Comparative ultrastructure of the cytoskeleton and nucleus of Distigma (Euglenozoa)

Although the ultrastructure of the pellicle is currently considered as a valuable tool for systematic assessments within euglenoids, comparative aspects at the genus level are largely lacking. Whereas species of the pigmented genus Euglena have been the focus of some comparative ultrastructural analyses, colourless taxa have been generally neglected. This study attempts to describe the cytoarchitecture of the non-pigmented euglenoid genus Distigma, with special emphasis on the pellicle and nucleus morphology of D. curvatum Pringsheim, D. elegans Christen, D. glabrum Pringsheim ex Ettl nom. nud. non D. glabrum Christen, D. gracile Pringsheim, D. proteus var. proteus Ehrenberg emend. Pringsheim, D. proteus var. longicauda Angeler and D. sennii Pringsheim. All taxa possess the typical plastic type of pellicle which allows for euglenoid movements. Interspecific variations in pellicular strip construction may explain differences in form and degree of "metaboly". Based on the results the taxonomic significance of pellicle and nucleus ultrastructure in the genus can be discussed. Finally, some remarks on obviously mislabelled cultures are given.