European Journal of PROTISTOLOGY European Journal of Protistology 44 (2008) 168–180 The bacterivorous ciliate Cyclidium glaucoma isolated from a sewage treatment plant: Molecular and cytological descriptions for barcoding Matteo Guggiari, Robert Peck à Department of Zoology and Animal Biology, University of Geneva, Sciences III, 30 Quai Ernest Ansermet, 1211 Geneva 4, Switzerland Received 2 August 2007; received in revised form 14 November 2007; accepted 15 November 2007 Abstract A strain of Cyclidium isolated from a sewage treatment plant in Geneva, Switzerland, was cloned and cultured under laboratory conditions before being characterized cytologically and molecularly. Information about the classical morphology and also about new molecular sequences has been obtained permitting its identification as Cyclidium glaucoma. The molecular description includes the 18S rRNA sequence, and for the first time for C. glaucoma the ITS-1, 5.8S, ITS-2 sequence, and the mitochondrial Cytochrome oxidase C subunit 1 sequence. Three divergence groups were identified for C. glaucoma using a short rDNA sequence for evolutionary distance analysis. These groups correspond to the three ribotype lineages previously described for C. glaucoma. We discuss the possibility that C. glaucoma is a species complex containing three cryptic species, the problems of species definition in the protozoa and the choice of a barcoding molecule for the ciliates. r 2007 Elsevier GmbH. All rights reserved. Keywords: Cyclidium glaucoma; Ciliate; Identification; Barcode; Sewage; Species concept Introduction Cyclidium glaucoma (O.F. Mu¨ller, 1773) has been described on numerous occasions at increasing levels of microscopic resolution (e.g. Bardele 1983; Berger and Thompson 1960; Parducz 1940). Although several papers dealing with different Cyclidium spp. have been published (Berger 1959; Borror 1965; Clarke et al. 1993; Esteban et al. 2000; Foissner et al. 1994; Grolie` re 1980; Song 2000; Wilbert 1986), C. glaucoma remains the most studied and the best characterized (Bick 1972; Corliss 1979; Foissner et al. 1994; Lynn and Small 2002; Patterson and Hedley 1992). Misidentification of Cyclidium species is a potential problem (Fenchel and Finlay 2006; Foissner et al. 1994; Song 2000) especially because species have been characterized morphologically using staining tech- niques of variable quality, or specimens are from a range of geographic locations and may present a ‘‘continuum of morphotypes’’ (Finlay et al. 1996). Thus, DNA sequences may provide necessary, supplementary information for Cyclidium spp. identifications. To date sequences of rDNA of four Cyclidium species (C. glaucoma, C. porcatum, C. plouneouri, and C. citrullus) have been reported (Embley et al. 1995; Finlay et al. 2006) and are currently available in the databases. Most of them (109/116) concern C. glaucoma. Our analysis concerns a strain of C. glaucoma, referred to as C. glaucoma Ge-Vil, that was isolated from a sewage treatment plant in Geneva, Switzerland, ARTICLE IN PRESS www.elsevier.de/ejop 0932-4739/$ - see front matter r 2007 Elsevier GmbH. All rights reserved. doi:10.1016/j.ejop.2007.11.004 à Corresponding author. E-mail address: robert.peck@zoo.unige.ch (R. Peck).