C. elegans is well established as a model system to study animal development. It has a short lifespan, and can easily be handled in large numbers. It has a small number of cells and develops through a series of nearly invariant divisions. This made it possible to describe the entiry C. elegans cell lineage, from the one cell embryo to the adult. C. elegans is transparent, which enables us to follow its development by microscopy, and a powerful genetic toolkit exists to study gene function.
For systems biology purposes, an important benefit of using C. elegans is that the genome sequence and annotations are of the highest quality available for any multicellular organism. Accurate gene predictions aid the large-scale cloning of genes, and are essential for the identification of proteins by mass spectrometry, which relies on a database of predicted protein sequences. In addition, C. elegans has smaller protein families than mammals. For example, humans have 3 different PAR6 genes, and 7 DLG family members, compared to a single family member each in C. elegans. As fewer proteins are involved, a complete interaction map is easier to obtain.
The nematode C. elegans. Image of a C. elegans adult taken under high magnification with Nomarski DIC optics (click to enlarge).