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      Ultrastructural study of vitellogenesis and oogenesis of Crepidostomum metoecus (Digenea, Allocreadiidae), intestinal parasite of Salmo trutta (Pisces, Teleostei)

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          Abstract

          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.

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          Most cited references 28

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

           P D Erasmus (1973)
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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.
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                Author and article information

                Journal
                Parasite
                Parasite
                EDP Sciences
                1776-1042
                2016
                November 2016
                : 23
                :
                : 47
                Article
                10.1051/parasite/2016057
                © 2016

                This work is licensed under a Creative Commons Attribution 4.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

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                Self URI (journal page): http://www.parasite-journal.org/

                Parasitology, Life sciences

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