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Etude morphologique et phylogénie des Ciliés Astomes endocommensaux d'Oligochètes terricoles de la région de Yaoundé et ses environs

Abstract : The study deals with the systematic of the microbial endofauna of terricolous Oligochaeta Megascolecidae and Glossoscolecidae of the area of Yaounde, with a particular emphasis on the morphological and genetic analysis of Astomatous ciliates present in their digestive tract. A systematic revision of the family of Radiophryidae de Puytorac 1972 is carried out, with the description of five new species of the subfamily of Metaracoelophryinae de Puytorac, 1972. It makes it possible on the one hand, to confirm the presence of the genera Paracoelophrya and Dicoelophrya in the digestive tract of Oligochaeta earthworms of the genus Alma of Gabon and Cameroun and to confirm the homogeneity of this group on the other hand. The question of the phylogenetic relationship of Hoplitophryida is raised once more. The diversity of organisation of the nuclear apparatus in the genus Almophrya is studied through observations on the morphological variations of the nuclear apparatus after staining of the specimens with Diamidino Phényl Indol (Johnson et al., 1982), Feulgen or the ammoniacal silver carbonate (Fernandez Galiano, 1994). A new species is described: Almophrya nkoldensis n. sp. Futher more, the process of the morphogenesis of bipartition in three species of Astomes was studied; showing various alternatives of this division, besides traditional binary fission (Eudrilophrya complanata), the radiate and distal palintomie in Buchneriella eupolytoreuti n.sp.was specified. In addition, the process of the conjugation was explored in Eudrilophrya simplex n.sp. The analysis of the RNA gene sequences of small sub unit of ribosomal RNA (SSrRNA) in Anoplophrya marylandensis places this species of Astomatous Ciliate in the Class Oligohymenophorea (Affa'a et al., 2004). However, the gene sequence of only one species is insufficient to establish with confidence the phylogenetic relations in a large group. Consequently, we obtained sequences SSrRNA the gene of nine additional species distributed in six genera and the three orders of the subclass Astomatia: Hoplitophryida Cheissin, 1930 em., de Puytorac, 1972 ; Anoplophryida Cépède, 1910 et Haptophryida Cépède, 1923 (1910). A new genus of clausilocolidae de Puytorac in Corliss, 1979 is proposed: Paraclausilocola nov. gen., with two new species: P. constricta n. sp and P. elongata n. sp. This new genus is representative of the order Haptophryidae. The phylogenetic tree obtained shows a strong affinity of the sequences of new Astomatous Ciliates studied with that of A. marylandensis. The branch is precise and shows a considerable genetic distance with the other subclasses of Oligohymenophorea. This tree reveals Astomes like a sister clade of Scuticociliates, confirming the hypothesis that Astomes form a monophyletic group belonging to the class of Oligohymenophorea de Puytorac, 1954; Affa‟a et al., 2004). In the subclass of Astomatia, we find two branches quite distinct: one with the genera Anoplophrya, Almophrya and Metaracoelophrya; the second with the remaining genera: Eudrilophrya, Metaradiophrya, Paraclausilocola, and Njinella. Taking into consideration this grouping, ordinal attributions and assignments of the genus to the families in the two current classifications: that of de Puytorac (1994) and Lynn (2008) do not seem supported any more.
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Zéphyrin Fokam. Etude morphologique et phylogénie des Ciliés Astomes endocommensaux d'Oligochètes terricoles de la région de Yaoundé et ses environs. Sciences du Vivant [q-bio]. Université de Yaoundé I, 2012. Français. ⟨NNT : ⟩. ⟨tel-00918304⟩

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