Malawimonas jakobiformis n. gen., n. sp. (Malawimonadidae fam. nov.): a Jakoba-like heterotrophic nanoflagellate with discoidal mitochondrial cristae.

Charles J. O'Kelly

Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, Maine, USA

Thomas A. Nerad

Protistology Department, American Type Culture Collection, Manassas, Virginia, USA

Journal of Eukaryotic Microbiology 46: 522-531.

The name Malawimonas jakobiformis n. gen., n. sp., is created for a bacterivorous heterotrophic nanoflagellate isolated from the Malawi shore of Lake Nyasa (eastern Africa). Trophic stages observed were anteriorly biflagellate and naked. The posterior flagellum of a trophic cell resided in a prominent groove on the ventral surface, and bore a conspicuous vane. A Golgi dictyosome and a mitochondrion with discoidal cristae were present anterior to the nucleus. The kinetid consisted of two short, slightly separated basal bodies, four microtubular roots, and associated fibers and bands. The three microtubular roots associated with the posterior basal body were associated with the ventral groove, while the single root associated with the anterior basal body gave rise to secondary cytoskeletal microtubules. Dividing cells became rounded, with persistent flagella. Cysts were uninucleate, and had thin organic walls without clearly differentiated apertures or ornamentation but with conspicuous attachment pads. Kinetid elements were present within cysts. On the basis of microscopical features, especially those of the kinetid, the nearest relatives of M. jakobiformis are the mitochondrial "jakobid" protists (families Histionidae and Jakobidae) and the amitochondrial retortamonads. Malawimonadidae fam. nov. is created to accommodate this species.

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