Structural characterization of Eutreptia (Euglenophyta). III. Flagellar structure and possible function of the paraxial rods

Abstract The flagellar paraxial rods of the motile unicellular euglenoid flagellate Eutreptia pertyi Pringsheim (Euglenophyta) are highly ordered and differentiated structures. In the dorsal flagellum (F1) the rod (PAR1) is composed of one predominant substructural component, the oblique filaments that are arranged in complementary axes that give the rod a lattice-like appearance. In the ventral flagellum (F2), the rod (PAR2) is composed of three major substructural components: horizontal, longitudinal and oblique filaments organized into trigonal-hexagonal ‘unit cells’ that collectively impart a paracrystalline, plate-like appearance to the rod. The organization of paraxial rod subcomponents appears to be related to the position and organization of flagellar mastigonemes. The relatively small size and whorled shape of PAR1, the complementary axes of the oblique filaments and the helical arrangement of some flagellar mastigonemes are related to the rapid, helical waveform of the dorsal flagellum. Converse...