Effects of the antidepressant fluoxetine on the immune parameters and acetylcholinesterase activity of the clam Venerupis philippinarum

Fluoxetine is an antidepressant used worldwide for the treatment of depression and other psychological disorders. The occurrence of fluoxetine in aquatic environments has been demonstrated. However, there is a lack of information about the effects of fluoxetine on non-target species, such as bivalve molluscs. In the present study, the effects of fluoxetine on the immune parameters of the clam Venerupis philippinarum were evaluated for the first time. Clams were exposed to various sublethal concentrations of fluoxetine (0, 1, 5, 25, 125, 625 µg l-1) for 7 days, and the effects on the total haemocyte count (THC), the diameter and volume of haemocytes, haemocyte proliferation, Neutral Red uptake (NRU), lysozyme activity in cell-free haemolymph (CFH) and were evaluated. In addition, acetylcholinesterase (AChE) activity was measured in clam gills as a biomarker of neurotoxicity. A significant increase in THC values was observed in clams exposed to 25 µg l-1 compared with controls, whereas no significant variations were recorded in either the diameter or the volume of haemocytes. Haemocyte proliferation increased significantly in animals exposed to 25, 125 and 625 µg l-1 compared with controls. NRU decreased significantly in the haemocytes of clams exposed to 1 or 5 µg l-1, whereas NRU returned to control values in clams exposed to the highest fluoxetine concentrations tested (25 to 625 µg l-1). No significant alterations were observed in CFH lysozyme activity, whereas gill AChE activity decreased significantly in clams exposed to 1 or 5 µg l-1. Overall, the obtained results demonstrated that fluoxetine markedly affected immune parameters and AChE activity in clams.