Nimai Chandra Saha

The increasing use of nano-based products raises concerns regarding potential risks related to their manufacturing, transportation, waste disposal, and management operations. We used the riverine carp, Capoeta capoeta, as an aquatic animal model to demonstrate the acute toxicity of silver nanoparticles (Ag-NPs). This study focuses on acute toxicity first, and then integrates the findings through histopathology, hematological, and biochemical testing of lethal and sub-lethal Ag-NPs exposures. Red blood corpuscles (RBC), white blood corpuscles (WBC), hematocrit, and total serum glucose levels were significantly lower in Ag-NPs-exposed fish than in control fish. Total serum protein, triglycerides, cholesterol, and albumin were all significantly greater in exposed fish. This research focused on the impacts of Ag-NPs on gills and liver tissue, and it was found that the level of injury escalated as the concentration of Ag NPs increased. Epithelial lifting of secondary lamellas (ELSL), epithelial hypertrophy (EH) of secondary lamellae (SL), leukocyte infiltration (LI), and bottom hyperplasia (BH) were all detected in Ag-NPs-exposed fish. In Ag-NPs-treated liver cross-sections of Capoeta capoeta, macrophage aggregates (MA), fatty liver (FL), sinusoid dilatation (SD), and necrosis (N) were identified. Ag-NPs dosages, according to biomarker representations, elicit stress-specific biochemical and physiological effects, compromising the general overall health status of aquatic animals. The gradients of toxic responses across exposure concentrations and portrayals of disrupted fish health with increasing silver nanoparticle exposure time indicate a reduced physiological ability for surviving in the wild.

Disrupted behavior and respiratory distress effects of 96-h acute deltamethrin exposures in adult Mozambique tilapia, Oreochromis mossambicus, were investigated using behavioral indices and opercular movement, respectively. Deltamethrin concentrations were found to be associated with toxicological (lethal and sublethal) responses. At 24, 48, 72, and 96 h, the LC50 values and 95% confidence limits were 12.290 (11.174–14.411 µg/L), 12.671 (11.334–15.649 µg/L), 10.172 (9.310–11.193 µg/L), and 8.639 (7.860–9.417 µg/L), respectively. The GUTS-model analysis showed that GUTS-SD (stochastic death) with a narrow tolerance distribution in deltamethrin exposed O. mossambicus populations was more sensitive than the GUTS-IT (individual tolerance) model. Prior to death, exposed fish demonstrated concentration-dependent mortality and disturbed behavioral responses, including uncoordinated swim motions, increased mucus secretion, unbalanced and unpredictable swimming patterns, and inactivity. The altered behavioral patterns and increased opercular movement with increased deltamethrin levels and exposure time are strongly suggestive of neurotoxicity and respiratory distress, respectively. Adverse Outcome Pathways (AOPs), describing biological mechanisms and plausible pathways, highlighted oxidative stress and cholinergic effects as intermediate steps linked to respiratory distress and behavioral toxicity.

Diazinon exposures have been linked to the onset of toxic pathways and adverse outcomes in aquatic species, but the ecological implications on model species are not widely emphasized. The objective of this study was to determine how the organophosphate pesticide diazinon affected hematological (hemoglobin, total red blood count, total white blood count, and mean corpuscular hemoglobin), growth (condition factor, hepatosomatic index, specific growth rate), biochemical (total serum glucose, total serum protein), and endocrine (growth hormone, tri-iodothyronine, and thyroxine) parameters in Clarias batrachus after chronic exposure. Diazinon was administered at predefined exposure doses (0.64 and 1.28 mg/L) and monitored at 15, 30, and 45 days into the investigation. Observation for most biomarkers revealed patterns of decreasing values with increasing toxicant concentration and exposure duration. Correlation analysis highlighted a significant inverse relationship between variables (mean corpuscular hemoglobin, condition factor, specific growth rate, tri-iodothyronine, thyroxine, and total serum protein) and elevated chronic diazinon exposure concentrations. The integrated indices (IBR and BRI) indexes were used to provide visual and understandable depictions of toxicity effects and emphasized the relativity of biomarkers in terms of sensitivity and magnitude or severity of responses under graded toxicant exposures. The significant damage reflected by evaluated parameters in diazinon exposure groups compared to control portends risks to the health of local fish populations, including Clarias batrachus in aquatic systems adjacent to agrarian landscapes.