L'activité de butinage des Apoides sauvages (Hymenoptera Apoidea) sur les fleurs de maïs à Yaounde (Cameroon) et réflexions sur la pollinisation des graminées tropicales

The gatering activity of wild bees (Hymenoptera Apoidea) on flowers of maize at Yaound (Cameroon) and further considerations on pollination of the tropical Gramineae. At Nkolbisson (Yaounde, Cameroon), in May 1991, flowers of maize (Zea mays L; Poaceae) were observed for the study of pollen gathering by five different species of wild bees: one Apidae Meliponinae (Dactylurina staudingeri) and four Halictidae Nomiinae (Lipotriches andrei, Lipotriches langi, Lipotriches notabilis and Leuconomia granulata). Each of these Apoidea is well attracted by pollen of maize. The larger number of bees foraging at the same time on a panicle varies from one with Dactylurina staudingeri to four with Lipotriches andrei and Lipotriches notabilis. Generally, bees forage maize during the whole day and during the full flowering period but visits are more numerous in the morning and during the period of intense flowering. Median duration of a visit on a male spikelet varies from 1 sec with Dactylurina staudingeri to 7 sec with Lipotriches andrei. These Apoidea have an elaborated behaviour when gathering pollen of maize. Dactylurina staudingeri however seems less adapted to the floral morphology of Poaceae comparing with Lipotriches. When foraging maize, all these bees are regular visitors to flowers of this plant, even in the presence of other flower species in the vicinity of the crop. Bees studied have a positive impact on the yield of grains due to a complementary action with the well known one of the wind. The influence is indirect as the bees are seldom visiting the stigmates. The explanation is that when the bees are very common on the panicles they shake the anthers, inducing the release of pollen grains in the atmosphere even in the days without wind. The part of wild bees in the increase of yields is estimated to 3/ while the one of the domestic bees (Apis mellifera) is estimated to 21/ in that locality. The authors are reviewing existing literature on grass crop pollination and on Poaceae in general by various species of bees. For a better integrated crop management of maize in Cameroon, it is suggested to conserve the nesting sites of Lipotriches in surrounding areas of crops and to avoid unjustified use of pesticides during the flowering period

Impact de l’activité de butinage de Apis mellifera adansonii Latreille (Hymenoptera : Apidae) sur la pollinisation et la chute des jeunes fruits du karité Vitellaria paradoxa (Sapotaceae) à Ngaoundéré (Cameroun)

Afin d’estimer la valeur apicole et d’évaluer l’impact de Apis mellifera adansonii sur le rendement fruitier de Vitellaria paradoxa Gaertner (Sapotaceae) au Cameroun, les activités de butinage, l’indice de fructification et le taux de chute des fruits avant maturité ont été enregistrés dans la savane de Tchabal-Bambi et de Béka (région de l’Adamaoua – Ngaoundéré). De décembre à janvier, en 2005/2006 et 2006/2007 respectivement, 120 et 200 inflorescences divisées en deux lots selon la présence ou l’absence de protection de ces inflorescences vis-à-vis des insectes ont été déterminées. Chaque année, les butineuses ont récolté le nectar et le pollen de façon intense et permanente. Le rythme des visites de A. m. adansonii a été positivement corrélé au rythme d’épanouissement des fleurs de V. paradoxa. Les données obtenues indiquent que la sapotacée est une plante apicole très fortement nectarifère et fortement pollinifère. L’indice de fructification des inflorescences non protégées a été significativement supérieur à celui des inflorescences protégées des insectes. La contribution numérique de A. m. adansonii dans la fructification a été de 57,74% en 2005/2006 et 53,55% en 2006/2007. La contribution numérique de A. m. adansonii dans la réduction du taux de chute des jeunes fruits a été de 19,04% en 2005/2006 et 52,21% en 2006/2007. L’installation des colonies de A. m. adansonii à proximité des populations de V. paradoxa est recommandée pour accroître son rendement en fruits et augmenter la production du miel.Keywords: Vitellaria paradoxa, Apis mellifera adansonii , butinage, pollinisation, fructificatio

Le paludisme urbain à Yaoundé, Cameroun : 1. Etude entomologique dans deux quartiers centraux

Une étude entomologique longitudinale sur les moustiques agressifs pour l'homme et la transmission du paludisme a été réalisée dans deux quartiers centraux de la ville de Yaoundé (Cameroun) d'avril 1989 à mars 1990. Le quartier Essos borde un bas-fond marécageux. Le quartier Obili est comparable à Essos, mais il y a beaucoup de bassins de pisciculture mal entretenus et couverts de végétation aquatique. Les moustiques furent échantillonnés de nuit, dans les maisons, sur appât humain, deux fois par mois dans chaque quartier. A Essos, un habitant reçoit annuellement près de 4000 piqûres de moustiques. Quatre espèces de moustiques sont capturées : #Culex #quinquefasciatus (84%), #Mansonia$(9$ #gambiae$(6$. #Funestus$(1$. #gambiae$est de 78$. #Funestus est absent et la proportion d'#A. #gambiae$est très basse (1$. #gambiae$, sur 11 dissections, sont pares. Aucune glande salivaire sur 16 dissections n'a été trouvée positive; cependant, l'indice sporozoïtique peut être estimé à 4$ (49% de la faune culicidienne agressive) est liée à l'abondance de la végétation aquatique due au manque d'entretien des bassins. (Résumé d'auteur

