Publications Articles

Mise à jour le : 25/07/2019

par la rédaction 12h00 mn

  1. Loubelo Madiela Bill Donatien, Arvor D3, Durieux L., Bouka Biona Clobite et Durieux L., 2015-2017. Classification des séries temporelles landsat- 8 pour la cartographie du Gradient de végétation dans le nord de la République du Congo. Annales de l’Université Marien Ngouabi. 2015-2017 ; 16(1) : 1p. 1-21.

 

  •  : Cette étude a permis d’élaborer une carte détaillée du gradient de la végétation dans le bassin du Congo sous une résolution de 30 m. elle caractérise la couverture terrestre à partir d’une discrimination spatiale améliorée. Une approche automatique de classification de différentes thématiques d’occupation des sols, basée sur les règles de classification proposées par Baraldi et al. (2006), a linéaire (LMM), nous avons traité 28 images Landsat-8 d’une série temporelle dans un site du département de la sangha dans le nord de la République du Congo. Nous avons ainsi estimé la proportion de pixels des classes végétations, minéral eau/ombres, afin de produire une image annuelle presque sans nuage. La classification obtenue a permis de générer une carte de végétation de huit classes sémantiques allant de la classe « forêt marécageuse » à la classe « eau ». La validation de la qualité de la classification à partir d’une fusion des classes ayant des proches appartenances de pixels, a généré des indices de validation satisfaisants dont 0,89 pour l’indice global de précision et 0,85 pour l’indice kappa, les seuils standards de satisfaction admis dans la littérature étant supérieurs ou égaux respectivement à 0,85 et 0,75. Cependant, des pixels mal classés dans la maitrise de confusion apparaissent principalement entre les classes « forêt marécageuse » et « forêt dense ». Cette approche de fusion des classes sémantiques d’occupation des sols tout en conservant les informations textures de l’image brute.

 

  •  : végétation ; image Landsat ; modèle de démixage linéaire ; séries temporelles ; classes sémantiques ; République du Congo.

 

  1. Christiane Paul, Frank Kirschbaum,Victor Mamonékéné & Ralph Tiedemann, 2016. Evidence for Non-neutral Evolution in a Sodium Channel Gene in African Weakly Electric Fish (Campylomormyrus, Mormyridae). Journal of Molecular Evolution. 82(6) 245-314.

 

  • : Voltage-gated sodium channels, Nav1, play a crucial role in the generation and propagation of action potentials and substantially contribute to the shape of their rising phase. The electric organ discharge (EOD) of African weakly electric fish (Mormyroidea) is the sum of action potentials fired from all electrocytes of the electric organ at the same time and hence voltage-gated sodium channels are one factor—together with the electrocyte’s morphology and innervation pattern—that determines the properties of these EODs. Due to the fish-specific genome duplication, teleost fish possess eight copies of sodium channel genes (SCN), which encode for Nav1 channels. In mormyroids, SCN4aa is solely expressed in the electrocytes of the adult electric organ. In this study, we compared entire SCN4aa sequences of six species of the genus Campylomormyrus and identified nonsynonymous substitutions among them. SCN4aa in Campylomormyrus exhibits a much higher evolutionary rate compared to its paralog SCN4ab, whose expression is not restricted to the electric organ. We also found evidence for strong positive selection on the SCN4aagene within Mormyridae and along the lineage ancestral to the Mormyridae. We have identified sites at which all nonelectric teleosts are monomorphic in their amino acid, but mormyrids have different amino acids. Our findings confirm the crucial role of SCN4aa in EOD evolution among mormyrid weakly electric fish. The inferred positive selection within Mormyridae makes this gene a prime candidate for further investigation of the divergent evolution of pulse-type EODs among closely related species.

 

  • :  Mormyridae, Mormyroidea, Campylomormyrus, SCN4aa, Voltage-gated sodium channel, Positive selection.

 

  1. Armel Ibala Zamba, Victor Mamonekene, Emmanuel Vreven and Melanie L. J. Stiassny, 2016. Rehabilitation of Xenocharax crassus (Teleostei: Distichodontidae), a species endemic to the Congo basin in central Africa. An international journal for field-orientated ichthyology. Volume 27 • Number 4 • December 2016 pages 289-384, 49 figs., 14 tabs.

 

  • : Xenocharax crassus Pellegrin, 1900, originally described from the Alima River (Congo basin, Republic of Congo) but synonymised with X. spilurus by Daget in 1960, is rehabilitated. Xenocharax crassus, a Congo basin endemic, is distinguished from X. spilurus, the latter found exclusively in basins of the Lower Guinean ichthyofaunal province, by the presence of a large black mark on the anterior part of the dorsal fin (versus absence), a small, round, black spot at the base of the caudal peduncle (versus a large ovoid spot covering the peduncle base), and a wider mouth (29-34 % HL vs. 24-29). For specimens of similar sizes, X. crassus has a shorter dorsal-adipose distance than X. spilurus. Furthermore, most X. crassus specimens have 6 supraneurals (frequency: 83 %) versus 7 (frequency: 79 %) in X. spilurus. With molecular data the species is readily distinguished from X. spilurus by 10 apomorphic, non-synonymous nucleotide transitions in the three sampled genetic markers (nd2, cyt-b, and myh6). A lectotype is designated for X. spilurus.

 

  1. Robert G. M. Spencer, Peter J. Hernes, Bienvenu Dinga, Jose N. Wabakanghanzi, Travis W. Drake1, and Johan Six, 2016. Origins, seasonality, and fluxes of organic matter in the Congo River. Global Biogeochemical Cycles. P. 1105- 1121.

 

  • : The Congo River in central Africa represents a major source of organic matter (OM) to the Atlantic Ocean. This study examined elemental (%OC, %N, and C:N), stable isotopic (δ13C and δ15N), and biomarker composition (lignin phenols) of particulate OM (POM) and dissolved OM (DOM) across the seasonal hydrograph. Even though the Congo exhibits an extremely stable intra-annual discharge regime, seasonal variability in OM composition was evident. DOM appears predominantly derived from vascular plant inputs with greater relative contribution during the rising limb and peak in discharge associated with the major November–December discharge maximum. Generally, POM appears to be sourced from soil-derived mineral-associated OM (low C:N, low Λ8, and higher (Ad:Al)v) but the relative proportion of fresh vascular plant material (higher C:N, higher Λ8, and lower (Ad:Al)v) increases with higher discharge. During the study period (September 2009 to November 2010) the Congo exported 29.21 Tg yr_1 of total suspended sediment (TSS), 1.96 Tg yr_1 of particulate organic carbon (POC), and 12.48 Tg yr_1 of dissolved organic carbon. The Congo exports an order of magnitude lower TSS load in comparison to other major riverine sources of TSS (e.g., Ganges and Brahmaputra), but due to its OM-rich character it actually exports a comparable amount of POC. The Congo is also 2.5 times more efficient at exporting dissolved lignin per unit volume compared to the Amazon. Including Congo dissolved lignin data in residence time calculations for lignin in the Atlantic Ocean results in an approximately 10% reduction from the existing estimate, suggesting that this material is more reactive than previously thought.

 

  1. Jordon D. Hemingway, Enno Schefuß, Bienvenu Jean Dinga, Helena Pryer, Valier V. Galy, 2016. Multiple plant-wax compounds record differential sources and ecosystem structure in large river catchments. Geochimica et Cosmochimica Acta 184 (2016) 20–40.

