Reconstruction of the Flagellar apparatus in Ploeotia costata (Euglenozoa)and its relationship to other euglenoid flagellar apparatuses

The flagellar apparatus of Ploeotia costata Fanner and Triemer was reconstr ucted using serial sectioning and TEM. The flagellar apparatus is similar t o other euglenoids having two flagella arising from basal bodies connected by a striated fiber, and three asymmetrically arranged roots. The flagella emerge subapically from between the two ventral pellicle strips. The dorsal flagellum is 1/2 the body length and actively pulls the cell, while the ve ntral flagellum is twice the body length and drags along the substrate surf ace. The ventral and dorsal roots are on the opposite sides of their respec tive basal bodies, while the intermediate root is associated with the ventr al flagellum on the side closest to the dorsal basal body. The dorsal root lints the dorsal side of the reservoir and after giving rise to the dorsal band lines the right side of the reservoir/canal. The ventral and intermedi ate roots join at the reservoir forming the intermediate-ventral root. whic h Lines the left and ventral sides of the reservoir/canal. There was no evi dence of a microtubule-reinforced pocket in P. costata. Comparisons with Pl oeotia vitrea, Lentomonas applanatum, and related flagellar apparatuses led to the conclusion that the basic euglenoid flagellar structure is symplesi omorphic but with enough variation to be taxonomically diagnostic.