Phenotypic responses in caenorhabditis elegans following Chronic low-level exposures to inorganic and organic Compounds

Abstract

Responses of organisms to sub-lethal exposure of environmental stressors can be difficult to detect. We investigated phenotypic changes in the tissue of Caenorhabditis elegans via Raman spectroscopy, as well as survival and reproductive output when exposed to chronic low dose of exposure metals (copper, zinc or silver), an herbicide (diuron) and a pesticide (imidacloprid). Raman spectroscopy measures changes in phenotype by providing information about the molecular composition and relative abundance of biomolecules. Multivariate analysis was used to evaluate the significance of treatment phenotype segregation plots compared to controls. Dose-dependent responses were observed for copper, zinc, silver and diuron while imidacloprid exposure resulted in a small response over the tested concentrations. Concentrationdependent shifts in nematode biomolecular phenotype were observed for copper. Despite having a dose–dependent reproductive response, silver, diuron and imidaclorprid had inconsistent biological phenotype patterns. In contrast, there was a clear stepwise change between low concentrations (0.00625 - 0.5 mg/L) and higher concentration (1 – 2mg/L) of ionic zinc. The findings demonstrate that measuring phenotypic responses via Raman spectroscopy can provide an insight into the biomolecular mechanisms of toxicity. Despite the lack of consistency between survival and Raman-measured phenotypic changes, the results supports the effectiveness of Raman spectroscopy and multivariate analysis to detect sub-lethal responses of chemicals on whole organisms and to identify toxic effect thresholds.