 

  • :  The concentrations, distributions, and stable carbon isotopes (d13C) of plant waxes carried by fluvial suspended sediments contain valuable information about terrestrial ecosystem characteristics. To properly interpret past changes recorded in sedimentary archives it is crucial to understand the sources and variability of exported plant waxes in modern systems on seasonal to inter-annual timescales. To determine such variability, we present concentrations and d13C compositions of three compound classes (n-alkanes, n-alcohols, n-alkanoic acids) in a 34-month time series of suspended sediments from the outflow of the Congo River. We show that exported plant-dominated n-alkanes (C25–C35) represent a mixture of C3 and C4 end members, each with distinct molecular distributions, as evidenced by an 8.1 ± 0.7‰ (±1r standard deviation) spread in d13C values across chain-lengths, and weak correlations between individual homologue concentrations (r = 0.52–0.94). In contrast, plantdominated n-alcohols (C26–C36) and n-alkanoic acids (C26–C36) exhibit stronger positive correlations (r = 0.70–0.99) between homologue concentrations and depleted d13C values (individual homologues average 6!31.3‰ and !30.8‰, respectively), with lower d13C variability across chain-lengths (2.6 ± 0.6‰ and 2.0 ± 1.1‰, respectively). All individual plant-wax lipids show little temporal d13C variability throughout the time-series (1r 6 0.9‰), indicating that their stable carbon isotopes are not a sensitive tracer for temporal changes in plant-wax source in the Congo basin on seasonal to inter-annual timescales. Carbon-normalized concentrations and relative abundances of n-alcohols (19–58% of total plant-wax lipids) and n-alkanoic acids (26–76%) respond rapidly to seasonal changes in runoff, indicating that they are mostly derived from a recently entrained local source. In contrast, a lack of correlation with discharge and low, stable relative abundances (5–16%) indicate that n-alkanes better represent a catchment-integrated signal with minimal response to discharge seasonality. Comparison to published data on other large watersheds indicates that this phenomenon is not limited to the Congo River, and that analysis of multiple plant-wax lipid classes and chain lengths can be used to better resolve local vs. distal ecosystem structure in river catchments.

 

  • : Plant waxes; Biomarkers; Riverine sediments; Carbon isotopes; Paleo proxies.

 

  1. Avor Damien, Loubelo Madiela Bill Donatien, Corpetti Thomas, 2016. Semantic pre-classification of vegetation grandient based on linearly unmixed landsat time series. 2016 IEEE International Geosciences and Remote Sensing Symposium (IGARSS). https://ieeexplore.ieee.org/document/7730152. p. 1-4.

 

  • : Mapping vegetation in the tropics is of primary importance to assess its contribution to important ecosystem services. This implies to implement methods to capture the vegetation gradient that characterizes land cover in these regions. Linear Mixture Models have long been used to monitor this gradient. In the present study, we automatically unmixed six Landsat-8 images of a study area in the Republic of Congo. We then computed the weighted average fraction of mineral, vegetation and water/shadow classes for each pixel in order to produce an annual (nearly) cloud-free unmixed image. Finally this product is pre-classified into six semantic classes ranging from “very dark” to “very bright” classes to discriminate the vegetation gradient based on its visual appearance. Results indicate the ability of the approach to classify fine land cover classes while still keeping textural information of the raw image.

Mots clés: Vegetation, Landsat, Linear Mixture Model, time series, semantic classes

 

  1. Francesco Lamanna, Frank Kirschbaum, Anja R.R. Ernst, Philine G.D. Feulner, Victor Mamonekene, Christiane Paul, Ralph Tiedemann, 2016. Species delimitation and phylogenetic relationships in a genus of African weakly-electric fishes (Osteoglossiformes, Mormyridae, Campylomormyrus) Molecular Phylogenetics and Evolution 8-18.

 

  • :  African weakly electric mormyrid fish show a high diversity of their electric organ discharge (EOD) both across and within genera. Thanks to a recently developed technique of artificial reproduction in mormyrid fish, we were able to perform hybridizations between different genera and within one genus (Campylomormyrus). The hybrids of intergenus hybridizations exhibited different degrees of reduced survival related to the phylogenetic distance of the parent species: hybrids of the crosses between C. rhynchophorus and its sister genus Gnathonemus survived and developed normally. Hybrids between C. rhynchophorus and a Mormyrus species (a more basal clade compared to Campylomormyrus s) survived up to 42 days and developed many malformations, e.g., at the level of the unpaired fins. Hybrids between C. numenius and Hippopotamyrus pictus (a derived clade, only distantly related to Campylomormyrus) only survived for two days during embryological development. Eight different hybrid combinations among five Campylomormyrus species (C. tamandua, C. compressirostris, C. tshokwe, C. rhynchophorus, C. numenius) were performed. The aim of the hybridizations was to combine species with (1) either caudal or rostral position of the main stalk innervating the electrocytes in the electric organ and (2) short, median or long duration of their EOD. The hybrids, though they are still juveniles, show very interesting features concerning electrocyte geometry as well as EOD form and duration: the caudal position of the stalk is prevailing over the rostral position, and the penetration of the stalk is dominant over the non-penetrating feature (in the Campylomormyrus hybrids); in the hybrid between C. rhynchophorus and Gnathonemus petersii it is the opposite. When crossing species with long and short EODs, it is always the long duration EOD that is expressed in the hybrids. The F1-Hybrids of the cross C. tamandua _ C. compressirostris are fertile: viable F2-fish could be obtained with artificial reproduction.

 

  1. Linh Nguyen, Christiane Paul, Victor Mamonékéné, Peter Bartsch, Ralph Tiedemann et Frank Kirschbaum, 2017. Reproduction and development in some species of the weakly electric genus Campylomormyrus (Mormyridae,Teleostei). Environ Biol Fish (2017) 100:49–68.

 

  • :  Reproduction in captivity of four species of the mormyrid genus Campylomormyrus was investigated. Cyclical reproduction was provoked by changing water conductivity (C) alone: decreasing C led to gonadal recrudescence, an increase induced gonad regression. Data on the reproduction and development of three species are presented. All three species are indeterminate fractional spawners. Spawning intervals ranged from 6 to 66 days in C. rhynchophorus, 10–75 days in C. tshokwe, and 18 days in C. compressirostris (calculated values). Fecundities (eggs per fractional spawning) ranged from 70 to 1570 eggs in C. rhynchophorus, 100–1192 in C. tshokwe, and 38–246 in C. compressirostris. Spawnings/ovipositions occurred during the second half of the night; no parental care was observed; no special spawning substrates were necessary. C. compressirostris successfully spawned in breeding groups, C. rhynchophorus as pair. Agonistic behavior in the C. tshokwe pair forced us to divide the breeding tank; therefore, only ovipositions occurred. However, injection of an artificial GnRH hormone allowed us to obtain ripe eggs and sperm and to perform successful artificial reproduction. All three species produce yolky, slightly sticky eggs. Egg diameter ranges from 2.3–3.0 mm. Hatching occurred on day 3, feeding started on day 11. Transition from larval to juvenile stage occurred at around 20 mm total length (TL). At this size C. rhynchophorus developed a higher body than the two other species and differences between the species in the melanin pigmentation of the unpaired fins occurred. Between 32 and 35 mm TL the upper and lower jaws started to elongate.

