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Do Daphnia magna and Ceriodaphnia dubia acute and chronic tests show equitoxic results? (presentation)
Citation:
Connors, K., T. Norberg-King, J. Brill, M. Barron, AND S. Belanger. Do Daphnia magna and Ceriodaphnia dubia acute and chronic tests show equitoxic results? (presentation). SETAC Europe virtual meeting, Duluth, MN, May 03 - 07, 2020.
Impact/Purpose:
This abstract shows that while it is important to consider the relative sensitivity of aquatic invertebrate species and how the species sensitivity may alter an environmental risk assessment, it is equally important to understand the sensitivity variation that is already contained within the standard regulatory assays. This evaluation of cladoceran interspecies modeling demonstrates similar sensitivity for Daphnids and C. dubia and the interchangeability of these taxa is recommended for chemical testing. This is the basis for proposing the C. dubia method for an OECD method.
Description:
Environmental risk assessments are typically based on acute and chronic toxicity data derived from only a handful of standard model organisms. Some standard regulatory assays limit the species in scope, others like the OECD 203 acute fish assay can be considered valid if one of seven recommended species are tested. While it is important to consider the relative sensitivity of other species and how this may alter an environmental risk assessment, it is equally important to understand the sensitivity variation that is already contained within the standard regulatory assays. The OECD 202 Acute Daphnia Immobilization Toxicity Test requires the use of Daphnia magna or another “suitable Daphnia species (e.g., Daphnia pulex).” At present, the daphnid species, Ceriodaphnia dubia, is not considered a standard test species for chemical registration in Europe despite the availability of ISO, USEPA, ASTM, Environment Canada standard acute and chronic test methods and its wide use and acceptance in other countries. Previous comparative work by Versteeg et al. (1997) suggests that D. magna, D. pulex, and C. dubia are acutely equi-sensitive. Here, we employ a big data approach to critically evaluate the comparative species sensitivity between D. magna and D. pulex and contrast that to the similar species sensitivity of D. magna and C. dubia. These big data approaches will then be contrasted against the smaller, more curated web-ICE regressions. A total of 207 chemicals that had both D. magna and D. pulex acute toxicity data were identified (5,443 studies). This orthogonal regression has a slope of 0.881 and an intercept of 0.484. As both D. magna and D. pulex are accepted OECD 202 standard test species, this inherent biological difference in sensitivity is accepted under the regulatory guidelines. A total of 193 chemicals that had both D. magna and C. dubia toxicity data were identified (5,465 studies). The orthogonal regression for the acute toxicity studies has a slope of 0.919 and an intercept of 0.599. The relative species sensitivity differences between D. magna and D. pulex and D. magna and C. dubia are of the same magnitude and have nearly identical slopes. D. magna and C. dubia chronic toxicity (83 chemicals, 1062 entries), also showed similar sensitivity with a slope of 0.841 and intercept 0.355. Interspecies modeling demonstrates similar sensitivity for Daphnids, and C. dubia and the interchangeability of these taxa is recommended for chemical testing.