p.Gly119Ser The nontarget amphipod populations have become resistant to Organophosphate and carbamate insecticides. The terrestrial application of pesticides has provided strong selective pressures to drive evolution in a nontarget, aquatic species
(Below N is a link to NCBI taxonomic web page and E link to ESTHER at designed phylum.) > cellular organisms: NE > Eukaryota: NE > Opisthokonta: NE > Metazoa: NE > Eumetazoa: NE > Bilateria: NE > Protostomia: NE > Ecdysozoa: NE > Panarthropoda: NE > Arthropoda: NE > Mandibulata: NE > Pancrustacea: NE > Crustacea: NE > Multicrustacea: NE > Malacostraca: NE > Eumalacostraca: NE > Peracarida: NE > Amphipoda: NE > Senticaudata: NE > Talitrida: NE > Talitroidea: NE > Hyalellidae: NE > Hyalella: NE > Hyalella azteca: NE
LegendThis sequence has been compared to family alignement (MSA) red => minority aminoacid blue => majority aminoacid color intensity => conservation rate title => sequence position(MSA position)aminoacid rate Catalytic site Catalytic site in the MSA MWCRYLVLALVFTLGTSALHDPLVVNTRKGKVKGKTVKTALGGEVDAWYS IPFAKPPVGDLRFRHPIPIDRWHDVKDATELPNSCWQTLDDFFGNFEGST MWNANTPMSEDCLYLSIIVPKPRPTNVPVLVWIYGGGFYSGTSSLEVYDY RTLADNQNVIIVAPHYRIASLGFLYMGTPDVPGNTGLFDQLMALEWIKDN IEFFGGNPNNITLMGESAGATSISMLLLSPLSRNLFSQAIMQSGSATVPW GIMSKKENMLRGQRLAEAVGCPTDMSNPSVVIDCLRSKNASELVNSETSN GVTDFPFVPIIDGAFFDKLPIEYLRNGDFKKCNILMGSNTEEGYWFIMYF LPSLFRREENVLITRAEFERSVRALFPYFNELILQAIMYQYTDWIDPEDG AKNRNAIDKMIGDYHFTCNVNEFAEYYSKSGNNVYMYYFKHRSSGSKWPK WTGVLHADEISFLFGQPLNPKYTTFTEVEQDLSRQMMTYWGNFIKTGNPS EGDHRSFAKTKWPLYSPATKEYLILSGEESGLGRGPRLKECAFWKSFLPQ LVKHSGEIWPVVK
Hyalella azteca are epibenthic amphipods that have developed resistance to pyrethroid and organophosphate insecticides due to single amino acid substitutions in the voltage-gated sodium channel and the acetylcholinesterase-1 gene, respectively. Aquatic systems are often contaminated with several different types of insecticides, therefore there is a possibility that H. azteca have also developed resistance to other classes of insecticides. The aims of the current study were to verify that pyrethroid- and organophosphate-resistant H. azteca have retained their resistance after being cultured in the absence of selective pressure for 5 years (Escondido Creek population) and 9 years (Mosher Slough population), to determine if these populations have cross-resistance to carbaryl (carbamate) and 4,4'-dichlorodiphenyltrichloroethane (DDT; organochlorine), and determine whether previous field exposure to fipronil (phenylpyrazole) and imidacloprid (neonicotinoid) caused resistance in cultured pyrethroid- and organophosphate-resistant H. azteca populations. Escondido Creek and Mosher Slough H. azteca populations both maintained high tolerances for bifenthrin due to L925I and I936F amino acid substitutions. Resistance was also found for chlorpyrifos in the Escondido Creek and Mosher Slough populations with lower genotype frequencies of the G119S substitution, indicating that additional factors may be responsible for organophosphate resistance in this study. Mosher Slough H. azteca were moderately resistant to DDT, and Escondido Creek and Mosher Slough H. azteca were moderately resistant to carbaryl, suggesting cross-resistance. No differences were observed in acute toxicity values across the three populations of H. azteca for fipronil and imidacloprid, and this is possibly due to the lack of exposure to toxic concentrations of these insecticides in the field and lack of similar modes of action to pyrethroids and organophosphates. Resistance is known to be associated with fitness costs that can place insecticide-resistant populations at risk for decline through decreased survival and reduced fecundity.
Organophosphate (OP) and carbamate (CM) insecticides are widely used in the United States and share the same mode of toxic action. Both classes are frequently documented in aquatic ecosystems, sometimes at levels that exceed aquatic life benchmarks. We previously identified a population of the nontarget amphipod, Hyalella azteca, thriving in an agricultural creek with high sediment levels of the OP chlorpyrifos, suggesting the population may have acquired genetic resistance to the pesticide. In the present study, we surveyed 17 populations of H. azteca in California to screen for phenotypic resistance to chlorpyrifos as well as genetic signatures of resistance in the acetylcholinesterase (ace-1) gene. We found no phenotypic chlorpyrifos resistance in populations from areas with little or no pesticide use. However, there was ~3- to 1,000-fold resistance in H. azteca populations from agricultural and/or urban areas, with resistance levels in agriculture being far higher than urban areas due to greater ongoing use of OP and CM pesticides. In every case of resistance in H. azteca, we identified a glycine-to-serine amino acid substitution (G119S) that has been shown to confer OP and CM resistance in mosquitoes and has been associated with resistance in other insects. We found that the G119S mutation was always present in a heterozygous state. Further, we provide tentative evidence of an ace-1 gene duplication in H. azteca that may play a role in chlorpyrifos resistance in some populations. The detection of a genetically based, adaptive OP and CM resistance in some of the same populations of H. azteca previously shown to harbor a genetically based adaptive pyrethroid resistance indicates that these nontarget amphipod populations have become resistant to many of the insecticides now in common use. The terrestrial application of pesticides has provided strong selective pressures to drive evolution in a nontarget, aquatic species.