Mots clés:Keywords Campylomormyrus . Cyclical reproduction. Environmental factors. Behavior. Ontogeny. Artificial.

 

  1. Frank Kirschbaum, Linh Nguyen, Stephanie Baumgartner, Hiu WanLinda Chi, Rene Wolfart, Khouloud Elarbani, Hari Eppenstein, Yevheniia Korniienko, Lilian Guido-Bohm, Victor Mamonekene, Marianne Vater, Ralph Tiedemann, 2017. Intragenus (Campylomormyrus) and intergenus hybrids in mormyrid fish: Physiological and histological investigations of the electric organ ontogeny. Journal of Physiology – Paris p. 1-21.

 

  • :  African weakly electric mormyrid fish show a high diversity of their electric organ discharge (EOD) both across and within genera. Thanks to a recently developed technique of artificial reproduction in mormyrid fish, we were able to perform hybridizations between different genera and within one genus (Campylomormyrus). The hybrids of intergenus hybridizations exhibited different degrees of reduced survival related to the phylogenetic distance of the parent species: hybrids of the crosses between C. rhynchophorus and its sister genus Gnathonemus survived and developed normally. Hybrids between C. rhynchophorus and a Mormyrus species (a more basal clade compared to Campylomormyrus s) survived up to 42 days and developed many malformations, e.g., at the level of the unpaired fins. Hybrids between C. numenius and Hippopotamyrus pictus (a derived clade, only distantly related to Campylomormyrus) only survived for two days during embryological development. Seven different hybrid combinations among five Campylomormyrus species (C. tamandua, C. compressirostris, C. tshokwe, C. rhynchophorus, C. numenius) were performed. The aim of the hybridizations was to combine species with (1) either caudal or rostral position of the main stalk innervating the electrocytes in the electric organ and (2) short, median or long duration of their EOD. The hybrids, though they are still juveniles, show very interesting features concerning electrocyte geometry as well as EOD form and duration: the caudal position of the stalk is prevailing over the rostral position, and the penetration of the stalk is dominant over the non-penetrating feature (in the Campylomormyrus hybrids); in the hybrid between C. rhynchophorus and Gnathonemus petersii it is the opposite. When crossing species with long and short EODs, it is always the long duration EOD that is expressed in the hybrids. The F1-Hybrids of the cross C. tamandua × C. compressirostris are fertile: viable F2-fish could be obtained with artificial reproduction.

 

  1. Lebonguy Augustin Aimé, Goma-Tchimbakala Joseph, Miambi E. and Keleke Simon, 2017. Isolation and characterization of petroleum product emulsifying Pseudomonas strains from a generating set fuel tank. African Journal of Microbiology Research. Vol. 11(22), p. 920-926.

 

  • : This study characterized microbial strains isolated from diesel fuel samples collected from the tank of a generating set at the Institute of Research for Development in Pointe-Noire (Congo). Two bacterial isolates (G2 and G3) were distinguished by their color on agar plates and were characterized by their API 20E biochemical profiles and by 16S rRNA gene sequencing. The phenotypic properties of these isolates were consistent with their assignment to the genus Pseudomonas. Comparative 16S rRNA gene sequence analysis demonstrated that the G2 and G3 isolates were close relatives of P. aeruginosa strain GIM 32 and P. aeruginosa strain NV2, respectively, with 97% sequence identity. These two P. aeruginosa strains were able to grow in a mineral salt medium supplemented with 2% diesel fuel or SAE 90 gear oil as the only source of carbon. P. aeruginosa G3 showed faster growth and was able to emulsify diesel fuel (53%), gasoline (90%) and hexane (95%) more strongly than P. aeruginosa G2.

Mots clés: Pseudomonas, emulsification index, diesel fuel, gasoline, hexane.

 

  1. Soloka Mabika Armel Faly, Moyen Rachel, Nguimbi Etienne, Ahombo Gabriel, Ampa Raoul, Kayath Aimé Christian, Vouidibio Alain, Morabandza Cyr Jonas and Kobawila Simon Charles, 2017. Production, partial purification and based SDS-PAGE Profiles of caseinolytic enzyme in two bacillus strains isolated from fermented cassava leaves “Ntoba mbodi” in Congo Brazzaville. Journal of pure and applied microbiology. Vol. 11(1), p. 77-86.

 

Résumé: Two Bacillus strains isolated from Ntoba mbodi : Bacillus megaterium (B.me NM 02) Bacillus licheniformis (B.li NM01), has shown a significant caseinolytic enzyme activity. We set optimization of growth and enzyme production conditions. Several parameters have been optimized: temperature, pH, various types of media, carbon and nitrogen sources. In both strains, growth is possible from 25 to 60°C with an optimum temperature at 37°C for B.li and at 35°C for B.me. Enzyme production was observed from 25 to 55°C with an optimum temperature at 30°C for B.li. Enzyme production was observed from 25 to 50°C with an optimum temperature of 35°C in B.me. For pH, growth and enzyme production can be at 5,7 and 9 with an optimum at 7 for both strains. The I.B medium is better for growth and enzyme production than TSB for B.li and B.me. Among the carbon sources used, fructose is better for growth after 48 hours of incubation in both strains (B.li; 0,93±0,001, B.me:0,928±0,002), but for enzyme production fructose remains the best carbon sources for B.li (14,33±1,24), while starch is the best source of growth is the yeast extracts (B.li: 0,969±0,015, B.me: 0,952±0,01). For enzyme production, the two sources can be used for B.li, (14,333±1,247) but for B.me (14,333±0,471) only the yeast extracts is the best as well as for growth and enzyme production. Furthermore, in both strains the produced enzyme was partially by using ammonium sulfate precipitation, and SDS-PAGE has been hold, profiles of specific bands are useful to give more information and differentiate the two strains  

  • : Optimization, caseinolytic enzyme, Ntoba mbodi, Bacillus licheniformis, Bacillus megaterium

 

 

Mise  à jour le : 25/07/2019
par la rédaction à 12h00mn
 
  1. Loumouamou Aubin Nestor, Bikindou Kévin, Ntalani Hermeline, Silou Thomas, Chalard Pierre, Ombeline Danton, Delort Laeticia, Decombat Caroline, Caldefie-Chezet Florence, Rubat-Coudert Cathérine and Figueredo Gilles, 2017. Evaluation of the correlation between the chemical profile and the antalgic and anti-proliferative activities of essential oil of Elionurus hensii K. Schum.  Net Jouanals. Advancement in Medicinal Plant Research. Vol. 5(3), p. 41-45.

