title: Mechanisms of resistance and cross-resistance to agrochemicals in the fairy shrimp Thamnocephalus platyurus (Crustacea: Anostraca).
abstract: Extensive pesticide usage in the Southern High Plains has led to the development of resistance in many pest species, as well as some non-target organisms. Thamnocephalus platyurus derived from agriculturally impacted watersheds are between two and three times less sensitive to commonly applied agrochemicals than T. platyurus from native grassland watersheds. Biological mechanisms that convey such resistance are currently unknown. This study identified the contribution of metabolic enzymes to T. platyurus pesticide resistance using the synergists piperonyl butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) to inhibit cytochrome P450s or hydrolases, respectively. Inhibition of cytochrome P450s and hydrolases partially restored cyfluthrin and DDT sensitivity in T. platyurus, suggesting other resistance inferring mechanism(s) were also involved. However, inhibition of hydrolases with DEF completely restored methyl parathion sensitivity in pesticide resistant T. platyurus. DDT resistance paralleled cyfluthrin resistance, but did not for methyl parathion resistance. These data suggest that the primary mechanism for the development of resistance to agrochemicals in T. platyurus is due to increased metabolic detoxification.
authors.affiliation: The Institute of Environmental and Human Health, Department of Environmental Toxicology, Texas Tech University, 1207 Gilbert Dr, Lubbock, TX 79416, USA. john.brausch@ttu.edu
authors.forename: John M
authors.initials: JM
authors.lastname: Brausch
authors.forename: Philip N
authors.initials: PN
authors.lastname: Smith
mesh_terms: D000818:Animals; D033202:Anostraca / Q000187:drug effects*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004351:Drug Resistance / Q000187:drug effects / Q000502:physiology*; D006867:Hydrolases / Q000378:metabolism; D008658:Inactivation, Metabolic / Q000502:physiology*; D007928:Lethal Dose 50; D006899:Mixed Function Oxygenases / Q000378:metabolism; D010574:Pesticide Synergists / Q000494:pharmacology; D010575:Pesticides / Q000378:metabolism / Q000633:toxicity*; D010882:Piperonyl Butoxide / Q000494:pharmacology; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity*
chemical_list: D010574:Pesticide Synergists; D010575:Pesticides; D014874:Water Pollutants, Chemical; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D006867:Hydrolases; D010882:Piperonyl Butoxide