Evaluation and improvements of a mayfly, Neocloeon (Centroptilum) triangulifer (Ephemeroptera: Baetidae) toxicity test method

J.M. Lazorchak, H. Haring, K. Wyatt, W. Thoeny, S. DeCelles, J. Miller, A. Dickinson, T.S. Schmidt, D.J. Soucek, D. Walters

Research output: Chapter in Book/Report/Conference proceedingConference contribution


A recently published test method for Neocloeon triangulifer assessed the sensitivities of larval mayªies to several reference toxicants (NaCl, KCl, and CuSO4). Subsequent exposures have shown discrepancies from those results previously reported. 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 vs. eggs held in long-term storage at 4°C, and (c) 1-day-old larvae from four different laboratory cultures (two USEPA, one USGS and one University of Illinois). Fifty percent lethal concentration (LC50, mg/L) and 25% inhibition concentra-tion (IC25, μm) point estimates were used to quantify survival and growth, respectively. Statistically significant differences in survival were found amongst all cohorts via sensitivity of mayªies at differing test initiation ages (LC50=616.56, 989.43, 1667.24), with survivorship positively correlating to age. No significant differences in growth could be elucidated between different aged treatments. Survival and growth of fresh 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 differ-ences were observed between stored cohorts. A comparison of fresh eggs from four different laboratory cultures showed no significant differences in survival or growth. To ensure consistent and sensitive test results we recommend continuing the use of 1-day-old larvae and freshly hatched eggs when using this species.
Original languageEnglish (US)
Title of host publicationSociety of Environmental Toxicology and Chemistry North America 36th Annual Meeting, 1-5 November 2015, Salt Lake City, Utah
StatePublished - 2015


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