 

Résumé : Elionurus hensii is usually used by peasant populations as a théiforme drink to relieve aches. The aim of this study was to evaluate the antalgic activity (AA) and antiproliferative activity (ATA) of essential oil of Elionurus hensii (VEH). Essential oils from the aerial parts and roots was extracted by hydrodistillation and analyzed by GC and GC/MS. AA was examined by using test cramps. This method consists in inducing cramps in the mouse by intraperitoneal injection of  0.6% acetic acid solution and to determine any inhibition of the cramps by the compounds contained in the VEH. Cytotoxicity of the essential oil was evaluated in order to assess their ATA on cancer cells MCF-7 using resazurin test. The study was carried out by considering 6 samples of VEH whose contents of major compounds vary. The major constituents are p-menthadienol isomes and limonene for samples from the aerial part, aristolone and limonene for samples from the roots. The most significant AA (inhibition percentage = 56.41%) was observed with a VEH containing p-menthadienol isomers (40.25%) and limonene (15.85%). The VEH containing limonene (20.21%) and aristolone (15.16%) also inhibit cramps with a percent inhibition of 48%. The pure aristolone extract of the essential oil inhibits to 36%. These first results confirm the traditional use of Elionurus hensii by peasant populations. The results of the resazurin test showed that the ATA is dose-dependent VEH from roots, exhibited better anti-proliferative activity compared to the VEH from the aerial part. However, this activity is low.

  • : Elionurus hensii, essential oil, chemical compounds, GC/MS analysis antalgic and anti-proliferative activities.

 

  1. Loumouamou Aubin Nestor, Bikindou Kévin, Nakavoua Aristide Herlyn Wilfred, Malonda Lucie Carine,  Silou Thomas, Chalard Pierre et Figueredo Gilles, 2017. Caractérisation physicochimique et profil chimique de l’huile essentielle d’Elionurus Hensii du Congo Brazzaville. Afrique Science 13(5), 319-329.

 

  • : Cette recherché vise à réaliser l’étude de la variation saisonnière des caractéristiques physico-chimiques et de la composition chimique des extraits volatils d’Elionurus hensii. Les échantillons d’huile essentielle, obtenus par entrainement à la vapeur de la matière végétale (partie aérienne et racines) récoltée à différentes périodes de l’année, ont été analysés par GC et GC-MS. Les caractéristiques physicochimiques, comme la densité, l’indice d’acide et la pouvoir rotatoire, ont été déterminées suivant les normes AFNOR. Le traitement statistiques des données issues de l’analyse de la composition chimique de 15 échantillons d’huile essentielle, par l’Analyse en Composante Factorielle (ACP), la Classification Hiérarchique Ascendante (CAH) et le t-test de student, a permis d’identifier différents profils chimiques. L’huile essentielle de la partie aérienne présente un profil chimique à p-menthadiènols majoritaires (cis et trans-p-mentha-2,8-dièn-1-ol, cis et trans-p-mentha-1(7),  8-dièn-2-ol) permanent toute l’année et un profil à limonène majoritaire (12,83% - 20,47%) pour certains échantillons. L’huile essentielle des racines présentent également deux profils chimiques : un profil à limonène majoritaire (20,21% - 30,44%) et un autre à aristolone majoritaire (38,77% - 49,02%). Les caractéristiques physico-chimiques varient très peu et leurs valeurs sont conformes à celles des huiles essentielles de la plupart des autres espèces. La mesure du pouvoir a permis de constater que l’huile essentielle de la partie aérienne est dextrogyre et celle des racines est lévogyre, ce qui constitue une indication majeure pour le contrôle qualité de cette huile.
  •  : Elionurus hensii, profil chimique, caractéristiques physicochimiques,

           p-menthadienols, aristolone.

 

  1. Jordon D. Hemingway, Enno Schefuß, Robert G.M. Spencer, Bienvenu Jean Dinga, Timothy I. Eglintonf, Cameron McIntyre, Valier V. Galy, 2017. Hydrologic controls on seasonal and inter-annual variability of Congo River particulate organic matter source and reservoir age. Chemical Geology 466 (2017) 454–465.

 

  • :  We present dissolved organic carbon (DOC) concentrations, particulate organic matter (POM) composition, (δ13C, δ15N, Δ14C, N/C), and particulate glycerol dialkyl glycerol tetraether (GDGT) distributions from a 34- month time-series near the mouth of the Congo River. An end-member mixing model using δ13C and N/C indicates that exported POM is consistently dominated by C3 rainforest soil sources, with increasing contribution from C3 vegetation and decreasing contribution from phytoplankton at high discharge. Large C4 inputs are never observed despite covering ≈13% of the catchment. Low and variable Δ14C values during 2011 [annual mean= (−148 ± 82) ‰], when discharge from left-bank tributaries located in the southern hemisphere reached record lows, likely reflect a bias toward pre-aged POM derived from the Cuvette Congolaise swamp forest. In contrast, Δ14C values were stable near −50‰ between January and June 2013, when left-bank discharge was highest. We suggest that headwater POM is replaced and/or diluted by C3 vegetation and pre aged soils during transit through the Cuvette Congolaise, whereas left-bank tributaries export significantly less pre-aged material. GDGT distributions provide further evidence for seasonal and inter-annual variability in soil provenance. The cyclization of branched tetraethers and the GDGT-0 to crenarchaeol ratio are positively correlated with discharge (r ≥0.70; p-value ≤4.3 ×10−5) due to the incorporation of swamp-forest soils when discharge from right-bank tributaries located in the northern hemisphere is high. Both metrics reach record lows during 2013, supporting our interpretation of increased left-bank contribution at this time. We conclude that hydrologic variability is a major control of POM provenance in the Congo River Basin and that tropical wetlands can be a significant POM source despite their small geographic coverage.
  • : Biomarkers Congo River GDGTs Particulate organic matter Radiocarbon.

 

  1. Djama Louis Marie Joachim, Matiaba Bazika Ulrich Verne, Boudzoumou Florent, Kinga Mouzeo, 2018. Petrology and geodynamic context of Metabasic Rocks of Nemba Complex in the west Congo fold (Republic of Congo). International Journal of Geosciences, 9, p. 1-18.  

 

  • : The West Congo belt contains Paleoproterozoic and Neoproterozoic Units which are deformed during Panafrican event. The Neoproterozoic Unit contains rift and post rift deposits. The rift formation is made of metabasite, volcanic and volcano-sedimentary rocks. The metabasite constitutes the Nemba Com-plex which is considered put into place in a continental or oceanic context. Samples from Nemba Complex collected along the “Congo ocean railway rea-lignment” are analyzed. Major elements indicate a low potassic su balkaline af-finity of the samples. Classification diagrams based of major elements shows that the rocks are a tholeiitic serie constituted of andesitic basalts, sub-alkaline andesitic basalts and a sub-alkaline to alkaline basalts. Some samples with a calc-alkaline signature indicate a crustal contamination. The traces elements plots indicate that the rocks are the MORB. The spectrum of multi-elements is characteristic of continental rocks with a lithospheric origin. This is an agreement with many works on the Nemba Complex and the alkali plutons and acid volcanic rocks associated which attribute there a rift context.

 

  • : West Congo, Neoproterozoic, Tholeiite, Andesitic Basalts, Basalts, MORB, Continental Rocks

 

  1. Tchibota Poaty Lodvert, Ulman Kanchan, Serlani Nicola, Mpassi-Mabiala Bernard, Gebauer Ralph, 2018. Characterization of peroxo reaction intermediates in the water oxidation process on hermatite surfaces. J Mol Model (2018) 24: 284.

