Caractères des sols ferrallitiques à plinthite et à pétroplinthite développés sur roches acides dans la zone forestière du sud du Cameroun : comparaison avec les sols développés sur roches basiques

Le Plateau sud-camerounais est une vaste région forestière mollement ondulée sur socle précambrien. Il est constitué de roches métamorphiques acides traversées par des intrusions de syénites alcalines potassiques et des filons de roches basiques. Des évolutions lithodépendantes de la couverture pédologique ont été caractérisées sur gneiss, syénite et amphibolo-pyroxénite. Sur gneiss et sur syénite, les sols présentent la différenciation classique des latérites intertropicales et sont constitués d'une altérite, d'un ensemble glébulaire et d'un ensemble meuble superficiel. Sur roche basique, le profil ne présente qu'une altérite ferruginisée épaisse surmontée par un horizon meuble superficiel. Les résultats de la caractérisation montrent qu'il s'agit de sols acides, désaturés dans les horizons minéraux. L'argilisation est immédiate sur roches basiques alors qu'elle est très progressive sur syénite et intermédiaire sur gneiss. Les oxydes de fer sensu lato s'accumulent fortement dans les ensembles glébulaires du gneiss et de la syénite et dans les altérites ferruginisées de la roche basique. Il s'agit essentiellement du fer s'exprimant sous forme de goethites alumineuses majoritaires auxquelles s'associe de l'hématite dans les matrices les plus rouges des ensembles glébulaires. Les argiles sont constituées majoritairement de phyllites 1/1 et présentent une paragenèse verticale très différenciée : les halloysites sont prépondérantes sur les macrokaolinites à la base des profils tandis que les kaolinites fines prennent le relais dans les parties sommitales. (Résumé d'auteur

The Monogenean Parasite Fauna of Cichlids: A Potential Tool for Host Biogeography

We discuss geographical distribution and phylogeny of Dactylogyridea (Monogenea) parasitizing Cichlidae to elucidate their hosts' history. Although mesoparasitic Monogenea (Enterogyrus spp.) show typical vicariant distribution, ectoparasitic representatives from different continents are not considered sister taxa, hence their distribution cannot result from vicariance alone. Because of the close host-parasite relationship, this might indicate that present-day cichlid distribution may also reflect dispersal through coastal or brackish waters. Loss of ectoparasites during transoceanic migration, followed by lateral transfer from other fish families might explain extant host-parasite associations. Because of its mesoparasitic nature, hence not subject to salinity variations of the host's environment, Enterogyrus could have survived marine migrations, intolerable for ectoparasites. Host-switches and salinity transitions may be invoked to explain the pattern revealed by a preliminary morphological phylogeny of monogenean genera from Cichlidae and other selected Monogenea genera, rendering the parasite distribution explicable under both vicariance and dispersal. Testable hypotheses are put forward in this parasitological approach to cichlid biogeography. Along with more comprehensive in-depth morphological phylogeny, comparison with molecular data, clarifying dactylogyridean evolution on different continents and from various fish families, and providing temporal information on host-parasite history, are needed to discriminate between the possible scenarios

Effects of some physical and chemical characteristics of soil on productivity and yield of cowpea (Vigna unguiculata L. Walp.) in coastal region (Cameroon)

Studies were conducted to assess the response of cowpea (Vigna unguiculata L. Walp) to some physical and chemical characteristics of soil in coastal region (Cameroon). The cowpea variety used in this trial was Tsacre, planted at a spacing of 80 cm × 80 cm. The experimental design was a randomized complete block comprising of five plots with three replicates. Productivity parameters (dry weight aerial parts, roots dry weight, abortion seeds rate, number of flowering per plant, flowering rate) and yield components (number of seeds per pod, number of pod per plant, grain yield, pod yield and weight of 1000 seeds) were determined. Soil samples were taken randomly from depths of 0 - 30 and 30 - 60 cm before seeds sowing. The results showed that the plot with the highest percentage of sand (71.80%), the lowest percentage of clay (21.00%) and silt (7.20%) and with the highest amount of organic matter (10.26%), exchange potassium (0.36 g Kg-1), calcium (0.49 g Kg-1) and magnesium (0.46 g Kg-1) increased significantly (

Cerium anomalies in lateritic profiles

L'étude minéralogique et géochimique des terres rares permet de définir le comportement du cérium dans 4 profils latéritiques du Camerou

Alloantibodies, Anti-D, Childbearing age, Women, Cameroon

We conducted a cross sectional retrospective study to determine anti-D and D-negative phenotype rates among Cameroonian women of reproductive age (15 – 44 years), in order to evaluate the importance ofD alloimmunization. Analysis of the haematology laboratory records from January 2006 to December 2007 harvested 225 results for red blood cell alloantibody screening and 2460 D phenotypes. Anti-D rate was found to be high at 4% and not linked to women’s parity. Three hundred and fifty two (14.3%) women were found to be D-negative. Anti-D rates significantly decreased with age from 18.8% among teenagers (15-19) to 7.8% among older women (35-44) (p = 0.001). The number of women submitted to both irregular antibody screening and type D phenotype determination was not strong enough (50) to analyse the link between anti-D rate and antigen D distribution in our study (Afr J Reprod Health 2009; 13[3]:47-52)

Публицистика Джафера Сейдамета в период эмиграции (1918-1960 гг.)

Background: Parasite switches to new host species are of fundamental scientific interest and may be considered an important speciation mechanism. For numerous monogenean fish parasites, infecting different hosts is associated with morphological adaptations, in particular of the attachment organ (haptor). However, haptoral morphology in Cichlidogyrus spp. (Monogenea, Dactylogyridea), parasites of African cichlids, has been mainly linked to phylogenetic rather than to host constraints. Here we determined the position of Cichlidogyrus amieti, a parasite of species of Aphyosemion (Cyprinodontiformes, Nothobranchiidae) in the phylogeny of its congeners in order to infer its origin and assess the morphological changes associated with host-switching events. Methods: The DNA of specimens of C. amieti isolated from Aphyosemion cameronense in Cameroon was sequenced and analyzed together with that of Cichlidogyrus spp. from cichlid hosts. In order to highlight the influence of the lateral transfer of C. amieti on the haptoral sclerotised parts we performed a Principal Component Analysis (PCA) to compare the attachment organ structure of C. amieti to that of congeners infecting cichlids. Results: Cichlidogyrus amieti was found to be nested within a strongly supported clade of species described from Hemichromis spp. (i.e. C. longicirrus and C. dracolemma). This clade is located at a derived position of the tree, suggesting that C. amieti transferred from cichlids to Cyprinodontiformes and not inversely. The morphological similarity between features of their copulatory organs suggested that C. amieti shares a recent ancestor with C. dracolemma. It also indicates that in this case, these organs do not seem subjected to strong divergent selection pressure. On the other hand, there are substantial differences in haptoral morphology between C. amieti and all of its closely related congeners described from Hemichromis spp.. Conclusions: Our study provides new evidence supporting the hypothesis of the adaptive nature of haptor morphology. It demonstrates this adaptive component for the first time within Cichlidogyrus, the attachment organs of which were usually considered to be mainly phylogenetically constrained