Toxicity effects of microplastics individually and in combination with Aeromonas hydrophila on freshwater crayfish (Astacus leptodactylous)

Abstract

Opportunistic pathogens, such as Aeromonas hydrophila, can cause damage to freshwater crayfish (Astacus leptodactylous) in some situations. In addition to direct damage to the body, microplastics (MPs) can also be responsible for transmitting pathogens to the animal. Accordingly, this research was prepared to investigate the effects of MP on the damage caused by A. hydrophila exposure in A. leptodactylous. Hepatic oxidative biomarkers, blood biochemical indices, and clinical signs were investigated in freshwater crayfish co-exposed to MPs (500 and 1000 mg kg⁻¹) and A. hydrophila (5 and 10% of the median lethal dose (LD50)) for 30 days. In the hemolymph of infested crayfish with A. hydrophila, there were no significant changes in glutathione peroxidase activity or total antioxidant level. However, in some of the clinical parameters, exposure to MP alone had a significant effect. Cholesterol levels, glutathione peroxidase, catalase, and the activity of γ-glutamyltransferase reduced, conversely, glucose, malondialdehyde, and aspartate aminotransferase increased. After co-exposure to A. hydrophila and MPs, certain parameters elevated in the hemolymph of crayfish such as glucose, activity of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase. However, total protein, cholesterol, γ-glutamyltransferase, glutathione peroxidase, catalase activity, and total antioxidants decreased. In contrast, elevation in malondialdehyde content and superoxide dismutase activity was observed in the hepatocytes of crayfish after co-exposure to A. hydrophila and MPs. To summarize, the investigation demonstrated that the interaction of MPs and A. hydrophila in crayfish has a synergistic effect on various factors.