Étude de la faune microbienne et des paramètres physico-chimiques du tractus digestif d’annélides oligochètes, récoltés à Ebebda et à Nkolbikogo (région du Centre Cameroun)

The study focuses firstly on the morphological analysis of ciliates and secondly the variation in abundance of acaryotes and prokaryotes of the digestive tract of annelids Oligochaetes collected in the Center Region of Cameroon. In addition, the physicochemical parameters that influence the seriation of these microorganisms along the digestive tract of their hosts were analysed.The morphological study is based on the techniques of impregnation of specimens with the ammoniacal silver carbonate, the DAPI and the Feulgen nuclear staining. The surveys carried out on the annelid oligochaetes of the family of Glossoscolecidae have anabled the description of twenty species of ciliates belonging to Heterotrichs, Hysterocinetidae and Astomes. Amoung Heterotrichs, have been described three species of the genus Nyctotherus characterized by the presence of an apical secant system on their right side and a species of the genus Nyctotheroïdes characterized by the existence of three secant systems on their two sides: one on the right side and two on the left. Up to now, the presence of Heterotrichs was unsuspected in Glossoscolecidae. In Hysterocinetidae, the description of nine new species demonstrates the existence of four different types of skeletal pattern. The first type, present four superimposed and antagonistic skeletal fibre layers, corresponds to that of the genus Ptychostomum. The second type is characterized by the existence of an unorganized field of fibrillary structures forming a dense and undivided mass in the central part of the suction cup, for which a new genus is created: Ptychostomoïdes. The third type, present in the genus Proptychotomoïdes, is characterized by the existence of a glabrous surface in the central area of the adhesive apparatus. In the genus Thurstonia, an uncialiated kidney shape surface bordered subsequently by two mobile lips deprived of skeletal fibers was observed. This morphological diversity within Hysterocinetidae requires a new approach of the systematic in this group. In some Astomes (Almophrya bivacuolata and A. mediovacuolata), the analysis of the morphological variations of the nuclear apparatus allowed us to highlight important digitations and the presence of dark bands in the H macro-nucleus structure of the small cellular types, as well as the presence of intermediate forms between H and X macronucleus in these two species. In Almophrya laterovacuolata, the disposition of the vacuolar apparatus is variable: either two longitudinal lines are arranged among branches of the H macronucleus, or two longitudinal lines are out of the H macronucleus branches. These longitudinal lines may also be arranged without obvious order among the H macronucleus branches. Given that the identification within the genus Almophrya is specifically based on the number and the arrangement of vacuoles, a revision of these criteria is required. Four new species belonging to genera Anoplophrya, Hoplitophrya and Dicontophrya were also described in Astomes.In addition to the description of two new genera in Hysterocinetidae, four species in Heterotrichs, and seven species in Astomes, the technique of the cytometry in flow enabled us to highlight an unsuspected population of viruses in the digestive tract of the Glossoscolecidae as well as a population of bacteria not less important.The technique of aspiration under a vacuum pump allowed us to isolate and collect the intestinal liquid in three portions of the digestive tract of Alma emini. The correlations carried out between physico-chemical parameters and ciliates biomass held our attention. These results suggest that each portion of the digestive tract of Alma emini is a set of biotope niches, and microhabitats in which a large number of physical and chemical factors create ecological niches more suitable to a species or a group of species. This might explain the striation and the variation of abundance of the microfauna along the digestive tract of oligochaetes annelids.L’étude porte sur les analyses morphologiques des Protozoaires Ciliés et sur la variation d’abondance de virus et de bactéries du tube digestif d’annélides oligochètes de la famille des Glossoscolecidae récoltés dans la région du Centre Cameroun. De plus, les paramètres physico-chimiques susceptibles d’influencer la sériation de ces microorganismes le long du tube digestif de leurs hôtes ont été analysés. L’étude morphologique est basée sur les techniques d’imprégnation des spécimens au carbonate d’argent ammoniacal pyridiné et à la coloration au Di Aminido Phenyl Indol. Les prospections effectuées ont permis la description de vingt espèces de Ciliés appartenant aux Hétérotriches, Hysterocinetidés et Astomes. Chez les Hétérotriches dont la présence jusqu'ici était insoupçonnée chez les Glossoscolecidae, trois espèces du genre Nyctotherus ont été décrites ; caractérisées par la présence d’un système sécant apical sur leur face droite. Une espèce du genre Nyctotheroïdes a été décrite. Elle est caractérisée par l’existence de trois systèmes sécants dont un apical sur la face droite et deux (apical et caudal) sur la face gauche. Chez les Hysterocinetidés, la description de neuf espèces nouvelles démontre l’existence, au niveau de l’appareil adhésif de quatre types différents de topographies d’armature squelettique. Le premier, qui présente quatre strates de fibres squelettiques superposées et antagonistes, correspond à celui du genre Ptychostomum. Le second est caractérisé par l’existence d’un champ inorganisé de structures fibrillaires formant une masse dense et indivise dans la partie centrale de la ventouse, pour lequel un nouveau genre est créé : le genre Ptychostomoïdes. Le troisième type se distingue du précèdent par l’existence d’une aire glabre dans la région centrale de l’appareil adhésif. En fin le quatrième type, caractéristique du genre Thurstonia présente une aire non ciliée réniforme bordée postérieurement par deux lèvres mobiles et dépourvue de fibres squelettiques. Cette diversification morphologique au sein des Hysterocinetidés semble devoir imposer une nouvelle approche de la systématique de ce groupe. Les Ciliés Astomes Almophrya bivacuolata et A. mediovacuolata sont caractérisés par un macronoyau soit en X, en H, soit intermédiaire entre X et H. L’étude des variations morphologiques de l’appareil nucléaire chez ces espèces d’Almophrya révèle d’importantes digitations, des bandes sombres et d’interbandes dans la structure du macronoyau en H des petits types cellulaires. Chez A. laterovacuolata, la disposition de l’appareil vacuolaire est très variable : deux rangées longitudinales entre les branches du macronoyau en H; deux rangées longitudinales hors des branches de celui-ci ; sans ordre évident entre ses branches. Une révision des critères d’identification des Ciliés Almophrya semble devoir s’imposer. Quatre espèces nouvelles appartenant aux genres Anoplophrya, Hoplitophrya et Dicontophrya ont également été décrites chez les Astomes. Par ailleurs, la technique de la cytométrie en flux nous a permis de mettre en évidence une population jusqu’alors insoupçonnée de virus dans le tractus digestif des vers Glossoscolecidae ainsi qu’une population non moins importante de bactéries. La technique d’aspiration sous une pompe à vide a permis d’isoler et de recueillir le liquide intestinal du tube digestif de Alma emini. Les corrélations effectuées entre les paramètres physico-chimiques et les variations d’abondances des Ciliés ont été significatives. Ces résultats laissent supposer que chaque portion du tractus digestif de Alma emini est un ensemble de biotopes, de microhabitats dans lesquels un grand nombre de facteurs physiques et chimiques créent des niches écologiques plus favorables à une espèce ou à un groupe d’espèces. Ceci expliquerait la sériation et la variation d’abondance de la microfaune le long du tube digestif des annélides oligochètes