 

Résumé: We use density functional theory-based calculations to study structural, electronic, and magnetic properties of two key reaction intermediates on a hematite, α-Fe2O3, photoanode during the solar-driven water splitting reaction. Both intermediates contain an oxygen atom bonded to a surface iron atom. In one case, the adsorbed oxygen also forms a peroxo bond with a lattice oxygen from hematite; in the second case no such bond is formed. Both configurations are energetically equivalent and are related to the overpotential-determining step in the oxygen evolution reaction. The calculated reaction path for the breaking of the peroxo bond shows a barrier of about 0.86 eV for the transformation between the two intermediates. We explain this high barrier with the drastically different electronic and magnetic structure, which we also analyze using maximally localized Wannier functions. Photo-generated electron holes are shown to localize preferentially close to the reaction center at the surface in both configurations. In the case of the oxo species, this localization favors subsequent electron transfer steps during the oxygen evolution cycle. In the case of the peroxo configuration, this fact together with the high barrier for breaking the oxygen–oxygen bond indicates a possible loss mechanism due to hole trapping.

Mots clés:Hematite · Water splitting · Density functional theory

 

 

  1. H.B. Mabiala-Poaty, D.H. Douma, B. Mpassi-Mabiala, R. E. Mapasha, 2018. Structural and electronic properties of SnS2 stacked nanosheets: An ab-initio study. Journal of Physics and Chemistry of Solids. P. 211-217.

 

  • : We present an ab-initio study of the structural and electronic properties of SnS2 stacked nanosheets using the standard LDA and GGA functionals as well as the newly developed variants of the non-local van der Waals (vdW) exchange correlation functionals, namely vdW-DF-revPBE and vdW-DF2-C09. We have examined different stacking configurations of the two, three and four SnS2 layers. The GGA-PBE functional fails to describe the interlayer binding energies and interlayer spacing of SnS2 nanosheets, while a good agreement is observed between the calculated and available experimental values when the van der Waals corrected functionals are used, mostly the vdW-DF2-C09. It is found that the interlayer interactions in the SnS2 films are not only vdW type but, the overlap of wave functions of neighboring layers have to be taken into account. We have observed a systematic reduction in the band gap with the increase in the number of stacked layers. This can be another way of controlling the band gap of SnS2 nanosheets as required for electronic devices.

Mots clés: DFT – Nanosheets - Van der Waals exchange correlation functional - Electronic structure - 2D materials - SnS2

 

  1. H.B. Mabiala-Poaty, D.H. Douma, B.R. Malonda-Boungou, R. E. Mapasha B. Mpassi-Mabiala, 2018. First-principles studies of SnS2, MoS2 and WS2 stacked van der Waals hetero-multilayers. Computational Condensed Matter. P. 1-10.

 

  • : We present the energetics, structural and electronic properties of SnS2 monolayer stacked with MoS2 and WS2 monolayers making the van der Waals hetero-layers using the first-principles methods. The exchange-correlation functionals used are the LDA, GGA functionals as well as the newly developed variants of non local van derWaals (vdW) exchange-correlation functionals, namely vdW-DF-revPBE and vdW-DF2-C09. We also considered the combinations of hetero-layers that involve all the three SnS2, MoS2 and WS2 stacked together. All the investigated hetero-layers have a short decay (offset) of the equilibrium lattice parameters compared to the SnS2 single layer one. Except for the GGA-PBE functional, all the functionals predict the interlayer distances closer to the previous theoretical and experimental studies. The hetero-layers that have relative low binding energies are indirect band gap semiconductors, while those with dramatically high binding energies are weakly or strongly metallic. This study gave another avenue of altering the energetics and electronic properties of SnS2 monolayer through vertical stacking with MoS2 and WS2. The variation in band gap enables these newly predicted hetero-layers to be suitable candidates for designing novel devices for nanoelectronic and optoelectronic technology, which includes energy storage, photodetectors, thermophotovoltaic.

Mots clés: SnS2 - MoS2 - WS2 - Van der Waals hetero-layers - Electronic properties - Van der Waals exchange-correlation – functional - First-principles methods.

 

  1. Phwey S. Gil, Daniel J. Lacks, Pietro Parisse, Loredana Casalis and Maryse D. Nkoua Ngavouka, 2018. Single-stranded DNA oligomer brush structure is dominated by intramolecular interactions mediated by the ion environment. Soft Matter-Journal.

 

  • : Single-stranded DNA (ssDNA) brushes, in which ssDNA oligomers are tethered to surfaces in dense monolayers, are being investigated for potential biosensing applications. The structure of the brush can affect the selectivity and the hybridization efficiency of the device. The structure is commonly thought to result from the balance of intramolecular interactions, intermolecular interactions within the monolayer, and molecule- surface interactions. Here, we test the hypothesis that ssDNA oligomer brush structure is dominated by intramolecular interactions. We use AFM to measure the height to an ssDNA brush and molecular dynamics to simulate the end-to-end distance, both as a function of ionic strength of the surrounding solution. The brush height and the molecule end-to-end distance match quantitatively, providing evidence that the brush structure is dominated by intramolecular interactions (mediated by ions). The physical basic of the intramolecular interactions is elucidated by the simulations.

 

  1. Timothée Miyouna, Hardy Medry Dieu-Veill Nkodia, Olivier Florent Essouli, Moussa Dabo, Florent Boudzoumou and Damien Delvaux, 2018. Strike-slip deformation in the Inkisi formation, Brazzaville, Republic of Congo. Cogent geosciences. Pg 1-32.

 

  • : Evidence of strike-slip deformation in the Inkisi Formation was over-looked for a long time. After controversial characterization, this paper demonstrates that the Inkisi Formation underwent to least two phases of strike-slip deformation accompanied with a compressive component, which created faults that help determine paleostress. Field observations permitted to characterize NW-SE trends sinistral strike-slip faults systems and NE-SW oriented dextral strike-slip faults systems. The strike-slip faults are associated with flower structures in profile view and with damage zones along tips, wall and linking zones in plan view. Both faults systems (sinistral and dextral) initiated from joints, which show similar orientations with faults. Many kinematic indicators of slip sense or extension have enabled to determine the stress stages and the evolution of the structures. The first tectonic phase has a horizontal maximum principal compressive stress d1 of 264°± 22,3/12 potentially results from the intraplate stress propagation, due to the opening of the Southern Atlantic Ocean.
  • : strike-slip faults; joints; damage zones; plumose structures; flower structure; paleostress; Inkisi formation; Congo.

 

  1. Jean Luc Dimi and Texance Mbaya, 2018. Dynamics analysis of stochastic tuberculosis model transmission with immune response. AIMS Mathematics. 3(3): 391-408.

 

  • : In this paper we extend the tuberculosis epidemic model from a deterministic framework to a deterministic model with immunue response and after to stochastic one. We formulate it as a stochastic differential equation. We, then, etablish the stabilities of different equilibria, and give conditions for extinction and persistence of the desease.

Mots clés: nonlinear epidemic model; Lyapounov function; stochastic asymptotic stability; It ˆo ’s formula

 

  1. Augustin Aimé Lebonguy, Joseph Goma-Tchimbakala et Simon Kéléké , 2018. Tolérance aux métaux, aux hydrocarbures et aux antibiotiques de deux souches de Pseudomonas aeruginosa neutrophiles isolées du gasoil. Afrique SCIENCE. P. 158-170.

