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The effects of continuous diazinon exposure on growth and reproduction in Japanese medaka using a modified Medaka Extended One Generation Reproduction Test (MEOGRT)
Citation:
Flynn, K., D. Lothenbach, F. Whiteman, D. Hammermeister, J. Swintek, M. Etterson, AND R. Johnson. The effects of continuous diazinon exposure on growth and reproduction in Japanese medaka using a modified Medaka Extended One Generation Reproduction Test (MEOGRT). ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY. Elsevier Science Ltd, New York, NY, 162:438-445, (2018). https://doi.org/10.1016/j.ecoenv.2018.06.088
Impact/Purpose:
The manuscript presents the use of a modified version of the EPA’s Medaka Extended One Generation Reproduction Test (MEOGRT) to describe the effects of diazinon on long-term survival, growth, and reproduction in this fish species. Diazinon exposure in the low to mid- ug/L concentration range and lasting for the entire lifecycle of the fish reduced growth and reproductive output. In addition, the manuscript describes the advantages of additional growth measurements to better define the growth trajectories of exposed fish.
Description:
The Medaka Extended One Generation Reproduction Test (MEOGRT) is part of the U.S. Environmental Protection Agency’s (USEPA) Endocrine Disruptor Screening Program (EDSP) designed to characterize the potential adverse effects to fish of a chemical through endocrine disruption. As such, the MEOGRT focuses primarily on adverse effects to reproduction while collecting some information regarding effects on growth, survival, and endocrine-related endpoints. However, the risk assessment process for fish, as mandated by legislation such as Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) or the Toxic Substances Control Act (TSCA), could benefit from a more detailed assessment of effects on growth. Typically, fish growth data in support of risk assessment is obtained from full life-cycle tests or early life stage tests using the fathead minnow. As an alternative to these tests, a modified MEOGRT was conducted to assess the effects of diazinon on the various parameters measured in the MEOGRT. Diazinon is an organophosphate insecticide that is detected in the environment and whose efficacy is a result of inhibition of the acetylcholine esterase enzyme at neuromuscular junctions and synapses of the nervous system. Diazinon at 2.9, 5.2, 10.3, 19.8, and 40.2 ìg/L was tested with the MEOGRT protocol, and the lowest observable effect concentrations of 2.9 ìg/L for fecundity and 5.2 ìg/L for growth were determined. Also, additional growth measurements were added to the MEOGRT protocol to more robustly define growth and its impacts on reproductive performance. Size starting at the first measurement day, 21 days post-fertilization, and continuing through the duration of the test was reduced with exposure to 5.2 ìg/L and above, and asymptotic size predicted from the growth modeling was reduced at 10.3 ìg/L and above.
URLs/Downloads:
DOI: The effects of continuous diazinon exposure on growth and reproduction in Japanese medaka using a modified Medaka Extended One Generation Reproduction Test (MEOGRT)