Description of five new species of hysterocinetian ciliates (Ciliophora, Hysterocinetidae), endocommensal in a terrestrial oligochaete of the genus Alma from Cameroon

International audienceStudies on five new species of hysterocinetian ciliates, endocommensal within a terrestrial oligochaete from the genus Alma (Cameroon), reveal the existence of three distinct types of cytoskeletal topography within their adhesive apparatus. In the first topographical type, four superimposed antagonistic strata of skeletal fibres that correspond to the arrangement observed in the genus Ptychostomum, Stein 1860 are found. The second topographical type is characterized by the existence of an unorganized field of fibrillar structures forming a single dense mass in the central part of the sucker. For this, a new genus is created: Ptychostomoides, Nana, Fokam, Ntoungwa et al. n. g. The third type present in the genus Proptychostomoides, Nana, Fokam, Ntoungwa et al. n. g. differs from the latter by the existence of a bare patch within the central region of the adhesive apparatus. This new evidence of morphological diversification within the Hysterocinetidae supports a new approach to the systematics of this group

Distribution of Astomatia Schewiakoff, 1896 and Hysterocinetidae Diesing, 1866 (Ciliophora, Oligohymenophora) along the digestive tract of Alma emini (Oligochaete, Glossoscolecidae) is correlated with physico-chemical parameters