 

  • : L’objectif de cette étude est d’évaluer la multi-résistance aux hydrocarbures, aux métaux et aux antibiotiques des souches de Pseudomonas aeruginosa G2 et G3 isolées du gasoil. L’effet du pH et de la concentration en NaCl sur la croissance des deux souches en milieu liquide a été préalablement étudié. Les résultats montrent que les deux souches sont neutrophiles. La souche P. aeruginosa G2 tolère jusqu’à 40 g/L de NaCl tandis que la souche G3 tolère moins de 20 g/L. L’étude de la tolérance aux hydrocarbures par les méthodes de diffusion sur gélose et de spot montre que les deux souches tolèrent 100% de gasoil et d’huile SAE 90. Cependant, l’essence, le toluène et le xylène inhibent la croissance de P. aeruginosa G3 tandis que seul le xylène inhibe la croissance de P. aeruginosa G2. Les deux souches de P. aeruginosa G2 et G3 résistent, respectivement aux CuCl2, SnCl2, NiCl2, CoCl2, ZnSO4 et SnCl2, ZnSO4, FeSO4. Enfin, l’antibiogramme montre que les deux souches sont résistantes à l’ampicilline et la spiramycine mais sensibles au chloramphénicol à 0,5 ‰. Seule la souche P. aeruginosa G2 résiste à la kanamycine. Ainsi, cette étude montre que les deux souches de P. aeruginosa sont multi-résistantes aux hydrocarbures, aux métaux et aux antibiotiques. Ces caractéristiques sont très importantes dans leur utilisation potentielle dans la bioremédiation des sites co-contaminés par ces polluants.

Mots-clés : Pseudomonas aeruginosa, tolérance, multirésistance, polluants.

 

  1. Victor Mamonekene, Armel Ibala Zamba, and Melanie l.j. Stiassny, 2018. A new small barb (Cyprininae: Smiliogastrini) from the Louesse, Lekoumou (upper Niari basin), and Djoulou (upper Ogowe basin) rivers in the Republic of Congo, west-central Africa. AMERICAN MUSEUM NOVITATES, Number 3917, 16 pp.

 

  •  :  A new species of smiliogastrin cyprinid is described from the Louesse, Lekoumou (upper Niari basin), and Djoulou (upper Ogowe basin) rivers in the Republic of Congo, west-central Africa. The new species is readily distinguished from congeners by the presence of a flexible, weakly ossified and smooth bordered last unbranched dorsal-fin ray, well-developed barbels, and a straight and complete lateral line in combination with a characteristic pigmentation patterning consisting of a distinctive, rounded black spot at the base of and extending over the first rays of the anal fin and a prominent, darkly pigmented blotch over the base of the anterior dorsal-fin rays. A combination of morphological features and pigmentation patterning that appears to be unique among Enteromius. The new species is widespread throughout the Louesse-Djoulou region, and the fact that such a seemingly common species has gone undetected until now serves to underscore how poorly known this region of the Republic of Congo remains.

 

  1. Jean Armand Paka, Destyles Van Kombyla, Barthel Koua Bita, Jean Bienvenu Dinga, Salisous Yallo Mouhamed, Ernest Amoussou et Marie Joseph Samba-Kimbata, 2018. Fluctuations des précipitations et des écoulements dans le Bassin versant de l’Alima à Tchikapika au Congo-Brazzaville en Afrique Centrale de 1960 – 1993. Rev. Ivoir. Sci. Technol, 32 (2018) 85-97.

 

  • : L’étude de la variabilité des précipitations et des écoulements dans le bassin de la rivière Alimaz à Tchikapika porte sur les chroniques de la période 1960-1993. Les données hydrométriques enregistrées à la station de Tchikapika ont été soumises à deux tests non paramétriques afin de déterminer les ruptures de stationnarité et leur degré de signification. L’analyse révèle que la modification du régime des précipitations s’est traduite plus nettement par une diminution brutale des quantités d’eau précipitée au cours de la décennie 70. La baisse pluviométrique concerne les hauteurs mensuelles des mois de juin, juillet, août et septembre (donc au cœur de la saison sèche) qui sont de moins en mois arrosés. Par ailleurs, les effets de cette importante baisse pluviométrique sur les écoulements sont très remarquables. Le déficit pluviométrique est largement amplifié dans les écoulements et les recherches de la rivière. Il représente environ le tiers (1/3) dy déficit d’écoulement dans la quasi-totalité des rivières du Plateau Téké et même du Congo en général.
  • -clés : bassin versant Alima, variabilité pluviométrique, déficit d’écoulement, Congo.

 

  1. Dallou Guy Blanchard, Ngoa Engola Louis, Abdourahimi, Bongue Daniel, Saïdou, Ndjana Nkoulou II Joseph Emmanuel, Kankeu Boniface and Kwato Njock Moïse Godfroy, 2018Environmental Pollution by Heavy Metals in the Gold Mining Region of East Cameroon. American Journal of Environmental Sciences. 2018, 14 (5): 212.225

 

  • : The main objective of this study is to assess the level of heavy metals pollution in soil samples collected around gold mines located in Betaré Oya (BO) and Batouri (BA) in Eastern Cameroon. Elemental analysis of soil samples was carried out using Quant´X EDXRF spectrometer. Its sensitivity and accuracy were increased by using the Fundamental Parameter approach for quantification of the results. Analysis results showed high content of iron (39300±200 ppm), the presence of manganese (730±70 ppm), arsenic (4±2 ppm), zirconium (314±4 ppm) and lead (79±9 ppm) as compared to worldwide average upper continental crust (UCC). The mean Enrichment Factors (EF) decrease as Pb>As>Zr>Mn>Fe>Y>Ga>Zn>Cu>Ni> Rb>Sr>Sn>Ba in agreement with the Contamination Factors (CF). The values of pollution load index (PLI) were found to be low in all the studied samples and indicate that the studied sites in Bétaré Oya and Batouri are in low pollution status regarding the total of the studied metals. Results of this study pointed out that soils examined in the gold mining areas of Eastern Cameroon are polluted by heavy metals. It is therefore important that measures should be geared towards strengthening the monitoring of mining areas to stem down the level of contamination of soil. Phytoremediation of sites after closing open pits or the biogeosystem method would be a suitable way of regulation of the studies areas.
  • : Gold Mine, X-Ray Fluorescence, Heavy Metals, Enrichment Factor, Pollution Load Index

 

  1. Václav Gvoždík, Matej Dolinay, Ange-G. Zassi-Boulou and Gabriel Badjedjea Babangenge,   2018.  New data on Trachylepis makolowodei from Central Africa. Herpetology Notes, volume 11: 515-518 (2018)

 

  1. Zassi-Boulou A.G., Goma-Tchimbakala J., Ibala Zamba A., Mavoungou L.B., V. Gvoždík et Jackson K., 2018. Distribution spatiale de la diversité des ophidiens dans le département du Pool, République du Congo. Annales de l’Université Marien NGOUABI, 2018 ; 18 (1) : 1-15 Sciences et Techniques ISSN.

