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Evaluation and improvements of a mayfly, Neocloeon (Centroptilum) triangulifer (Ephemeroptera: Baetidae) toxicity test method - SETAC Europe 2016
Lazorchak, Jim, H. Haring, K. Wyatt, W. Thoeny, S. Decelles, J. Miller, A. Dickinson, M. Raby, T. Schmidt, D. Soucek, AND D. Walters. Evaluation and improvements of a mayfly, Neocloeon (Centroptilum) triangulifer (Ephemeroptera: Baetidae) toxicity test method - SETAC Europe 2016. SETAC Europe, Nantes, FRANCE, May 22 - 26, 2016.
This poster will present improvements in toxicity testing using the mayfly Neocloeon triangulifer. By making a few changes to the previously approved methods there will be more reliable and reproducible test results generated from future studies
A recently published test method for Neocloeon triangulifer assessed the survival and growth of larval mayflies exposed to several reference toxicants (NaCl, KCl, and CuSO4). Results were not able to be replicated in subsequent experiments. To identify potential sources of variability, the authors measured 7-day growth and survivorship in NaCl, using: (a) 1- vs. 3- vs. 5-day-old larvae, (b) 1-day-old larvae hatched from freshly collected eggs (not stored at cold temperatures) vs. eggs held in long-term storage at 4°C, and (c) 1-day-old larvae from five different laboratory cultures (two U.S. EPA, one USGS, one University of Illinois and one from University of Guelph). Fifty percent lethal concentration (LC50, mg/L) and 25% inhibition concentration (IC25, µm) point estimates were used to quantify survival and growth, respectively. Statistically significant differences in NaCl LC50s were observed among different ages of mayflies at test initiation (LC50=616.56, 989.43, 1667.24), with older organisms being less sensitive. No significant differences in growth could be elucidated between different aged treatments. Survival and growth of freshly collected eggs (LC50=701.27, IC25=626.56) differed significantly from eggs stored at 4°C for either three (LC50=394.13, IC25=424.47) or five (LC50=424.18, IC25=361.28) months, though no significant differences were observed between stored cohorts. A comparison of freshly collected eggs from 4 of the 5 different laboratory cultures tested do far showed no significant differences in survival or growth. Additional results will also be presented on larval age, storage, and laboratory source comparisons with KCl and CuSO4, and comparisons of freshly collected eggs vs 2 month old stored eggs at 10°C. To ensure consistent and sensitive test results we recommend continuing the use of 1-day-old larvae when using this species.