Protistology 2 (2) 85–95 (2001) The ultrastructure of Procryptobia sorokini (Zhukov) comb. nov. and rootlet homology in kinetoplastids
Alexander O. Frolov, Serguei A. Karpov and Alexander P. Mylnikov
Zoological Institute, Russian Academy of Sciences, St. Petersburg, Russia
Summary
The ultrastructure of a marine, free-living, heterotrophic kinetoplastid Procryptobia sorokini, was investigated with special attention to the
cytoskeletal structures. The flagellates have a typical eukinetoplastidal mitochondrion, 2 heterodynamic flagella and all other kinetoplastid
characters. The basal body of the anterior flagellum nucleates one dorsal microtubular rootlet, and the basal body of recurrent flagellum gives
rise to the ventral rootlet. The cytostome-cytopharyngeal complex is supported by 3 microtubular bands. One band (mtr) is derived from the
dorsal rootlet, and other two arise from the preoral crest. The recurrent flagellum adheres to the cell surface, with specialised contacts of the
"macula adherens" type similar to those found in trypanosomes. This species described earlier as Bodo sorokini (Zhukov, 1975) is
transeferred into the genus Procryptobia Vickerman, 1978, because of adherent recurrent flagellum and body shape characters. This is the
first strong evidence that biflagellated kinetoplastids have 2 microtubular rootlets, which are homologous with those in all investigated species
of bodonids and cryptobiids. These kinetoplastids contain the most complete set of these structures. Their rootlets have both the same
orientations and a similar number of microtubules in different kinetoplastids. Their derivatives occur in all kinetoplastids with the exception of
trypanosomatids, where the reduction of the posterior flagellum leads to the complete reduction of the ventral rootlet and structures associated
with it.
Key words: Procryptobia sorokini, kinetoplastids, bodonids, cryptobiids, ultrastructure, rootlet homology
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