title: Response and recovery of acetylcholinesterase activity in freshwater shrimp, Paratya australiensis (Decapoda: Atyidae) exposed to selected anti-cholinesterase insecticides.
abstract: The toxicity of carbaryl, chlorpyrifos, dimethoate and profenofos to the freshwater shrimp, Paratya australiensis was assessed by measuring acetylcholinesterase (AChE) inhibition after 96h exposures. Shrimp exposed to these pesticides exhibited significant AChE inhibition, with mortality in shrimp corresponding to 70-90% AChE inhibition. The sensitivity of P. australiensis to the four pesticides based on AChE inhibition can be given as chlorpyrifos > profenofos > carbaryl > dimethoate. Recovery of AChE activity was followed in shrimp after 96 h exposures to carbaryl, chlorpyrifos and dimethoate. Recovery after exposure to the carbamate pesticide carbaryl was more rapid than for the two organophosphorus pesticides, chlorpyrifos and dimethoate. The slow recovery of depressed AChE activity may mean that affected organisms in the natural system are unable to sustain physical activities such as searching for food or eluding predators. To investigate the ecological significance of AChE inhibition, chemotaxis behaviour was assessed in shrimp exposed to profenofos for 24h. Abnormal chemotaxis behaviour in the exposed shrimp was observed at concentrations representing 30-50% AChE inhibition. A clear relationship existed between the depression of AChE activity and observed chemotaxis responses, such as approaching and grasping the chemoattractant source. These results suggest that in vivo toxicity tests based on this specific biomarker are sensitive and present advantages over conventional acute tests based on mortality. Behavioural studies of test organisms conducted in conjunction with measurement of AChE inhibition will provide data to clarify the toxic effects caused by sublethal chemical concentrations of anti-cholinesterase compounds.
authors.affiliation: Centre for Environmental Contaminants Research, CSIRO Land and Water, PMB 2, Urrbrae 5064, SA, Australia. Anupama.Kumar@csiro.au
authors.forename: A
authors.initials: A
authors.lastname: Kumar
authors.forename: H
authors.initials: H
authors.lastname: Doan
authors.forename: Mary
authors.initials: M
authors.lastname: Barnes
authors.forename: J C
authors.initials: JC
authors.lastname: Chapman
authors.forename: R S
authors.initials: RS
authors.lastname: Kookana
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D012721:Carbaryl; D002633:Chemotaxis / Q000187:drug effects*; D004390:Chlorpyrifos; D002800:Cholinesterase Inhibitors / Q000032:analysis / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D033364:Decapoda / Q000187:drug effects* / Q000201:enzymology*; D004117:Dimethoate; D008401:Gas Chromatography-Mass Spectrometry; D007306:Insecticides / Q000032:analysis / Q000633:toxicity*; D063086:Organothiophosphates; D012680:Sensitivity and Specificity; D013021:South Australia; D013997:Time Factors; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D002800:Cholinesterase Inhibitors; D007306:Insecticides; D063086:Organothiophosphates; D014874:Water Pollutants, Chemical; C024273:profenofos; D000110:Acetylcholinesterase; D004390:Chlorpyrifos; D012721:Carbaryl; D004117:Dimethoate