Foraging behaviour of Apis mellifera adansonii and its impact on pollination, fruit and seed yields of Citrullus lanatus at Nkolbisson (Yaoundé, Cameroon)

Honeybee (Apis mellifera adansonii Latreille (Hymenoptera: Apidae)) foraging activity was observed to evaluate its impact on pollination, fruit and seed yields of Citrullus lanatus (Thunb) Mansf (Cucurbitaceae) in the area of Yaoundé (Cameroon). Two lots of 775 female flowers were marked according to the presence or the absence of a protection for insect visits. The honey bees’ activity, the fruit set, the number of seeds per fruit were recorded. A. m. adansonii primarily foraged for nectar on C. lanatus throughout the whole blooming period of each plant and pollen collection was low. The mean maximum number of workers foraging at the same time was 331 ± 173 (n= 41) per 1000 flowers. The mean foraging speed was 10.20 ± 2.75 (n = 154) flowers per minute. The fruit set and the number of seeds per fruit of unprotected female flowers were significantly higher than those of female flowers protected from insects. A. m. adansonii pollination contributed 70.14% to the fruit set and seed yields. The conservation of A. m. adansonii colonies near C. lanatus population must be encouraged.Key words: Citrullus lanatus, Apis mellifera adansonii, pollination, yields, Cameroon.L’activité de butinage d’Apis mellifera adansonii Latreille (Hymenoptera : Apidae) a été étudiée afin d’évaluer son impact sur la pollinisation, les rendements fruitiers et grainiers de Citrullus lanatus (Thunb) Mansf (Cucurbitaceae) à Yaoundé (Cameroun). Deux lots ont été déterminés par le marquage de 775 fleurs femelles différant selon la présence ou l’absence de protection vis-à-vis des visites d’insectes. Le rythme saisonnier d’activité des abeilles domestiques, le taux de fructification des fleurs femelles et le nombre de graines par fruit ont été évalués. A. m. adansonii butinait les fleurs de C. lanatus tout au long de la période de floraison de chaque plante. Les butineuses prélevaient intensément le nectar pendant que la collecte du pollen était réduite. Le plus grand nombre d’ouvrières butinant simultanément était de 331 ± 173 (n = 41)par 1000 fleurs. La vitesse moyenne de butinage était de 10.20 ± 2.75 (n = 154) fleurs par minute. Le taux de fructification et le nombre moyen de graines matures par fruit des fleurs non protégées de l’activité des insectes étaient significativement élevés que ceux des fleurs femelles protégées. La contribution d’A. m. adansonii sur les rendements fruitiers et grainiers de C. lanatus était de 70.14% grâce à l’action pollinisatrice des ouvrières. La conservation des colonies d’A. m. adansonii à côté des populations de C. lanatus en fleurs doit être encouragée.Mots clés: Citrullus lanatus, Apis mellifera adansonii, pollinisation, rendements, Camerou

Inhibition of Fungi and Gram-Negative Bacteria by Bacteriocin BacTN635 Produced by Lactobacillus plantarum sp. TN635

The aim of this study was to evaluate 54 lactic acid bacteria (LAB) strains isolated from meat, fermented vegetables and dairy products for their capacity to produce antimicrobial activities against several bacteria and fungi. The strain designed TN635 has been selected for advanced studies. The supernatant culture of this strain inhibits the growth of all tested pathogenic including the four Gram-negative bacteria (Salmonella enterica ATCC43972, Pseudomonas aeruginosa ATCC 49189, Hafnia sp. and Serratia sp.) and the pathogenic fungus Candida tropicalis R2 CIP203. Based on the nucleotide sequence of the 16S rRNA gene of the strain TN635 (1,540 pb accession no FN252881) and the phylogenetic analysis, we propose the assignment of our new isolate bacterium as Lactobacillus plantarum sp. TN635 strain. Its antimicrobial compound was determined as a proteinaceous substance, stable to heat and to treatment with surfactants and organic solvents. Highest antimicrobial activity was found between pH 3 and 11 with an optimum at pH = 7. The BacTN635 was purified to homogeneity by a four-step protocol involving ammonium sulfate precipitation, centrifugal microconcentrators with a 10-kDa membrane cutoff, gel filtration Sephadex G-25, and C18 reverse-phase HPLC. SDS-PAGE analysis of the purified BacTN635, revealed a single band with an estimated molecular mass of approximately 4 kDa. The maximum bacteriocin production (5,000 AU/ml) was recorded after a 16-h incubation in Man, Rogosa, and Sharpe (MRS) medium at 30 °C. The mode of action of the partial purified BacTN635 was identified as bactericidal against Listeria ivanovii BUG 496 and as fungistatic against C. tropicalis R2 CIP203

