Ultrastructure and identification of the predatory flagellateColpodella pugnax Cienkowski (Apicomplexa) with a description ofColpodella turpis n. sp. and a review of the genus

A flagellated predator of the chlorophyte algaDunaliella spp. was examined by light and electron microscopy. Although this predator had previously been identified as a species of the kinetoplastid genusBodo, the present study revealed the flagellate to be indistinguishable fromColpodella pugnax, the type-species for its genus. The flagellate lacks a kinetoplast, a microtubule supported cytopharynx and paraxial rods in the flagella — characters universally found in kinetoplastid flagellates. The cell has mitochondria with vesicular cristae. Multiple membranes surround the cell and are underlain by longitudinal microtubules not originating from the flagellar region. Most notably, the flagellate has micropores and an apical complex including a conoid, sacculate rhoptries and, apparently, a polar ring. This study hs confirmed thatColpodella is the genus with free-living species most closely related to the apicomplexan parasites (i.e. the “Euapicomplexa” andPerkinsus). No unambiguous synapomorphy supports an “apicomplexan parasites” clade: Inclusion ofColpodella is necessary to secure the Apicomplexa as a monophyletic (=holophyletic) taxon. A new family, the Colpodellidae, is erected for this genus. Colpodella turpis, a previously undescribed species that also consumesDunaliella spp., was isolated from the same samples asC. pugnax. A diagnosis for this species is presented together with a brief review of the genus, in which we recognise seven species. The generic namesAlphamonas Alexeieff,Nephromonas Droop andDingensia Patterson & Zolffel are rendered into synonomy withColpodella.