Acute effects of neonicotinoid insecticides on Mytilus galloprovincialis: A case study with the active compound thiacloprid and the commercial formulation calypso 480 SC

Pesticides can enter aquatic environments potentially affecting non-target organisms. Unfortunately, the effects of such substances are still poorly understood. This study investigated the effects of the active neonicotinoid substance thiacloprid (TH) and the commercial product Calypso 480 SC (CA) (active compound 40.4% TH) on Mytilus galloprovincialis after short-term exposure to sublethal concentrations. Mussels were tested for seven days to 0, 1, 5 and 10 mg L-1 TH and 0, 10, 50 and 100 mg L-1 CA. For this purpose, several parameters, such as cell viability of haemocytes and digestive cells, biochemical haemolymph features, superoxide dismutase (SOD) and catalase (CAT) enzymatic activity of gills and digestive gland, as well as histology of such tissues were analysed. The sublethal concentrations of both substances lead to abatement or completely stopping the byssal fibres creation. Biochemical analysis of haemolymph showed significant changes (P < 0.01) in electrolytes ions (Cl-, K+, Na+, Ca2+, S-phosphor), lactate dehydrogenase (LDH) enzyme activity and glucose concentration following exposure to both substances. The TH-exposed mussels showed significant imbalance (P < 0.05) in CAT activity in digestive gland and gills. CA caused significant decrease (P < 0.05) in SOD activity in gills and in CAT activity in both tissues. Results of histological analyses showed severe damage in both digestive gland and gills in a time and concentration-dependent manner. This study provides useful information about the acute toxicity of a neonicotinoid compound and a commercial insecticide on mussels. Nevertheless, considering that neonicotinoids are still widely used and that mussels are very important species for marine environment and human consumption, further researches are needed to better comprehend the potential risk posed by such compounds to aquatic non-target species.