HEJNOL, A.*; SCHNABEL, R.; Technische Universit�t Braunschweig, Spielmannstr. 7, Germany: Comparative developmental studies using 4D-microscopy

The development of an organism occurs in space and time and is thus a 4-dimensional process. Here we present a microscope system, originally developed to analyze cell lineage mutants of the nematode Caenorhabditis elegans. This 4D-microscope system (3D-timelapse) can be used to record the entire development of an embryo and to analyze in detail cell cleavage, cell migration, cell death (apoptosis), and cell differentiation during development. The digital system is composed of three main parts: a motorized microscope equipped with a video camera, a control-software, and a database, SIMI�Biocell, to facilitate the analysis of the recordings and permit the documentation of the observations. We adopted this 4D-microscopy technique for analysis of small embryos in order to fill gaps in the description of development of diverse organisms, which are not accessible via labeling techniques of single blastomeres with fluorescent dyes. We used the technique to describe and reinvestigate the development of tardigrades, acoels, rotifers and gastrotriches, and have gained new insights about the evolution of developmental processes and the phylogenetic relationships between these taxa.