International audienceThe paper demonstrates the influence of physico-chemical parameters on the distribution of endocommensal ciliates through the gut of the earthworm Alma emini. We measured physico-chemical parameters of the intestinal liquid extracted with the vacuum aspiration technique and concomitantly recorded biological parameter (species abundance). Furthermore, correlation analysis between physico-chemical parameters and biological parameter was performed in different compartments. In the foregut, among the eleven species of Astomatia recorded, correlation was significant between Metaracoelophrya intermedia, Coelophrya roquei and Water Content (WC = 46.94 ± 7.77%). In the midgut, among the nine species of Hysterocinetidae recorded, a significant correlation was observed between Metaptychostomum ebebdae, Ptychostomum macrostomum and Electric Conductivity (EC = 84.55 ± 12.94 μS/ cm). In the same compartment, a significant correlation was also observed between Ptychostomum macrostomum and Total Dissolved Substance (TDS = 16.20 ± 3.46%). In the hindgut, eight species of Astomatia were found, among which significant correlation was obtained between Coelophrya roquei and Hydrogen potential (pH = 7.35 ± 0.16). In the same compartment, taking into account the eleven species of Hysterocinetidae recorded, a significant correlation was also obtained between Ptychostomum macrostomum and pH; Ptychostomum commune and WC (28.84 ± 3.97%). These results suggest that each part of the digestive tract of A. emini can be considered as a set of natural microhabitats in which certain physico-chemical factors generate ecological niches suitable for one or another group of species

AGRO-MORPHOLOGICAL CHARACTERIZATION OF TWO RICE VARIETIES FROM JAPAN; ORYSA SATIVA L. AND FOUR NERICAS VARIETIES IN AN AGRO-ECOLOGICAL ZONE OF THE TOWN OF YAOUNDE (CAMEROON); COMPARATIVE STUDY OF THEIR PERFORMANCES

International audienceThe performances of two rice species of the genus Oryza were evaluated by considering parameters such as the number of panicle per rice plant, the number of primary branches of the panicles, panicle length, the plant height, the number of grains and empty balls per panicle. It appears that O. sativa from Japan has a number of empty balls less than NERICA’s varieties from Africa. We also noted that O. sativa has the highest number of panicles per rice plant (a mean of 14.05 ± 6.14). However, the number of grains per panicle NERICA’s varieties was very high (a mean of 164 ± 38.82) and therefore they shows more attractive characters than Orysa sativa lines. The differences were statistically significant above all the parameters considered in both African and Japan rice studied. A significant correlation that was negative has been observed between the number of panicles per rice plant and the number of primary branches per panicle within the NERICA 9 variety (P <0.05). The correlation was highly significant and positive (P <0.001) between the number of primary branches per panicle and the number of grain per panicle. These results suggest another demonstration of the hybrid vigor of NERICA varieties

Lacs Monoun et Nyos au Cameroun: quand la nature, la science et les pensées autochtones africaines se confrontent!

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Scientific culture and ancestral beliefs in sub-saharan Africa: The case of the murderous disasters of Lakes Monoun and Nyos in Cameroon

On August 15, 1984 at Lake Monoun and on August 21, 1986 at Lake Nyos, 37 and 1,746 people, respectively, died from gas fumes. Lakes Monoun and Nyos are peculiar aquatic ecosystems located on the Cameroon Volcanic Line, a strategic site, which continue to draw the attention of scientists, stakeholders, policy makers, public authorities as well as local communities and indigenous. It has been clearly demonstrated that these two lakes store large quantities of toxic gasses in dissolved form in their bottom. Indeed, the extremely diverse microbial communities that colonizes these lakes are capable of producing, storing and releasing gasses. These particularities have earned these lakes the name “killer lakes”. Although relevant results have been obtained after the installation of degassing devices on these lakes, these results are less popularized and Cameroonian society, in particular natives of the disaster-stricken areas have remained skeptic and divided on the origin of gasses: 9.4% of survivors and residents interviewed said it was a nuclear test. Also, 78.13% supported the thesis of a mystical-religious phenomenon. Only 12.47% of the interviewees understood that it was a scientifically explainable phenomenon. Clearly, the gap between science, scientists and societies is quite perceptible. Based on the deadly catastrophes of these two lakes, we present here the fracture that exists between science and African societies still anchored in indigenous beliefs

Taxonomical resolution and distribution of bacterioplankton along the vertical gradient reveals pronounced spatio-temporal patterns in contrasted temperate freshwater Lakes.

