Toxicological impacts of environmentally equivalent microplastics and cadmium co-exposure in tropical freshwater crab Sartoriana spinigera

The toxic effects of microplastics (MPs) and trace metals on freshwater crustaceans remain poorly understood; therefore, current research examined the individual and combined effects of MPs, specifically polystyrene (PS) and polyethylene terephthalate (PET), and cadmium (Cd) on female freshwater crabs, Sartoriana spinigera, emphasizing behaviour, growth, haematobiochemical parameters, and tissue morphology. Crabs were exposed to five treatments (PS, PET, Cd, PS + Cd, PET + Cd) and a control for 14 days. The exposure caused notable behavioural and growth alterations, with the lowest survival rate (33.33% ± 6.67%) observed in the PS group. Bioaccumulation was highest in the gills for PS (44.67 ± 4.49 items/g) and in the hepatopancreas for PET (36.33 ± 2.41 items/g). Liver health markers showed increased alanine aminotransferase in the Cd group (9.33 ± 0.37 U/L), and elevated aspartate aminotransferase levels were noted in the PS group (25.83 ± 0.44 U/L). Additional stress markers, including total cholesterol, triglycerides, brix, glucose, and total protein, confirmed physiological disturbance in toxicant-exposed groups. Histomorphological analysis revealed structural changes in the hepatopancreas and gills, indicating impaired organ function. Overall, co-exposure caused greater physiological stress than individual treatment alone, demonstrating a combined toxic effect. These findings enhance our understanding of the complex interactions between MPs and toxic metals in tropical freshwater ecosystems, providing valuable insights for future research into multi-stressor impacts on crustacean physiology and toxicology.