 

  • : La présente étude a été menée dans les Sous-préfectures de Ngabé, d’Ignié et de Goma Tsé-Tsé dans le département du Pool. L’objectif était de faire l’inventaire des serpents et appréhender leur répartition spatiale à partir de cinq habitats écologiquement différents (forêts naturelles, forêts plantées, savanes, milieux humides). Deux méthodes (active et passive) ont été utilisées pour l’échantillonnage des spécimens dans les différents habitats. Ces méthodes ont permis d’inventorier 21 spécimens d’ophidiens repartis en 15 espèces, 12 genres, 6 sous-familles et 5 familles. Dans cette étude, les espèces appartenant à la famille des Colubridae (42,86%) et des Lamprophiidae (28,57%) constituent la plus grande partie de la diversité des ophidiens échantillonnés. Les espèces Boaedon fuliginosus et Causus maculatus ont été les plus représentatives dans les collectes effectuées dans les trois sous-préfectures. En dépit de la forte dégradation des habitats, ces résultats ont révélé l’existence d’une remarquable richesse et diversité ophidiennes dans cette partie du département du Pool en République du Congo.

Mots-clés : Diversité, ophidien, serpents, richesse spécifique, Congo

 

  1. Hanlie M. Engelbrecht, William R. Branch, Eli Greenbaum, Graham J. Alexander, Kate Jackson, Marius Burger, Werner Conradie, Chifundera Kusamba, Ange-Ghislain Zassi-Boulou, Krystal A. Tolley, 2019. Diversifying into the branches: Species boundaries in African green and bush snakes, Philothamnus (Serpentes: Colubridae). Molecular Phylogenetics and Evolution 130 (2019) p. 357–365.

 

  • : The African green and bush snakes of the genus Philothamnus currently comprises 21 species and three subspecies and occurs throughout sub-Saharan Africa. The genus has been the subject of previous taxonomic revisions based on traditional morphological characters and limited genetic assessment, and may not reflect their evolutionary history. Indeed, previous findings based on phylogenetics show discordant results of interspecific relationships and question the monophyly of the genus, although taxon sampling has been limited to date. We investigated phylogenetic affinities within Philothamnus with more inclusive genetic and geographical sampling, with the aim of better understanding their evolutionary history, so that future taxonomic revision of Philothamnus can be better informed. Species relationships were examined within a phylogenetic context and sampling included 133 ingroup samples from 16 taxa. Phylogenies were constructed in Bayesian and likelihood frameworks using three mitochondrial (16S, cyt b and ND4) and two nuclear (c-mos and RAG1) markers. Competing hypotheses relating to the monophyly of the genus were tested with a Shimodaira-Hasegawa test. To examine species boundaries, Bayesian General Mixed Yule Coalescent Model and multirate Poisson Tree Processes analyses were conducted. In addition, a barcoding approach was used to further clarify species-level relationships by comparing frequency distributions between intra- and interspecific sequence divergence. The genus was recovered as monophyletic; however, species-delimitation results suggest that the current taxonomy does not reflect the evolutionary history of this group. For example, Philothamnus s. semivariegatus is paraphyletic, with at least four distinct clades. Philothamnus carinatus consists of two cryptic (sister) lineages from Central and West Africa that are deeply divergent, suggesting a long history of isolation between those regions. Furthermore, the subspecies P. n. natalensis and P. n. occidentalis show strong support for species-level divergence, which reflects their morphological and ecological differences. Accordingly, we elevate P. occidentalis nov. comb. to a full species. A fully informed taxonomic revision of these taxa will require additional morphological and ecological data for corroboration, but it seems that the morphological characters (e.g. scalation, dentition) used to describe these species to date are labile within and between species. This most likely has clouded our understanding of the species boundaries within the genus. Our phylogeny and species-delimitation analyses should provide a sounder framework for taxonomy, but may also prove useful toward understanding the morphological adaptations of these species to their respective habitats.

 

  1. Gregory F.M. Jongsma, Michael F. Barej, Christopher D. Barratt, Marius Burger, Werner Conradie, Raffael Ernst, Eli Greenbaumi, Mareike Hirschfeld, Adam D. Leachéj, Johannes Penner, Daniel M. Portik, Ange-Ghislain Zassi-Boulou, Mark-Oliver Rödel, David C. Blackburn , 2018. Diversity and biogeography of frogs in the genus Amnirana (Anura: Ranidae) across sub-Saharan Africa. Molecular Phylogenetics and Evolution 120 (2018) p. 274-285.

 

  • :  Frogs in the genus Amnirana (family Ranidae) are widely distributed across sub-Saharan Africa and present a model system for exploring the relationship between diversification and geography across the continent. Using multiple loci from the mitochondrial (16S) and nuclear genomes (DISP2, FICD, KIAA2013, REV3L), we generated a strongly supported species-level phylogeny that provides insights into the continental biogeography of African species of Amnirana, which form a monophyletic group within the genus. Species delimitation analyses suggest that there may be as many as seven additional species of Amnirana in Africa. The biogeographic history of Amnirana is marked by several dispersal and vicariance events, including dispersal from the Lower Guinean Forest into the Congo Basin. In addition, phylogeographic patterns within two widespread species, A. albolabris and A. galamensis, reveal undescribed cryptic diversity. Populations assigned to A. albolabris in western Africa are more closely related to A. fonensis and require recognition as a distinct species. Our analyses reveal that the Lower and Upper Guinean Forest regions served as important centers of interspecific and intraspecific diversifications for Amnirana.

 

  1. Frank Portillo, William R. Branch, Werner Conradie, Mark-Oliver Rödel, Johannes Penner, Michael F. Barej, Chifundera Kusamba, Wandege M. Muninga, Mwenebatu M. Aristote, Aaron M. Bauer, Jean-François Trape, Zoltán T. Nagy, Piero Carlino, Olivier S.G. Pauwels, Michele Menegon, Marius Burger, Tomáš Mazuch, Kate Jackson, Daniel F. Hughes, Mathias Behangana, Ange-Ghislain Zassi-Boulou, Eli Greenbaum, 2018. Phylogeny and biogeography of the African burrowing snake subfamily Aparallactinae (Squamata: Lamprophiidae). Molecular Phylogenetics and Evolution 127 (2018) p. 288–303.

 

  • :  Members of the snake subfamily Aparallactinae occur in various habitats throughout sub-Saharan Africa. The monophyly of aparallactine snakes is well established, but relationships within the subfamily are poorly known. We sampled 158 individuals from six of eight aparallactine genera in sub-Saharan Africa. We employed concatenated gene-tree analyses, divergence dating approaches, and ancestral-area reconstructions to infer phylogenies and biogeographic patterns with a multi-locus data set consisting of three mitochondrial (16S, cyt b, and ND4) and two nuclear genes (c-mos and RAG1). As a result, we uncover several cryptic lineages and elevate a lineage of Polemon to full species status. Diversification occurred predominantly during the Miocene, with a few speciation events occurring subsequently in the Pliocene and Pleistocene. Biogeographic analyses suggested that the Zambezian biogeographic region, comprising grasslands and woodlands, facilitated radiations, vicariance, and dispersal for many aparallactines. Moreover, the geographic distributions of many forest species were fragmented during xeric and cooler conditions, which likely led to diversification events. Biogeographic patterns of aparallactine snakes are consistent with previous studies of other sub-Saharan herpetofauna.

 

  1. Aulne Lérège Batiabo Mikembi, Armel Ibala Zamba, Victor Mamonekene, Hélène Dembe Louvinguila Tenda, Freedom Honest Poaty Ngot, Joseph Vouidibio, 2019. Relations longueurs-poids et coefficients de condition pour 13 espèces de poisons de la rivière Dzoumouna, affluent du cours inférieur du fleuve Congo (République du Congo). Journal of Animal & Plant Sciences, 2019. Vol, 33, Issue 1: p. 6384-6393.

