Vitellogenesis of the digenean Plagiorchis elegans (Rudolphi, 1802) (Plagiorchioidea, Plagiorchiidae) Samuel Greani a, ⁎, Yann Quilichini a , Joséphine Foata a , Stephen E. Greiman c , Papa Ibnou Ndiaye b , Vasyl V. Tkach c , Bernard Marchand a a University of Corsica, CNRS UMR 6134, Laboratory “Parasites and Mediterranean Ecosystems”, 20250 Corte, Corsica, France b Laboratory of Evolutionary Biology, Ecology and Management of Ecosystems, Faculty of Sciences and Techniques, Cheikh Anta Diop University of Dakar, BP 5055, Dakar, Senegal c Department of Biology, University of North Dakota, 10 Cornell Street, 101 Starcher Hall, Grand Forks, ND 58202, USA abstract article info Article history: Received 10 September 2013 Received in revised form 6 November 2013 Accepted 20 December 2013 Available online 22 February 2014 Keywords: Vitellogenesis Ultrastructure Plagiorchis elegans Plagiorchiidae Digenea The ultrastructural organization of vitellogenesis of Plagiorchis elegans (Rudolphi, 1802), experimentally obtained from the golden hamster Mesocricetus auratus (Linnaeus, 1758), is described using transmission electron microscopy. This study is the first ultrastructural study of vitellogenesis in a member of the superfamily Plagiorchioidea. The four stages usually observed during vitellogenesis are described: stage I, cytoplasm of the vitellocytes mainly filled with ribosomes and few mitochondria; stage II, beginning of the synthetic activity; stage III, active synthesis of the shell globule clusters; stage IV, vitellocytes are filled with shell globule clusters and contain several lipid droplets, and glycogen granules are grouped around clusters and droplets. Vitellogenesis in P. elegans is compared with that of other Digenea. The differences among P. elegans and previously studied digeneans include, but are not limited to the occurrence of dense coiled endoplasmic reticulum saccules and the concentration of glycogen in the mesenchyme, which may be considered as a fifth stage of maturation of the vitelline glands. This peculiarity was not observed in all trematodes, which clearly indicates differences in the vitellogenesis in various digenean lineages at different stages of maturation of their vitelline cells. © 2014 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Vitellogenesis of digenean trematodes has been the subject of light microscopical [1,2] and electron microscopical [3–6] studies. The Platyhelminthes are subdivided into two major groups corresponding to the organization of their female reproductive system: the Archoophora and the Neoophora. Digenea are part of the Neoophora, characterized by heterocellular female gonads composed of germaria (ovary) and vitellaria (vitelline gland) [7]. Each of these has a role in egg formation. Although vitellogenesis has been studied in members of several major digenean lineages, there is no published ultrastructural data on this pro- cess in members of the large superfamily Plagiorchioidae, which is the central taxon in the largest and most evolutionarily derived suborder Xiphidiata, order Plagiorchiida [8]. In this work, we present results of the ultrastructural study of vitellogenesis in Plagiorchis elegans, a widely distributed member of Plagiorchis, the type genus of the Plagiorchiidae (Lühe, 1901). Adult Plagiorchis are intestinal parasites of birds and mammals, occasionally of amphibians and reptiles [9]. More than 140 species have been formally described in the genus Plagiorchis (Lühe, 1899) mostly based on very few specimens. A majority of the descrip- tions paid rather little attention to the details of the female reproductive system [10]. The present work explores, for the first time, the ultrastructural organization of the female reproductive system in plagiorchiid digeneans. The aim of this study is to describe the ultrastructural organization of vitelline cells at different stages of vitellogenesis, and to compare our findings with the data known for other digenean species. 2. Materials and methods Adult specimens of P. elegans were obtained from the small intestine of an experimentally infected golden hamster Mesocricetus auratus. The life cycle of this digenean is propagated in the laboratory at the Depart- ment of Biology, University of North Dakota. Naturally infected snails Lymnaea stagnalis collected from a pond in Nelson County, eastern North Dakota, served as the original source of cercariae. Laboratory- bred juvenile snails L. stagnalis and larvae of mosquitoes Culex pipiens were subsequently used as the first and second intermediate hosts. The hamster was infected with larvae of C. pipiens harboring infective metacercariae. Live worms were removed from the intestine of M. auratus, quickly rinsed in saline and fixed in cold (4 °C) 2.5% glutar- aldehyde in 0.1 M sodium cacodylate buffer at pH 7.2, rinsed in 0.1 M Parasitology International 63 (2014) 537–543 ⁎ Corresponding author at: CNRS UMR SPE 6134 Université de Corse, Campus Grimaldi, BP 52, 20250 Corte, France. Tel.: +33 495 450 029; fax: +33 495 450 045. E-mail address: greani@univ-corse.fr (S. Greani). http://dx.doi.org/10.1016/j.parint.2013.12.010 1383-5769/© 2014 Elsevier Ireland Ltd. All rights reserved. Contents lists available at ScienceDirect Parasitology International journal homepage: www.elsevier.com/locate/parint