A new limit on the light speed isotropy from the GRAAL experiment at the ESRF

When the electrons stored in the ring of the European Synchrotron Radiation Facility (ESRF, Grenoble) scatter on a laser beam (Compton scattering in flight) the lower energy of the scattered electron spectra, the Compton Edge (CE), is given by the two body photon-electron relativistic kinematics and depends on the velocity of light. A precision measurement of the position of this CE as a function of the daily variations of the direction of the electron beam in an absolute reference frame provides a one-way test of Relativistic Kinematics and the isotropy of the velocity of light. The results of GRAAL-ESRF measurements improve the previously existing one-way limits, thus showing the efficiency of this method and the interest of further studies in this direction.Comment: Proceed. MG12 meeting, Paris, July, 200

The {\eta}'-carbon potential at low meson momenta

The production of $\eta^\prime$ mesons in coincidence with forward-going protons has been studied in photon-induced reactions on $^{12}$C and on a liquid hydrogen (LH$_2$) target for incoming photon energies of 1.3-2.6 GeV at the electron accelerator ELSA. The $\eta^\prime$ mesons have been identified via the $\eta^\prime\rightarrow \pi^0 \pi^0\eta \rightarrow 6 \gamma$ decay registered with the CBELSA/TAPS detector system. Coincident protons have been identified in the MiniTAPS BaF$_2$ array at polar angles of $2^{\circ} \le \theta _{p} \le 11^{\circ}$. Under these kinematic constraints the $\eta^\prime$ mesons are produced with relatively low kinetic energy ($\approx$ 150 MeV) since the coincident protons take over most of the momentum of the incident-photon beam. For the C-target this allows the determination of the real part of the $\eta^\prime$-carbon potential at low meson momenta by comparing with collision model calculations of the $\eta^\prime$ kinetic energy distribution and excitation function. Fitting the latter data for $\eta^\prime$ mesons going backwards in the center-of-mass system yields a potential depth of V = $-$(44 $\pm$ 16(stat)$\pm$15(syst)) MeV, consistent with earlier determinations of the potential depth in inclusive measurements for average $\eta^\prime$ momenta of $\approx$ 1.1 GeV/$c$. Within the experimental uncertainties, there is no indication of a momentum dependence of the $\eta^\prime$-carbon potential. The LH$_2$ data, taken as a reference to check the data analysis and the model calculations, provide differential and integral cross sections in good agreement with previous results for $\eta^\prime$ photoproduction off the free proton.Comment: 9 pages, 13 figures. arXiv admin note: text overlap with arXiv:1608.0607

Limits on light-speed anisotropies from Compton scattering of high-energy electrons

The possibility of anisotropies in the speed of light relative to the limiting speed of electrons is considered. The absence of sidereal variations in the energy of Compton-edge photons at the ESRF's GRAAL facility constrains such anisotropies representing the first non-threshold collision-kinematics study of Lorentz violation. When interpreted within the minimal Standard-Model Extension, this result yields the two-sided limit of 1.6 x 10^{-14} at 95% confidence level on a combination of the parity-violating photon and electron coefficients kappa_{o+} and c. This new constraint provides an improvement over previous bounds by one order of magnitude.Comment: 4 pages, 4 figure

The effect of burnout in seniority in the workplace: mediation analysis of anxiety

Cada vez en mayor medida se hace patente que el síndrome de burnout es una realidad social. Esta disfunción psicológica está relacionada directamente con el ámbito laboral, que afecta especialmente a la profesión sanitaria, caracterizada por una continua relación de ayuda indispensable hacia otras personas, que a su vez dependen del citado personal. La muestra de estudio es de 70 trabajadores de un mismo centro del sector sanitario de atención de mayores de la ciudad de Granada. Los resultados muestran que la ansiedad se relacionará positivamente tanto con el burnout como con la antigüedad en el puesto, mientras que predecimos que a menor realización personal en presencia de mayor antigüedad los valores en ansiedad también serán más altos. También se comprueba que la ansiedad estado tiene efectos mediadores sobre la realización personal, puesto que puede causar mayor alteración de este estado que la propia antigüedad.As time goes by it becomes more and more evident that burnout syndrome is a social reality. This psychological dysfunction is directly related to the spheres of labour, especially affecting the sanitary profession, characterized by a continuous relationship of indispensable help towards others, who are dependent on them. The study sample comprised 70 workers of the same healthcare center focusing on elderly care in Granada. The results show that anxiety will correlate positively with burnout as well as with seniority at the job, while we predict anxiety levels will also be higher if there is low personal fulfilment in the presence of more job seniority. It is also proved that a state of anxiety has a mediating effect on personal fulfilment since it can cause a greater alteration in this state than job seniority.Departamento de Psicología Socia