A Re-Evaluation of Chironomid Deformities as an Environmental Stress Response: Avoiding Survivorship Bias and Testing Noncontaminant Biological Factors

Abstract

Larval deformities have been observed in chironomids, and are thought to be associated with aquatic contaminant exposure. However, in laboratory assays, deformities have not been linked with contaminants in the absence of potential confounding variables including mortality, which introduces a survivorship bias. There is also a paucity of data on noncontaminant causes. In addition, power analyses are rarely undertaken, meaning that effect sizes detectable are usually uncertain. We therefore aimed to clarify factors associated with deformities, by running survivorship bias–free (i.e., sublethal) assays, assessing contaminant (copper and imidacloprid) and noncontaminant (malnutrition) stressors..