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Abstract

The body plan of every higher animal is formed in a series of tissue folding and migration events called gastrulation. At the end of gastrulation, the three tissue layers ectoderm, mesoderm and endoderm are defined. In addition to the formation of these tissue layers, the embryo of the fruit fly Drosophila melanogaster extends during gastrulation along its head-to-tail axis. During this process of germband extension, the embryo doubles the germband in size and folds it onto itself. Germband extension coincides at the future head and tail by invagination of the gut and is accompanied by the formation of transient folds in the head (cephalic furrow) and back (dorsal folds) of the embryo. Some of these events, like the formation of the posterior gut, provide support for germband extension. Other events such as invagination and rotation of the cephalic furrow, or anterior and posterior invagination of the dorsal folds coincide with germband extension dynamics in a spatial and temporal manner, but their function or relationship with respect to germband extension remains unknown. In my thesis I established tools for the qualitative and quantitative analysis of folds and the epithelium of the Drosophila embryo. These tools allowed me to address the putative function of these transient folds by quantitative analyses of whole mount time lapse recordings in the developing Drosophila embryo, giving me a new global picture of motion dynamics in the Drosophila embryo.