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[Revision of of the subfamily of Metaracoelophryinae de Puytorac 1972 (Oligohymenophora: Hoplytophryida: Hoplytophryidae), astome ciliates of the digestive tract of Oligochaeta worms of Africa: description of five new species].

International audienceFive new species belonging to the astome ciliates, living in the digestive tract of Oligochaeta worms belonging to the genus Alma from Cameroon, have been described. The techniques used are: vital staining, staining of the nucleus with Diamidino Phenyl Indol (DAPI), scanning electron microscopy and silver staining method (Fernandez Galiano, 1976, 1994). This work confirms the presence of the genus Paracoelophrya and Dicoelophrya in the digestive track of the oligochaete Alma from Gabon and Cameroon; it helps to understand the general taxonomy of this Metaracoelophryinae subfamily. Moreover, the homogeneity of this group is confirmed and the phylogenetic relationship inside the Hoplitophryida order need more studies to be solved

Impact of Rice Stem Borers and Identification of &lt;i&gt;Orseolia oryzivora&lt;/i&gt; Harris &amp; Gagn&#233;, 1982 (Diptera: Cecidomyiidae) Biotypes in the Southern Cameroon

International audienceThe study compares the impact due to rice stem borers in two sites (Yaoundé and Ntui). It also shows the diversity of the African Rice Gall Midge (AfRGM) biotypes in southern Cameroon (Santchou, Ndop, Tonga, Ebolowa, Baïgom, Yaoundé and Ntui). The New Rice for Africa (NERICA) varieties 3, 8, 9 and 13 sown in Ntui were less attacked than those sown in Yaoundé. At both sites, damages ranged from 0.78% to 2.7%. In terms of diversity, the main stem-borer species were O. oryzivora, Diopsis apicalis, D. longiconis and Chilo zacconius. Molecular analyses of Orseolia oryzivora larvae collected in the localities of Santchou, Ndop, Tonga, Ebolowa, Baïgom and Yaoundé showed the existence of more than one O. oryzivora biotype in southern Cameroon's rice basins

Morphological description of four new species of Nyctotherus (Ciliophora: Nyctotheridae: Heterotri- chida), commensal ciliates of the digestive tract of a terrestrial Oligochaete (Megascolecidae) from the northwest region of Cameroon

9International audienceThe morphology and ciliature of four Nyctotherus species (Nyctotherus orthostomatus n. sp., Nyctotherus ndoumeleleensis n. sp., Nyctotherus ngassami n. sp. and Nyctotherus atunibaensis n. sp.), isolated from the mid and hindgut of a Megascolecidae annelid of the genus Eupolytoreutus from the northwest region of Cameroon, were investigated using living observation (methylene blue) and silver impregnation methods (Fernandez-Galiano, 1994). Nyctotherus orthostomatus n. sp. is recognized by a pear-shaped body (128-152 × 95-104 µm); a conspicuous buccal apparatus with the peristome and the infundibulum perpendicular to each other; about 41-46 somatic kineties covering each side of the cell; one transversally elongated massive macronucleus located in the anterior third of the cell, surmounted by a very small spherical micronucleus. Nyctotherus ndoumeleleensis n. sp. is distinguished by the combination of the following characters: ovoid body (151-163 × 87-92 µm) with rounded poles; about 52-68 somatic kineties uniformly covering the cell body; an anterior, transversal and trapezoidal macronucleus carrying laterally a small micronucleus (2-3.5 µm in diameter). Nyctotherus ngassami n. sp. can be distinguished from its congeners by the following set of features: size about 153-269 × 102-148 µm; body ovoid, with 64-86 ciliary rows covering its surface; a small and globular micronucleus hidden by a transversal macronucleus located slightly above the equatorial part of the cell. Nyctotherus atunibaensis n. sp. is characterized by size about 145-253 × 95-162 µm, ovoid cell body, 108-122 somatic kineties,a transversal and arc-shaped macronucleus hiding a small micronucleus. In the present study, new locality (northwest region of Cameroon) and new species of the genus Nyctotherus are explored