulus with hemorrhage was found in the renal capsule. The mean assessment value (MAV) and degree of tissue changes (DTC), as semi-quantitative analyses, were significantly increased with concentration and duration of exposure. Likewise, frequencies of pathological lesions in both liver and kidney were also increased with concentration and duration of exposure.