Phylogenetic significance of the flagellar apparatus in protostelids (Eumycetozoa).

The ultrastructure of the flagellar apparatuses of four species of protostelids is described. All four species have the same three major groups of rootlet microtubules in common, microtubule arrays (MTA) 2, 3, and 4. Variation is found in the number of centrioles per flagellar apparatus, presence or absence of two other microtubule arrays, MTA 1 and MTA 5, types of connectives linking the centrioles to the MTAs, nature of the transitional elements of the flagella, and the association of the flagellar apparatus with the nucleus. It is concluded on the basis of this study and comparison with earlier studies on protostelids, myxomycetes, and other amoeboflagellates that the flagellate species of protostelids are monophyletic. The significance of this to the phylogeny of protostelids and related mycetozoans is discussed.