Ultrastructure of the reservoir and flagella in Phacus pleuronectes (Euglenophyceae)

The ultrastructure of the reservoir region of P.pleuronectes is described. Thin sections, ruthenium red staining, and shadow-cast preparations elucidate relationships and structural details of the flagella and flagellar hairs or mastigonemes. A heretofore undescribed structure in Phacus, the multitubular structure (MTS), with associated fibrillar projections, is reported, The MTS is located in the cytoplasm at the distal region of the reservoir near the contractile vacule. A coordinated function of the MTS and adjacent fibrillar projections is suggested. The occurrence of mastigonemes along the entire length of the emergent flagellum is suggested, in contrast to earlier reports of their presence only on that portion of the flagellum distal to the cytostome. The present investigation postulates also that the mastigonemes are bipartite, the thicker fibrous bases becoming modified distally into the classically described mastigonemes.