UMB 3: Toxicity Assessment of Ionizing Radiation in Daphnia Magna and Chlamydomonas Reinhardtii

Objective 

Provide relevant data for comparison of cross-species sensitivity to ionizing (gamma) radiation and multiple stressors in the freshwater crustacean Daphnia magna and the microalgae Chlamydomonas reinhardtii. A combination of molecular, cellular and functional responses will be assessed to characterize the toxicity to both species. The data generated will be used to identify key factors that drive species sensitivity to the different stressors and identify molecular targets and relevant toxicity pathways that may give rise to adverse effects. Experimental and theoretical data gathered will be used to develop a network of Adverse Outcome Pathways (AOPs) for multiple stressors on basis of Mode of Action (MoA) and adverse effect information.

Methods

D. magna and C. reinhardtii were exposed to gamma radiation (0.4 – 100 mGy/h and 0.4 – 1500 mGy/h, respectively) and exposure (ROS formation), early gene and functional (gene expression, lipid peroxidation, DNA damage, photosynthetic activity), and adverse effects (growth, reproduction, survival) determined by a suite of effects and response analysis.

Results

Results obtained for D. magna revealed multiple modes of action (MoA) after short-term exposure. Oxidative stress in the form of reactive oxygen species (ROS) formation and DNA damage was detected after 24h and 48h exposure, especially at higher doses. Gene expression patterns showed dose-dependent transcriptional alterations in D. magna after 24h exposure, with differentially expressed genes identified at low and high dose rates. Long-term alterations in fecundity (brood size, hatching time, molting and mortality) were also observed after 48h exposure. As seen for D. magna, a dose-dependent increase in ROS formation and alterations in photosystem performance was detected in C. reinhardtii after 6h exposure to gamma radiation.

Project Manager: Tânia Gomes