Diversité Taxonomique Des Hémiptères Aquatiques De La Ville De Daloa (Centre-Ouest, Côte d’Ivoire): Caractérisation Spécifique et Clé de Détermination des Familles

Les Hémiptères aquatiques constituent un groupe de macro-invertébrés très diversifié possédant des sensibilités diverses aux variations spécifiques de l’environnement induites par la pollution ou la modification de l’habitat. La diversité taxonomique des Hémiptères aquatiques a été étudiée dans les plans d’eau urbains de Daloa à partir d’un échantillonnage à la benne et au filet troubleau sur 12 stations au cours de deux saisons hydrologiques. Au total,  21 taxons appartenant à 10 familles regroupées en deux infra-ordres Gerromorpha et  Nepomorpha ont été identifiés. Les Nepomorpha comptent 12 taxons appartenant à 6 familles dont les Belostomatidae et les Corixidae renfermant le plus grand nombre de taxons.  Quant au Gerromorpha, ce sont 9 taxons répartis en 4 familles dont les plus importantes sont les Gerridae et les Veliidae. Une clé d’identification des familles des Hémiptères aquatiques a été établie. Des descriptions sommaires des espèces ont été faites pour faciliter leur identification

Theoretical Studies of the Chemical Reactivity of a Series of Coumarin Derivatives by the Density Functional Theory

The global descriptors of reactivity such as HOMO and LUMO energies, chemical hardness, electrophilicity, softness and dipole moment are theoretically determined for five coumarin derivatives in this paper. The analysis of the determined descriptors allows us to classify the studied molecules according to their reactivities. Thus, compound M3 is qualified to be the most reactive and the least stable with 3.933 eV as its gap energy ΔEgap. It is at the same time the softest, the best electron donor, the most electrophilic and the most polar molecule. The study of thermodynamic parameters shows that all the reactions of formation of studied coumarin derivatives are exothermic and spontaneous with less disorder. Furthermore, Hirschfield population analysis was carried out in order to locate the reactive sites, that are assumed to be the electrophilic and nucleophilic sites of the molecules. It appears that all the reactive sites are located on carbon atoms except those of molecule M3 which are located on oxygen atoms. Compounds M1 and M2 have the same electrophilic site (C15) and the same nucleophilic site (C13) thereby showing that the methyl group does not have any influence on the reactive site. The electrophilic site of the molecule M3 is located on both the identical oxygen atoms O33 and O34 while its nucleophilic site is located on the oxygen atoms O12. The electrophilic sites of compound M4 and M5 are the same and it is located on carbon atom(C11) while the nucleophilic site is located on carbon atom C23 for molecule M4. Concerning the nucleophilic sites of molecule M5 it is located on carbon atom C20. The difference nucleophilic reactive site may be due to the conjugation of activity of both fluorine atom and methyl group on the M5

Control of cassava mealybug Phenacoccus manihoti (Homoptera: Pseudococcidae) using NECO 50EC biopesticide in Grand Lahou (Côte d’Ivoire)

International audienceCassava (Manihot esculenta Crantz) is a food crop with tuberous roots that plays an important role in feeding populations. The need to control cassava pests led to testing the effect of the biopesticide NECO 50 EC on Phenacoccus manihoti in a plot of the city of Grand-Lahou. The effectiveness of the biopesticide NECO 50 EC was tested on larvae and adults of P. manihoti, in comparison with a conventional insecticide K-OPTIMAL 35 EC. Dilutions gave 5 respective concentrations of NECO 50 EC: 8.33 g/l; 4.54g/l; 3.12g/l; 2.38 g/l and 1.92 g/l, and a concentration of 0.093 g/l for the control insecticide. Spraying of cassava plants infested with mealybugs was undertaken and observations were made 24 hours, 48 hours and 72 hours after treatment. On the larvae, the highest rate (92.07 ± 0%) is obtained at a concentration of 8.33 g/l for NECO and 98.51% for the control insecticide. In adults for NECO the highest rate (62.50 ± 0%) is obtained at the concentration of 8.33 g/l and 96.17% for the control insecticide. The biopesticide NECO 50 EC could be used as an alternative to the excessive use of synthetic insecticides to reduce the damage of the pest P. manihoti

Molecular analysis of phosphate limitation in Geobacteraceae during the bioremediation of a uranium-contaminated aquifer

Nutrient limitation is an environmental stress that may reduce the effectiveness of bioremediation strategies, especially when the contaminants are organic compounds or when organic compounds are added to promote microbial activities such as metal reduction. Genes indicative of phosphate-limitation were identified by microarray analysis of chemostat cultures of Geobacter sulfureducens. This analysis revealed that genes in the pst-pho operon, which is associated with a high-affinity phosphate uptake system in other microorganisms, had significantly higher transcript abundance under phosphate-limiting conditions, with the genes pstB and phoU upregulated the most. Quantitative PCR analysis of pstB and phoU transcript levels in G. sulfurreducens grown in chemostats demonstrated that the expression of these genes increased when phosphate was removed from the culture medium. Transcripts of pstB and phoU within the subsurface Geobacter species predominating during an in situ uranium-bioremediation field experiment were more abundant than in chemostat cultures of G. sulfurreducens that were not limited for phosphate. Addition of phosphate to incubations of subsurface sediments did not stimulate dissimilatory metal reduction. The added phosphate was rapidly adsorbed onto the sediments. The results demonstrate that Geobacter species can effectively reduce U(VI) even when experiencing suboptimal phosphate concentrations and that increasing phosphate availability with phosphate additions is difficult to achieve because of the high reactivity of this compound. This transcript-based approach developed for diagnosing phosphate limitation should be applicable to assessing the potential need for additional phosphate in other bioremediation processes