The fish embryo as a model for AOP development

Abstract

Fish are routinely used for evaluating aquatic toxicity to vertebrates to set environmental quality standards. Tests using early life-stages of fish are more costefficient compared to tests using adult fish while maintaining the physiological relevance of a vertebrate whole-organism test system. Ethical considerations are also a driver for the use of fish embryos since they are considered alternative testing models during the early stages of development. Additionally, both in human and environmental toxicology there is a strong global interest in increasing the use of mechanistic information to support hazard assessment. The AOP (adverse outcome pathway) approach offers an interesting framework for developing mechanistically-based alternative testing methods using fish embryos. Once developed, AOPs can facilitate the identification of assays targeting key events, which have high predictive value for an adverse outcome of interest. In this chapter we first discuss what kind of information on the general biology and physiology of a fish species is important in order to use the embryonic life stage of that species as a model for AOP development, including aspects such as endocrinology, reproduction strategies, availability of genomic information, transgenic lines, and biotransformation capacity during embryonic development. Secondly, we provide an overview of strategies and examples of AOP development using fish embryos. In this context, we discuss the application of an iterative AOP development cycle, development of Fish Early Life-Stage (FELS) AOPs for developing alternative strategies for chronic toxicity testing, development of AOP networks, and development of fish AOPs for endocrine disruption.