The use of selected biomarkers, fatty acid and histopathology features to detect the possible toxic effects of the penconazole-containing fungicide Topas on marine clam siphons (Ruditapes decussatus)

Widespread use of pesticides in agriculture has the potential to harm non-target creatures diffusely and contaminate aquatic habitats through leaching and runoff events. Triazoles are among the fungicides used extensively worldwide due to their efficacy against fungal crop diseases and their broad spectrum of action. In this study, the impact of Topas on the antioxidant defence system, fatty acid composition and histopathological injuries was experimentally examined under three concentrations (4, 40, and 400 µg L-1) over 96 hours in Ruditapes decussatus siphons. Our results showed that Topas exposure induced a significant decrease in the levels of saturated fatty acids. However, an increase of monounsaturated fatty acids and polyunsaturated fatty acids, mainly the eicosapentaenoic (C20:5n-3), docosahexaenoic (C22:6n-3) and arachidonic (C20:4n-6) acids. Topas exposure enhanced the levels of hydrogen peroxide, malondialdehyde and protein carbonyls and altered enzymatic and non-enzymatic antioxidant status in all treated clams. Acetylcholinesterase activity was inhibited with the increase of Topas concentrations. Eventually, histopathological changes detected in treated animals varied in a concentration-dependent manner and were herein consistent with the biochemical outcomes. Our findings shed new light on the relationship between redox state and fatty acid composition changes, allowing us to understand Topas-triggered toxicity.