Phylogenetic position and description of Rhytidocystis cyamus sp. n. (Apicomplexa, Rhytidocystidae): a novel intestinal
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ORIGINAL PAPER
Phylogenetic position and description of Rhytidocystis cyamus sp. n. (Apicomplexa, Rhytidocystidae): a novel intestinal parasite of the north-eastern Pacific ‘stink worm’ (Polychaeta, Opheliidae, Travisia pupa) Sonja Rueckert & Brian S. Leander
Received: 27 February 2009 / Revised: 14 May 2009 / Accepted: 20 May 2009 / Published online: 23 June 2009 # Senckenberg, Gesellschaft für Naturforschung and Springer 2009
Abstract A new Rhytidocystis species is described from the north-eastern Pacific Coast. Trophozoites of R. cyamus sp. n. were isolated from the intestines of the opheliid polychaete Travisia pupa, collected from mud dredged at a depth of 80 m. The trophozoites of R. cyamus sp. n. were relatively small (40–64 μm long, 27–30 μm wide) and bean-shaped with a centrally located nucleus. The trophozoite surface was inscribed by 10–12 longitudinal rows of short transverse folds and less conspicuous grooves with an irregular pattern. Micropores were observed in association with the transverse folds. A mucron or apical complex was not observed with either light or scanning electron microscopy. The trophozoites did not show any degree of motility. The SSU rDNA sequence obtained from R. cyamus sp. n. clustered strongly with R. polygordiae within the rhytidocystid clade. Although the precise phylogenetic position of the rhytidocystid clade within the Apicomplexa remains uncertain, the rhytidocystid sequences diverged with a weak affinity to a terrestrial clade containing cryptosporidians, neogregarines and monocystids. Keywords Alveolata . Apicomplexa . Agamococcidiorida . phylogeny . Rhytidocystis
S. Rueckert (*) : B. S. Leander Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Departments of Botany and Zoology, University of British Columbia, #3529 - 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada e-mail: [email protected]
Introduction Apicomplexans form a large and diverse group of unicellular parasites containing around 6,000 described species, and probably well over a million that still remain to be discovered (Adl et al. 2007; Hausmann et al. 2003). Despite the relatively well-studied intracellular pathogens of humans and livestock (e.g., Plasmodium—the causative agent of malaria—and Toxoplasma), the diversity of apicomplexans, especially those inhabiting the world’s oceans, has just started to be explored with molecular phylogenetic approaches. Among the least understood apicomplexans are gregarines and several coccidian-like lineages with uncertain phylogenetic positions (Leander and Ramey 2006; Kopečná et al. 2006). A growing knowledge of these lineages should elucidate the diversity and early evolutionary history of apicomplexans (Leander 2008). One of the poorly understood coccidian-like lineages are the so-called ‘Agamococcidiorida’ (Levine 1979), an illdefined group of apicomplexans with eucoccidian-like cyst characteristics (e.g., oocysts containing sporocysts with two sporozoites each), but supposedly lacking gamonts and merogony (Cox
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