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      Ultrastructural study of vitellogenesis and oogenesis of Crepidostomum metoecus (Digenea, Allocreadiidae), intestinal parasite of Salmo trutta (Pisces, Teleostei) Translated title: Étude ultrastructurale de la vitellogénèse et de l’ovogénèse de Crepidostomum metoecus (Digenea, Allocreadiidae), parasite intestinal de Salmo trutta (Pisces, Teleostei)

      1 , * , 1 , 1


      EDP Sciences

      Oogenesis, Vitellogenesis, Crepidostomum, Digenea

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          We describe the vitellogenesis and oogenesis of Crepidostomum metoecus from Salmo trutta collected in Corsica. This is the first study conducted in the Allocreadiidae family. The maturation of C. metoecus vitellocytes comprises four different stages depending on organelle content. The follicular vitellarium is surrounded by a basal lamina. Vitellocytes are randomly distributed into the vitellarium, although fully mature vitellocytes are found in the center of the follicle. During maturation, the nucleo-cytoplasmic ratio decreases, whereas synthetic activity increases. Fully mature vitellocytes are filled with β-glycogen particles and shell globule clusters. Compared to other trematodes studied, C. metoecus possesses a large amount of nutritive reserves for the developing embryo and high quantities of material for the developing shell. Oocyte maturation takes place in four stages: oogonia, primary oocytes, developing oocytes, and mature oocytes. Developing oocytes enter the zygotene-pachytene stage of the first meiotic division recognizable by the presence of synaptonemal complexes in the nucleoplasm. The low protein composition of mature oocytes associated with the large nutrient content of vitellocytes of C. metoecus enables us to consider that oocytes do not take part of the nutrition of the future embryo of the miracidium. A cytochemical test (Thiéry method) allowed us to detect the presence of polysaccharides and glycogen during maturation of these two cell types.

          Translated abstract

          Nous décrivons la vitellogenèse de Crepidostomum metoecus (de Salmo trutta récolté en Corse). Cette étude est la première menée dans la famille Allocreadiidae. La maturation des vitellocytes de C. metoecus comprend quatre stades différents, en fonction des organites qu’ils contiennent. Le vitellarium folliculaire est entouré par une lame basale. Les vitellocytes sont distribués au hasard dans le vitellarium, cependant les vitellocytes pleinement mûrs se trouvent dans le centre du follicule. Au cours de la maturation le rapport nucléo-cytoplasmique diminue, tandis que l’activité de synthèse augmente. Les vitellocytes mûrs contiennent des particules de β-glycogène et des grappes de globules pour la formation de la coquille. Par rapport à d’autres trématodes étudiés, C. metoecus possède une grande quantité de réserves nutritives pour le développement de l’embryon, et beaucoup de matériel pour le développement de la coquille. La maturation des ovocytes se déroule en quatre étapes: ovogonies, ovocytes primaires, ovocytes en développement, et ovocytes mûrs. Les ovocytes en développement entrent dans la phase zygotène-pachytène de la première division méiotique, reconnaissable par la présence de complexes synaptonémaux dans le nucléoplasme. La faible composition en protéines des ovocytes mûrs associée à la grande teneur en éléments nutritifs des vitellocytes de C. metoecus, nous permettent de considérer que les ovocytes ne participent pas à la nutrition du futur embryon du miracidium. Un test cytochimique (méthode de Thiéry) nous a permis de localiser la présence de polysaccharides et de glycogène pendant ces deux maturations cellulaires.

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          A comparative study of the reproductive system of mature, immature and "unisexual" female Schistosoma mansoni.

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            A new description of the reproductive system of Schistosoma mansoni (Trematoda: Schistosomatidae) analyzed by confocal laser scanning microscopy.

            Classical schemes of the adult Schistosoma mansoni reproductive system have been described. In our study, whole adult worms derived from unisexual or mixed infections and stained with carmine chlorine were virtually and tomographically analyzed under confocal laser scanning microscopy. We found that: (1) there were morphological differences in the ovary, vitteline glands and testicular lobes between specimens derived from unisexual or mixed infections; (2) there was always a single lobed ovary (three or four lobes), presenting differentiation from the anterior to the posterior lobes, where the most mature oocytes were located; (3) the proximal segment of oviduct was connected to an ampullary dilatation, full of tailed spermatozoa, characterizing a seminal receptacle; (4) there was no long vitelline duct, but a short one that begins at the end of the proximal region of the vitelline gland; (5) long cells of Mehlis' gland placed radially around the ootype were not observed. Otherwise, the ootype was only lined by thick cuboidal epithelial cells with plaited bases and nuclei with flabby chromatin, making a clear distinction from the uterine epithelium. This morphological feature suggests that each cell represents a gland. (6) In coupled males, the specimens located inside the gynaecophoric canal had smaller testicular lobes, suckers, and body length and width when compared to their partners. Our results show that the reproductive system does not follow a unique pattern within flatworms. Due to its better resolution, confocal laser scanning microscopy, using a reflected mode with tomographic sections, allows new interpretations, modifying the adopted and current descriptions of the internal morphological structures of S. mansoni adult worms.
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              A comparative study of the vitelline cell in Schistosoma mansoni, S. haematobium, S. japonicum and S. mattheei.

              A comparison is given of the ultrastructure of the vitelline cell in Schistosoma mansoni, S. haematobium, S. japonicum and S. mattheei. Four stages in development of the vitelline cell have been categorized as follows: Stage 1, the undifferentiated cell; Stage 2, the developing cell showing the beginning of synthetic activity; Stage 3, the developing cell showing active protein synthesis; Stage 4, the fully mature vitelline cell. These stages in development have been defined morphologically and Stages 1, 2 and 3 are very similar in all 4 species. Lipid is present in the Stage 4 cells of all species but appears earlier at Stage 3 in S. haematobium and S. mattheei. There are several differences as to the intercellular inclusions of the Stage 4 cells, the most marked of these being the absence of calcareous corpuscles from S. japonicum as compared with the other 3 species.

                Author and article information

                EDP Sciences
                15 November 2016
                : 23
                : ( publisher-idID: parasite/2016/01 )
                [1 ] University of Corsica, CNRS, UMR 6134 – SPE, Parasites and Mediterranean Ecosystems Laboratory 20250 Corte Corsica France
                Author notes
                [* ]Corresponding author: greani@ 123456universita.corsica
                parasite160001 10.1051/parasite/2016057
                © S. Greani et al., published by EDP Sciences, 2016

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Page count
                Figures: 6, Tables: 1, Equations: 0, References: 53, Pages: 10
                Research Article

                oogenesis, vitellogenesis, crepidostomum, digenea


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