Different sensitivity to organophosphates of acetylcholinesterase and butyrylcholinesterase from three-spined stickleback (Gasterosteus aculeatus): Application in biomonitoring

Different cholinesterases from brain and body muscle of the fish three-spin ed stickleback (Gasterosteus aculeatus) were investigated concerning their potential use in the biomonitoring of organophosphate insecticides (OPs). S tickleback brain contained acetylcholinesterase (AChE) but no butyrylcholin esterase (BChE). Body muscle contained both AChE and BChE. In vitro, body m uscle BChE was three orders of magnitude more sensitive than brain or body muscle AChE to the OPs paraoxon and dichlorvos. In 1998, cholinesterase act ivities were recorded in stickleback from eight streams differing in pestic ide contamination. Automated on-site samplers that selectively collect wate r during runoff events were used to obtain water samples for pesticide anal ysis. The OP parathion was found in stream water sampled during runoff even ts in five cases. The variation of brain and body muscle AChE activity betw een streams was not related to water contamination by pesticides. Body musc le BChE was strongly decreased (>85%) in stickleback collected at all strea ms with previous parathion contamination events. A significant decrease in BChE (78%) occurred also, however, at one stream where other pesticides but no OPs were found. Because stickleback AChE and BChE differed strongly in their in vitro sensitivity and their response in the field, these enzymes s hould be considered separately in studies with fish.