Ultrastructure and phylogeny of colpodellids (Colpodellida, Alveolata)

The structure of cells of the predatory flagellates Colpodella pseudoedax and C. unguis was studied. The cell was found to contain two heterodynamic flagella, three-membrane pellicle, micropores, subpellicular microtubules, microtubular open conoid, roptries, micronemes, extrusive organelles (trichocysts), and mitochondria with tubular cristae. Upon discharging, trichocysts form cross-striated bands. The thin-walled cylinder lies in the transitional zone of the flagella. Cells reproduce by means of longitudinal binary fission. The similarities between given species and other colpodelids and such between perkinsea, sporozoans, and dinoflagellates are discussed.