Are standard test species still relevant? A comprehensive assessment of <i>Daphnia pulex</i> reared in laboratory and wild environments and their responses to organic ultraviolet filters

The establishment of laboratory-based species has facilitated the standardization of biological research methods; however, the stable culturing conditions of laboratories are dissimilar to the dynamic conditions of natural environments, potentially influencing fundamentally different research outcomes between laboratory and wild populations. This study sought to compare the toxicity of ultraviolet filters (UVFs) avobenzone, octocrylene, and oxybenzone to laboratory and wild populations of Daphnia pulex, while also testing the effects of culturing both populations in either laboratory or lake water in 48 hr and 21 day toxicity tests. Both daphnid populations demonstrated poor performance when cultured in nonancestral waters for three generations (i.e., laboratory Daphnia in lake water or wild Daphnia in laboratory water), including 25% decreased reproduction in control treatments and ≥ 50% mortality to most UVF treatments. Toxicity varied in each population cultured in ancestral waters; laboratory D. pulex were more sensitive to 30.7 μg/L of avobenzone and 18.8 μg/L of oxybenzone (> 25% greater mortality, ≥ 20% decreased reproduction vs. wild daphnids), whereas wild D. pulex were more sensitive to 25.6 μg/L of octocrylene (30% decreased mortality, 44% decreased reproduction vs. laboratory daphnids). These results demonstrate that Daphnia populations can deviate after decades of isolation, highlighting the challenges of relating laboratory-generated data to field results. In addition, culture water greatly affected daphnid performance during experimentation, potentially leading to misinterpreted results when studying wild organisms. This research highlights the importance of understanding how laboratory and wild organisms can differ, so that research modeling environmental outcomes can be applied in an appropriate context.