Ultrastructure of the Spermatozoon of the Digenean Plagiorchis elegans (Rudolphi, 1802) (Plagiorchioidea, Plagiorchiidae) Papa Ibnou Ndiaye, 1 Yann Quilichini, 2 * Vasyl V. Tkach, 3 Stephen E. Greiman, 3 Cheikh Tidiane B ^ a, 1 and Bernard Marchand 2 1 Laboratory of Evolutionary Biology, Ecology and Management of Ecosystems, Faculty of Sciences and Techniques, Cheikh Anta Diop University of Dakar, BP 5055, Dakar, Republic of Senegal 2 CNRS UMR 6134, University of Corsica, Laboratory “Parasites and Mediterranean Ecosystems”, 20250 Corte, Corsica, France 3 Department of Biology, University of North Dakota, Grand Forks, North Dakota, USA ABSTRACT The ultrastructure of the mature sperma- tozoon of the type genus of the Plagiorchiidae Pla- giorchis elegans (Rudolphi, 1802), a parasite of the Golden hamster, Mesocricetus auratus is described. This study is the first ultrastructural study of the sper- matozoon of a Plagiorchis, the second of a plagiorchiid species and only the third in the Plagiorchioidea. Previ- ously data on spermatozoon ultrastructure existed only for the plagiorchiid Enodiotrema reductum and the omphalometrid Rubenstrema exasperatum. The mature spermatozoon of P. elegans exhibited the general pat- tern described in most digenean species, namely two axonemes of the 9 1 “1” Trepaxonemata pattern, nu- cleus, mitochondria, external ornamentation of the plasma membrane, spine-like bodies, and glycogen granules. However, the rather typical expansion of the plasma membrane is not found in P. elegans. Another peculiarity of the spermatozoon of P. elegans is the presence of a structure called thin cytoplasm termina- tion. Spermatozoon ultrastructure of P. elegans is com- pared with that of E. reductum and R. exasperatum. Spermatozoon of P. elegans conforms to the general pat- tern described in E. reductum. Thus, this study further expands our knowledge on the spermatozoon ultrastruc- ture among the members of the Plagiorchioidea, one of the most phylogenetically derived groups of the digenea. J. Morphol. 274:965-972, 2013. V C 2013 Wiley Periodicals, Inc. KEY WORDS: Plagiorchis elegans; Plagiorchiidae; Dige- nea; spermatozoon; electron microscopy INTRODUCTION Plagiorchis elegans (Rudolphi, 1802) is a species of plagiorchiid digeneans widely distributed in Europe and parts of North America. It is character- ized by an unusually broad definitive host range, occurring in birds, mammals, and even some reptil- ian sauropsids (Sharpilo and Iskova, 1989). It belongs to the type genus Plagiorchiidae L€ uhe, 1901 which is the central family of the superfamily Pla- giorchioidea L€ uhe, 1901. The family Plagiorchiidae has arguably the most complex taxonomic history of all digeneans. At present, there are still numerous questions and controversies regarding the structure of the Plagiorchiidae and evolutionary interrelation- ships among its members (Tkach, 2008). Some of these questions concern its type-genus Plagiorchis L€ uhe, 1899 (Tkach et al., 2000b; Tkach, 2008). A significant progress in our understanding of the Plagiorchioidea phylogeny and improvements of the system of this superfamily have been recently made using molecular tools (Tkach et al., 2000a,b,2001; Olson et al., 2003). However, data from another independent and potentially very use- ful source of characters for phylogenetic inference, namely the ultrastructure of spermatozoa, are almost completely lacking for the Plagiorchioidea. The importance of ultrastructural studies of the spermatozoon for phylogenetic purposes in the Pla- tyhelminthes has been clearly demonstrated in numerous studies (Justine, 1991a,b,1995, 1998; Levron et al., 2010). Among the 23 currently recog- nized families of the Plagiorchioidea, information on the spermatozoon ultrastructure exists only for members of two families, an omphalometrid Ruben- strema exasperatum (Rudolphi, 1819) an intestinal parasite of shrews (Bakhoum et al., 2011) and a pla- giorchiid Enodiotrema reductum Looss, 1901 a stomach parasite of Green sea turtle Chelonia mydas (Ndiaye et al., 2012a). This work describes the ultrastructure of the mature spermatozoon of Contract grant sponsor: National Institutes of Health, USA; Con- tract grant number: R15AI092622. *Correspondence to: Yann Quilichini, CNRS UMR SPE 6134, Uni- versity of Corsica, Campus Grimaldi, BP 52, 20250 Corte, France. E-mail: quilichini@univ-corse.fr Received 12 February 2013; Revised 28 February 2013; Accepted 9 March 2013. Published online 30 April 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/jmor.20152 V C 2013 WILEY PERIODICALS, INC. JOURNAL OF MORPHOLOGY 274:965–972 (2013)