Some recent publications of interest to members
of the HAAG include the following:
THE COMMON ECOTOXICOLOGY LABORATORY STRAIN OF HYALELLA AZTECA IS GENETICALLY DISTINCT FROM MOST WILD STRAINS SAMPLED IN EASTERN NORTH AMERICA
KALEY MAJOR, DAVID J. SOUCEK,* ROSANNA GIORDANO, MARK J. WETZEL, and FELIPE SOTO-ADAMES
Illinois Natural History Survey, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA
Abstract: The amphipod Hyalella azteca is commonly used as a model for determining safe concentrations of contaminants infreshwaters. The authors sequenced the mitochondrial cytochrome c oxidase subunit I (COI) gene for representatives of 38 populations ofthis species complex from US and Canadian toxicology research laboratories and eastern North American field sites to determine theirgenetic relationships. With 1 exception, all US and Canadian laboratory cultures sampled were identified as conspecific. In 22 wildpopulations spanning 5 US states and 1 Canadian province, the commonly occurring laboratory species was found only in northernFlorida, USA. Therefore, the diversity of the H. azteca species complex detected in the wild is not accurately represented in NorthAmerican laboratories, questioning the reliability of H. azteca cultures currently in use to accurately predict the responses of wildpopulations in ecotoxicological assays. The authors also examined the utility of different COI nucleotide fragments presently in use todetermine phylogenetic relationships in this group and concluded that saturation in DNA sequences leads to inconsistent relationshipsbetween clades. Amino acid sequences for COI were not saturated and may allow a more accurate phylogeny estimate. Hyalella azteca iscrucial for developing water-quality regulations; therefore, laboratories should know and standardize the strain(s) they use to confidentlycompare toxicity tests across laboratories and determine whether they are an appropriate surrogate for their regions.
Environ Toxicol Chem 2013;32:2637–2647. # 2013 SETAC
Multiple origins of pyrethroid insecticide resistanceacross the species complex of a nontarget aquatic crustacean, Hyalella azteca
Donald P. Westona,1, Helen C. Poynton b, Gary A. Wellborn c, Michael J. Lydy d, Bonnie J. Blalock b, Maria S. Sepulveda e,and John K. Colbourne f
a Department of Integrative Biology, University of California, Berkeley, CA 94720; bSchool for the Environment, University of Massachusetts, Boston, MA02125; cDepartment of Biology, University of Oklahoma, Norman, OK 73019; dCenter for Fisheries, Aquaculture and Aquatic Sciences, Southern Illinois University, Carbondale, IL 62901; eDepartment of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907; and fThe Center for Genomics and Bioinformatics, Indiana University, Bloomington, IN 47405
Abstract: Use of pesticides can have substantial nonlethal impacts on nontargetspecies, including driving evolutionary change, often withunknown consequences for species, ecosystems, and society. Hyalella azteca, a species complex of North American freshwater amphipods, is widely used for toxicity testing of water and sediment and has frequently shown toxicity due to pyrethroid pesticides.We demonstrate that 10 populations, 3 from laboratory cultures and 7 from California water bodies, differed by at least 550-fold in sensitivity to pyrethroids. The populations sorted into four phylogenetic groups consistent with species-level divergence. By sequencing the primary pyrethroid target site, thevoltage-gated sodium channel, we show that point mutations and their spread in natural populations were responsible for differences in pyrethroid sensitivity. At least one population had both mutant and WT alleles, suggesting ongoing evolution of resistance. Although nonresistant H. azteca were susceptible to the typical neurotoxic effects of pyrethroids, gene expression analysis suggests the mode of action in resistant H. azteca was not neurotoxicity but was oxidative stress sustained only at considerably higher pyrethroid concentrations. The finding that a nontarget aquatic species has acquired resistance to pesticides used only onterrestrial pestsis troublingevidence of the impact of chronic pesticide transport from land-based applications into aquatic systems. Our findings have far reaching implications for continued uncritical use of H. azteca as a principal species for monitoring and environmental policy decisions.
Effect of test duration and feeding on relative sensitivity of genetically distinct clades of Hyalella azteca
David J. Soucek • Amy Dickinson • Kaley M. Major •
Abigail R. McEwen
Ecotoxicology (2013) 22:1359–1366
Abstract: The amphipod Hyalella azteca is widely used inecotoxicology laboratories for the assessment of chemicalrisks to aquatic environments, and it is a cryptic species complex with a number of genetically distinct strains found in wild populations. While it would be valuable to note differences in contaminant sensitivity among different strains collected from various field sites, those findings would be influenced by acclimation of the populations to local conditions. In addition, potential differences in metabolism or lipid storage among different strains may confound assessment of sensitivity in unfed acute toxicity tests. In the present study, our aim was to assess whether there are genetic differences in contaminant sensitivity among three cryptic provisional species of H. azteca. Therefore, we used organisms cultured under the same conditions, assessed their ability to survive for extended periods without food, and conducted fed and unfed acute toxicity tests with two anions (nitrate and chloride) whose toxicities are not expected to be altered by the addition of food. We found that the three genetically distinct clades of H. azteca had substantially different responses to starvation, and the presence/absence of food during acute toxicity tests had a strong role in determining the relative sensitivity of the three clades. In fed tests, where starvation was no longer a potential stressor, significant differences in sensitivity were still observed among the three clades. In light of these differences in sensitivity, we suggest that ecotoxicology laboratories consider using a provisional species in toxicity tests that is a regionally appropriate surrogate.