Zebrafish in context: Uses of a laboratory model in comparative studies

With the recent interest in the reintegration of evolutionary and developme ntal biology has come a growing need for understanding the phylogenetic rel ations and degree of generality of the model organisms upon which we rely s o heavily. In.vertebrate biology the zebrafish Danio rerio has become a par adigmatic system for studies at levels of organization. from molecular to i nterspecific. Studies of model systems in development are often techniques- driven rather than questions-based; however, informative hypotheses for dev elopmental research can be derived from phylogenetic: distributions of char acters. With some understanding of how general the characters of interest a re, a thoughtful comparison of the requirements of the questions with the l ists of available embryos, reagents, and protocols can guide choices of new vertebrate models. We describe here the phylogenetic placement of zebrafis h within the vertebrate world and discuss how generally observations on zeb rafish can be taken to apply. We outline a practical protocol for investiga ting development in a comparative context, illustrated with an example from an ongoing study of teleost tail hn evolution. The principles and procedur es presented here apply equally well to any comparative study with an inter est in evolution, at any level of phylogeny from intraspecific studies to c omparisons across phyla. (C) 1999 Academic Press.