Microtubular cytoskeletons of the trophic cells of five eumycetozoans

Summary The trophic cells of the protostelids,Ceratiomyxella tahitiensis, Cavostelium apophysatum, Planoprotostelium aurantium, andClastostelium recurvatum, and the reduced myxomycete,Echinostelium bisporum, were examined with indirect immunofluorescence to determine the overall structure of the microtubular cytoskeletons of each type of cell. All five species have a distinct flagellar apparatus in the amoeboflagellate state, but they vary with respect to the presence of body microtubules, those microtubules which do not focus on the flagellar apparatus. The obligate amoebae ofC. tahitiensis, C. apophysatum andC. recurvatum all have extensive microtubular cytoskeletons, but each is unique to its respective species. The obligate amoeba ofC. tahitiensis has scattered microtubules which often describe curved paths. The microtubules never appear to focus on MTOCs. The microtubular cytoskeleton ofC. apophysatum consists of relatively straight, rigid appearing microtubules. Small subpopulations of these microtubules radiate from MTOCs near the nucleus. The obligate amoeba ofC. recurvatum has a cytoskeleton consisting of numerous microtubules which radiate from a perinuclear MTOC and fill the body of the cell. These results correlate well with earlier ultrastructural observations which suggest that the amoeboflagellate state is homologous in these mycetozoans and that the obligate amoebae, when present, are unique to the various lineages in which they appear.