In the present work, the marine invertebrate Mytilus galloprovincialis was used as model organism to evaluate the toxic effects of the neonicotinoid Calypso 480 SC (CAL) following 20 days of exposure to sub-lethal concentrations of 7.77 mg L-1 (0.1% 96 h-LC50) and 77.70 mg L-1 (1% 96 h-LC50), and a recovery period of 10 days in uncontaminated seawater. Results revealed that exposure to both concentrations of CAL increased significantly mortality rate in the cells of haemolymph and digestive gland, while digestive gland cells were no longer able to regulate cell volume. Exposure significantly reduced haemolymph parameters (Cl-, Na+), affected the enzymatic activities of superoxide dismutase of digestive gland and catalase of gill, and caused also histopathological alterations in digestive gland and gills. Main histological damages detected in mussels were lipofuscin accumulation, focal points of necrosis, mucous overproduction and infiltrative inflammations. Interestingly, alterations persisted after the recovery period in CAL-free water, especially for haemocyte parameters (K+, Na+, Ca2+, lactate dehydrogenase, glucose). A slight recovery of histological conditions was detected. These findings suggested that sub-chronic exposure to the neonicotinoid insecticide caused significant alterations in both cell and tissue parameters of M. galloprovincialis. Considering the ecologically and commercially important role of mussels in coastal waters, a potential risk posed by neonicotinoids to this essential aquatic resource can be highlighted.

Experimental Zooprophylactic Institute of Sicily Via Gino Marinuzzi 3 90100 Palermo Italy

University of Messina Department of Chemical Biological Pharmaceutical and Environmental Sciences Viale Ferdinando Stagno d'Alcontres 31 98166 Messina Italy

University of Padova Department of Biology Via Ugo Bassi 58 B 35131 Padova Italy

University of South Bohemia in Ceske Budejovice Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses Research Institute of Fish Culture and Hydrobiology Zatisi 728 2 389 25 Vodnany Czech Republic

University of South Bohemia in Ceske Budejovice Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses Research Institute of Fish Culture and Hydrobiology Zatisi 728 2 389 25 Vodnany Czech Republic; University of Messina Department of Chemical Biological Pharmaceutical and Environmental Sciences Viale Ferdinando Stagno d'Alcontres 31 98166 Messina Italy

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Selected neonicotinoids and associated risk for aquatic organisms