Metabolic programming of zebra fish, Danio rerio uncovered. Physiological performance as explained by Dynamic Energy Budget Theory and life-cycle consequences of uranium induced perturbations

The aim of this dissertation is to characterize the toxicity of depleted uranium (U) on the metabolism of zebra fish, Danio rerio. The underlying hypothesis of this work is that effects of U show up as effects on the metabolism of the individual. Consequently, we characterized physiological performance using Dynamic Energy Budget (deb) theory since it is the only theory which simultaneously species ingestion, assimilation, growth, reproduction, maturation, maintenance and ageing over the whole life-cycle at varying food availability. Thus a deb model was built which quantifies and predicts how the physiological performance of zebra fish relates to food level (and temperature). We showed that development accelerates after birth until metamorphosis after which acceleration ceases. Furthermore, somatic maintenance costs are very high. A module specifying toxico-kinetics of U in a feeding, growing and reproducing individual was incorporated into the deb model. The model was then applied to toxicity data (from the literature or acquired during this thesis) in order to determine which processes are affected by U. Our results show that, from 0 nM onwards, U increases costs for growth and either increases somatic maintenance or decreases assimilation. We were unable to detect effects on maturation. A histological study showed that U alters histology of the gut wall and may perturb host-microbe homeostasis. By accounting for differences in initial conditions between individuals we were able to explain a number of seemingly contradictory results. The take home message is: observations on individuals should not be averaged for groups of individuals. (author)