Classroom Explorations: Characteristics of Life
The zebrafish, Danio rerio, breeds year-round and produces hundreds of clear-shelled eggs with the developing embryos easily visible inside. The embryos develop from single cells to swimming fish in about two days. The visibility and speed of zebrafish embryonic development allow scientists to observe the growth of organs in very young embryos.
This video shows development from the single-cell stage to hatching. (The elapsed time is about 48 hours.)
Fertilized zebrafish eggs were mounted in fresh water between a slide and coverslip using a silicon rubber spacer. Images were taken at room temperature on an inverted compound microscope using a 10x DIC objective and digital camera.