Systematics of the enigmatic kathablepharids, including EM characterization of the type species, Kathablepharis phoenikoston, and new observations on K. remigera comb.nov.

The colorless flagellate Kathablepharis has consisted of five species based on light microscopic studies, and the ultrastructure of the type species, Kathablepharis phoenikoston, is described for the first time. The heterotrophic, marine flagellate Leucocryptos consisted of two species, but additional ultrastructural details for one of these, Kathablepharis remigera comb. nov. (= Leucocryptos remigera Vørs), indicates that it should be transferred to Kathablepharis. The cellular structure of these two species is similar to previously studied kathablepharids. However, there is variation in the feeding apparatus and cytoskeleton. The feeding apparatus of both species has a cytostome, a cytostomal ring, and cytopharyngeal rings. The cytoskeleton consists of inner microtubular arrays and outer or sub-pellicular microtubular arrays. In addition, several features of the flagellar apparatus are described for K. phoenikoston and K. remigera. The ultrastructure of these two species is compared with other kathablepharids to evaluate their taxonomy and phylogeny. We classify Kathablepharis and Leucocryptos in the family Kathablepharididae incertae sedis.