Histopathological Changes in Freshwater Crayfish Exposed to Silver Nanoparticles

Engineered nanoparticles (ENPs) have become increasingly common in various commercial, industrial, and medical applications; however, the very property that makes them desirable, their high reactivity, poses risks to environmental and human health. Previous studies have documented their toxicity to DNA and metabolic pathways. In this experiment, two different species of crayfish (Orconectes virilis and Procambarus clarkii) were exposed to silver nanoparticles (AgNPs). The experimental organisms were exposed to various concentrations of colloidal AgNPs: 0.0, 0.050, 0.107, 0.160, and 0.214 mg/L. Additional control treatments were established with parental compounds, silver nitrate (AgNO₃) and sodium borohydride (NaBH₄), used to synthesize the AgNPs. The experiment was conducted for 10 days. Collected tissues were embedded in paraffin and molds sectioned at 6 µm using a Spencer microtome. Slides were stained with hematoxylin-eosin dye and examined for pathological changes. Silver content was determined using a ThermoElemental Solaar M5 spectrophotometer in graphite furnace mode. Serotonin content was analyzed using ELISA immunoassay. Statistical variations in measurements were determined using the SPSS statistical package. Pathological changes were observed in crayfish gills, such as clubbing, loss of pillar cells, and hyperplasia. In exoskeleton, porous architecture and symptoms of demineralization were observed in 0.107, 0.160, and 0.214 mg/L AgNP and the related AgNO₃ concentrations. Ag from AgNP sources accumulated in proportion to the dose while Ag from AgNO₃ sources exhibited a nonconventional dose response. Serotonin levels significantly decreased in exposed brain tissue. Our results suggest that exposure to ENPs could have significant impact on the environment and on human health.