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 r egarded as dinoflagellate and called Pronoctiluca phaeocysticola (SCHE RFFEL) PAVILLARD. Our investigation revealed, however, that it belongs to the bodonids (Kinetoplastida). The mitochondrium is of the polykin etoplastic type. The two flagella insert in a deep flagellar pocket an d have a paraflagellar rod. The cytostome, the cytopharynx and the ros trum are supported by various cytoskeletal elements, the most prominen t 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 kle bsii GRIESSMANN. We regard both as conspecific and introduce the combi nation Hemistasia phaeocysticola (SCHERFFEL) ELBRACHTER & SCHNEPF, com b. nov. The delimitation to other, similar organisms placed in various genera is discussed.