EMBRYOLOGY AND GENETICS OF THE ZEBRAFISH, BRACHYDANIO-RERIO

A combination of approaches in embryology and genetics is necessary for our understanding of vertebrate development. The zebrafish is a simple vertebrate with many features that facilitate the study of development. Embryos are easily accessible at all stages and can be produced in large numbers. They develop rapidly; embryos hatch at two days, and most morphological features of the adult are visible at seven days. Most importantly, genetic methods developed to obtain haploid or gynogenic offsprings and lines of transgenic animals provide additional advantages for using zebrafish for the study of development. These methods are summarized here, along with a few studies in which the zebrafish is used as a model to address questions such as embryonic cell fate determination and the specificity of motoneural connection. These studies emphasize the importance of the availability of mutant embryos in which specific aspects of development are perturbed. Finally, a high degree of conservation exists between the zebrafish and distantly related vertebrate species in genes that are thought to be involved in developmental processes. This enhances the attractiveness of the zebrafish as a simple model of our own development.