Some Contributions of Research on Early Teleost Embryogenesis to General Problems of Development

Abstract

A number of teleost eggs present outstanding advantages for the study of vertebrate development. Teleosts occur all over the world in both fresh and sea water of all degrees of salinity and often have long spawning seasons. Indeed, some species, such as the zebrafish (Brachydanio rerio), the medaka (Oryzias latipes), and the rosy barb (Barbus conchonius), can be induced to spawn year-round in the laboratory. Moreover, the eggs and embryos of teleosts are often unusually resistant to small environmental changes and thus will withstand much experimental manipulation. Although removal of the chorion is difficult in certain species (like Fundulus heteroclitus), it is easy in many others, such as the zebrafish, rosy barb, blennies, and gobies. Further, many species produce eggs of striking lucidity, so that cytokinesis, cell movement and form changes of individual cells can be observed directly and followed in the living embryo. And now, with new powerful means of marking cells by injecting non-toxic fluorescent macro-molecules, the lineage of cells may also be followed readily during early embryogenesis in these transparent embryos. Finally, because of the ease of propagation of some fish embryos throughout the year and their rapidity of development, sophisticated genetic studies of development can be pursued.