 

  • : Objectif : La présente étude décrit les relations longueur-poids (RLPs) et les facteurs de condition (K) de Brycinus bimaculatus, B. grandisquamis, B. imberi, Bryconaethiops yseuxi, Clypeobarbus pleuropholis, Distichodus fasciolatus, Hemichromis elongatus, Labeo cychlorhynchus, Micralestes acutidens, M. humilis, Petrocephalus christyi, Phago boulengeri et Raiamas christyi, 13 espèces les plus abondantes dans la rivière Dzoumouna, petit affluent de la rive droite du fleuve Congo en République du Congo. Méthodologie et Résultats : Entre janvier 2015 et juillet 2018, des échantillonnages des poissons ont été réalisés dans 28 stations dans la rivière Dzoumouna. Chacune des stations a été échantillonnée suivant une méthode de pêche standardisée à l’aide de cinq filets maillants monofilament de 10, 12, 15 20 et 30 mm de côté de maille. Seules les espèces ayant au moins 10 spécimens ont été étudiées. Les relations Longueur-poids ont été calculées en utilisant l’équation P = aLSb et leurs coefficients de condition en utilisant l’équation K = (100P ⁄ LSb). Au total, 205 spécimens, réparties en 4 ordres, 5 familles, 10 genres et 13 espèces ont été utilisés dans le cadre de cette. Le coefficient d’allométrie b de la relation poids-longueur a varié entre 2,514 chez Phago boulengeri et 3,560 chez Brycinus imberi avec une moyenne de 2,901 ± 0,326. Six espèces ont une croissance isométrique, cinq ont une croissance allométrique négative et chez les deux espèces restantes, la croissance est de type allométrique positive. Le coefficient de détermination r2est significatif et varie de 0,942 chez Micralestes humilis et 0,996 chez Raiamas christyi avec une valeur moyenne de 0,976 ± 0,016. Le facteur de condition varie en moyenne de 9,428 ± 0,344 pour Brycinus imberi et de83,560 ± 5,994 pour Labeo cychlorhynchus. Conclusion et application des résultats : Ces résultats contribuent à la connaissance de la biologie des poissons du bassin du Congo. Elle fournit très particulièrement une base de données sur les relations longueur-poids et coefficients de condition de 13 espèces les plus abondantes de rivière Dzoumouna. Length-weight relationships and condition factors of 13 fish species from the Dzoumouna River, middle Congo River basin (Republic of Congo)

 

Mots clés : Poissons, croissance, coefficient de condition, rivière Dzoumouna, bassin du Congo.

 

  1. Christian Aimé Kayath, Armel Ibala Zamba , Joseph Goma-Tchimbakala, Victor Mamonekene , Gloire Moniceth Mombo Makanga, Augustin Aimé Lebonguy and Etienne Nguimbi , 2019. Microbiota Landscape of gut system of guppy Fish (Poecilia reticulata) plays an Oustanding role in adaptation mechanisms. International Journal of Microbiology. P. 1-10.

 

  •  : Microbial consortium that is present in fish gut systems works together to achieve unknown specific roles. Here, we collected guppy fish from hydrocarbon- and trace metal-contaminated wastewater to assess the relationships between gut microbiota and host fish adaptation. Targeted genes and 16S rRNA amplicon sequencing have been used to identify gut bacteria of guppies. Mineral-conditioned medium contributes to identify bacteria with the ability to grow and/or to tolerate hydrocarbon and trace metals. Additionally, trace metals’ tolerance minimum inhibitory concentration (MIC) of microbiota was evaluated. We first isolated bacteria from the gut system, and we showed that Bacillus spp., Staphylococcus spp., Salmonella spp., Pseudomonas spp., Citrobacter spp., enteric ssp.arizonae sp., Enterobacted spp., and Acinetobacter spp., are part of guppy gut microbiota. Some representative species are able to degrade and/or tolerate gasoline and/or diesel fuel hydrocarbons. Toterance to trace metals was observed in Gram-positive and Gram-negative bacteria. We showed that minimal inhibitory concentration (MIC) of some microbiota isolated from gut systems has been found including for mercury (Hg) between 2 and 4%, cobalt (Co) Co (2 and 5%), Zinc (Zn) (9 and 18%), and plomb (Pb) (22 and 27%). Zn and Pb were the trace metals for which the rate of tolerance was significantly higher. Finally, we showed that cytochrome c oxidase is not interfering in presence of trace metals. The working consortium showed that bacteria should work together to achieve their best. 

 

  1. Basile Guy Richard Bossoto, Olivier Mabiala Mikanou and Apépé Jugendène Nguéngué Louvouandou, 2019. Note on Poisson cohomology on Weil bundles. Anales Polonici Mathematici. P. 1-9.

 

  • The purpose of this note on Poisson cobomology in to show that if M is a Poisson manifold and if A is an Well algebra, then the Weil bundle MA is a Poisson manifold. Therefore, we establish a relationship between Poisson cobomology  with values in A and Poisson cobomology  with real values.

 

  • : Mathematics Subject Classification Prinmary 53D17: Secondary 58A20.

 

  1. Armel Ibala Zamba, Emmanuel Vreven, Victor Mamonekene & Jos Snoeks, 2019. Fish community assemblages in relation to environmental variables in the Lefini River, middle Congo River Basin (Republic of Congo). Scientific paper. Cybium 2019, p. 83-95.

 

  •  : Distribution des communautés des poissons en relation avec les variables de l’environnement dans la rivière Léfini, bassin du Moyen Congo (République du Congo).

La présente étude, l’une des rares investigations sur l’écologie des poissons entreprises en Afrique, a été réalisée dans le bassin de la rivière Léfini, un grand affluent de la rive droite du fleuve Congo en République du Congo. L’étude a été menée dans 12 stations écologiques, réparties sur 103 km le long de la rivière. Chaque station a été échantillonnée huit fois en deux ans, suivant une méthode de pêches standardisées à l’aide des flets maillants monoflaments de 10, 12, 15, 20 et 30 mm de côté de maille. Dix-huit variables de l’environnement ont été mesurées au niveau de chaque station prospectée. Un total de 8698 spécimens, appartenant à 84 espèces, 51 genres et 21 familles, ont été reportés. L’Analyse Canonique de Redondance avec sélection préalable, couplée au test de permutation de Monte Carlo (999 itérations) a identifié 3 variables (température, couverture de la canopée et hauteur de la canopée) exprimant à elles seules 36,9% de la variance totale (p < 0,05). La contribution des deux premiers axes a été significative (F = 1,56 ; p = 0,02). Les populations de poissons sont distribuées suivant cinq types d’habitats : vasque bordée d’herbes ; rive bordée d’herbes ; forestier à grande couverture de la canopée 60,0-67,0% ; forestier à moyenne couverture de la canopée 33,0-48,0% et forestier à faible couverture de la canopée 24,0%. Les indices de la richesse spécifique “S” ont montré la faible diversification des stations herbeuses. Cependant, les valeurs élevées des indices de Shannon H’ (2,64-3,24) et d’équitabilité R (0,73-0,83), dans l’ensemble des stations, indiquent que le tronçon examiné dans le bassin de la rivière Léfini est en bonne santé écologique.

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