Insecticides resistance in marine invertebrates: an evolutionary adaptation for a successful colonization?

Organophosphate insecticides (OP), used in agricultural pest control and highly released in the aquatic environments might cause serious neurotoxic effects in non target species i.e. marine invertebrates. Recently, much attention has been devoted worldwide towards the invasive capacities of several aquatic invertebrates which, in some cases, represent serious ecological and economical threats. The invasive capacities of a pest species has often been related to its ecological plasticity and high intrinsic genetic variability but which role might have molecular and cellular mechanisms generally known as an organism’s response to stress? In the present study, three Mediterranean and one Antarctic filter-feeders (bivalves and polychaetes) were in vitro exposed to OPs and the activity of cholinesterases (ChEs), commonly inhibited by these chemicals were measured. All species, including the Antarctic scallop, showed low sensitivities to DFP, fenitrothion and azamethyphos (IC50: 103 –104 M) in line with the documented presence of OP-resistant forms among bivalve molluscs. The observed resistance in the Antarctic scallop seems to confirm an evolutionary adaptation of bivalves and might suggest a common genetic origin. This common OP resistance seems also to suggest a great adaptability of these species also in colonising non native environments such as the case of the polychaete sabellid and the Mediterranean mussel.