Hemistasia phaeocysticola (Scherffel) comb. nov., Redescription of a Free-living, Marine, Phagotrophic Kinetoplastid Flagellate

We investigated a common, free living, marine, phagotrophic flagellate by light and electron microscopy. It has two heterodynamic flagella, a flexible cell shape and a pronounced apical rostrum. So far it was regarded as dinoflagellate and called Pronoctiluca phaeocysticola (Scherffel) Pavillard. Our investigation revealed, however, that it belongs to the bodonids (Kinetoplastida). The mitochondrium is of the polykinetoplastic type. The two flagella insert in a deep flagellar pocket and have a paraflagellar rod. The cytostome, the cytopharynx and the rostrum are supported by various cytoskeletal elements, the most prominent of which is a reinforced microtubular band. A distinct rod organ(= microtubular prism, nemadesm) has not been found. It has extrusomes of the “lattice tube” type. A distinct glycocalyx and a spiral groove of the cell body are absent. It fits the description of Hemistasia klebsii Griessmann. We regard both as con-specific and introduce the combination Hemistasia phaeocysticola (Scherffel) Elbrächter & Schnepf, comb. nov. The delimitation to other, similar organisms placed in various genera is discussed.