Fish in behavior research: Unique tools with a great promise!

• Comparative behavioral neuroscience answers phenogenetic and phylogenetic questions.
• Study of new species increases translational relevance in biomedical research.
• Zebrafish strike a balance between practical simplicity and system complexity.
• Analysis of evolutionarily older species helps us find the core mechanisms.

Fish represent the most diverse class of vertebrates on Earth and also an unprecedented, but as of yet still largely untapped, resource for comparative analyses that can illuminate answers to questions about both how organisms work and how they evolved. The current review is a general discussion of some of the basic principles of why adding new species such as fish to the short list of biomedical model organisms (mainly the house mouse and the rat) has merit. In addition to the general points, it also reviews some questions about a newcomer, the zebrafish, which is rapidly gaining popularity in brain and behavior research. It discusses some examples demonstrating the advantages and disadvantages of the zebrafish mainly in the context of biomedical research. It is followed by other articles that further elaborate on these questions.