Trypanosoma brucei as a model system for flagellum structure and function studies. Artistic representation of the trypanosome, emphasizing the evolutionarily conserved character of the 9 + 2 flagellar axoneme, with various ciliated organisms representing the radial spokes. (Clockwise from top: Ciona intestinalis, Danio rerio, Drosophila melanogaster, Gallus gallus, Chlamydomonas reinhardtii, Homo sapiens, Caenorhabditis elegans, Mus musculus, and Asterias forbesi.) The paraflagellar rod, unique to trypanosomes, is not shown.