A COMPARISON OF PARAXIAL RODS IN THE FLAGELLA OF EUGLENOIDS AND KINETOPLASTIDS

Paraxial rods (PARs) are consistent features of most euglenoid and kinetoplastid flagella. This comprehensive comparison of PAR substructure in representative genera from both groups shows that there are diagnostic differences in PAR structure in the emergent flagella and that there are strong similarities between comparable flagella of different organisms, regardless of taxonomic affinity. The non-emergent flagellum of advanced euglenoids lacks a PAR, and the most elaborate structure is found in the trailing or recurrent flagellum of phagotrophic euglenoids and trypanosomatids. Based on PAR structure, the single emergent flagellum of the trypanosomes is most similar to the recurrent or ventral flagellum of the bodonids and euglenoids. The basic structural organization of the PAR in a given flagellum is the same: whorled/lattice-like in the dorsal or anterior flagellum, and plate-like/paracrystalline in the ventral or recurrent flagellum. The strinking similarities in PAR structure, together with other morphological and molecular data, provide further support for the hypothesized phylogenetic relationship between the euglenoids and kinetoplastids.