When Choice Makes Sense: Menthol Influence on Mating, Oviposition and Fecundity in Drosophila melanogaster

International audienceThe environment to which insects have been exposed as larvae and adults can affect subsequent behaviors, such as mating, oviposition, food preference or fitness. Experience can change female preference for oviposition, particularly in phytophagous insects. In Drosophila melanogaster, females avoid laying eggs on menthol rich-food when given the choice. Exposure to menthol during larval development reduces this aversion. However, this observation was not reproduced in the following generation. Recently, we have shown that oviposition-site preference (OSP) differs between wild type D. melanogaster lines freely or forcibly exposed to menthol. After 12 generations, menthol "forced" lines still exhibit a persistent aversion to menthol whereas 'free-choice' lines show a decreased aversion for menthol rich-food. Here, we compare courtship behavior, mating and female fecundity in "forced" and "free-choice" lines, raised either on menthol rich-food (Menthol-lines) or on menthol-free food (Plain-lines). "Forced" males did not discriminate between decapitated virgin females of the two lines. They courted and mated with intact females of both "forced" lines in a comparable rate. However "forced" M-line males did mate significantly more rapidly with "forced" M-line females. In the "free-choice" procedure, P-line males show a similar pattern as "forced" males for discrimination ability and courtship. M-line males courted significantly more M-line females. Both 'free-choice' lines males mated significantly more with females of their own line. Female fecundity was assessed during 10 days in 'free-choice' lines. Menthol line females laid more eggs during the first 4 days than female Plain-lines and parental control-line. The total number of eggs laid during the first 10 days of female adult life is comparable in M-line and parental control line. However, Menthol-line females laid eggs earlier than both parental control and Plain-lines. Our findings show that in D. melanogaster, as for OSP, mating and fecundity are more rapidly influenced when flies have a choice between alternative resources compared to flies permanently exposed to menthol

Choice alters Drosophila oviposition site preference on menthol

Food choice and preference relies on multiple sensory systems that are under the control of genes and sensory experience. Exposure to specific nutrients and nutrient-related molecules can change food preference in vertebrates and invertebrates. For example, larval exposure of several holometabolous insects to menthol can change their adult response to this molecule. However, studies involving Drosophila melanogaster exposure to menthol produced controversial results due maybe to methodological differences. Here, we compared the ovipositionsite preference of wild-type D. melanogaster lines freely or forcibly exposed to menthol-rich food. After 12 generations, oviposition-site preference diverged between the two lines. Counterintuitively, menthol 'forced' lines showed a persistent aversion to menthol whereas 'free choice' lines exhibited a decreased aversion to menthol-rich food. This effect was specific to menthol since the 'free choice' lines showed unaltered responses to caffeine and sucrose. This suggests that the genetic factors underlying Drosophila oviposition site preference are more rapidly influenced when flies have a choice between alternative sources compared to flies permanently exposed to the same aversive substance. (C) 2013. Published by The Company of Biologists Ltd

Burkina Faso : revue du sous-secteur de l'enseignement agricole

National audienceLe dispositif national public est composé de l'Institut de développement rural de l'Université de Ouagadougou (IDR), de trois écoles formant des techniciens moyens et supérieurs spécialisés (agriculture, zootechnie, forêt), et d'un "système de formation des jeunes agriculteurs" (SFJA) comprenant 406 centres FJA, 5 centres de promotion rurale, et 2 centres de formation de formateurs de niveau supérieur (CFFA). Cet ensemble mobilisait en 1991/92 d'importantes ressources (770 enseignants, en quasi totalité nationaux, et 2,15 milliards de FCFA, dont 1,5 d'origine nationale équivalant à près de 0,6% du produit intérieur brut agricole) ; mais il est caractérisé par la faiblesse des relations entre les institutions citées et par la place mal définie du SFJA à côté des programmes nationaux d'alphabétisation et de vulgarisation agricole, et des activités de formation des nombreux projets de développement. Le Burkina Faso héberge par ailleurs quatre écoles régionales de formation de cadres supérieurs et moyens agricoles (équipement rural, hydraulique, télédétection, économie) ouvertes aux pays sahéliens et africains, qui disposent de moyens relativement considérables (74 enseignants ; budget total de 1,35 milliard de FCFA)

Les strategies de selection pour l'amelioration des cereales

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Submersible Dielectric Probe for In Situ Monitoring of Suspensions and Its Application to Activated Sludge in Waste Water Treatment Plant

International audienceWe have developed a useful dielectric probe that allows real-time and in situ characterization of suspensions in the 0.4 to 10 MHz frequency range. It has been successfully tested throughout several weeks to monitor activated sludge of a waste water treatment plant. In this paper the results are compared with those obtained in parallel using both static or flow classic dielectric cells

Preconcentration Electroanalysis at Surfactant-Templated Thiol-Functionalized Silica Thin Films

International audienceSurfactant‐templated thiol‐functionalized silica thin films have been deposited by spin‐coating on glassy carbon electrodes. Their permeability properties have been characterized using three solution phase redox probes (Ru(NH3)equation image, Fe(CN)equation image, FcMeOH) and their suitability to be applied for preconcentration electroanalysis has been studied using Ag+ as model analyte. Both the film permeability to redox probes and the performance of the modified electrodes towards Ag+ sensing were found to be dramatically influenced by the composition of the sol used for preparing the thin films, and especially its surfactant content. The best results were obtained with materials prepared from rather high surfactant concentration because they led (after template removal) to highly open mesoporous deposits with readily accessible thiol groups in the mesopore channels. The effect of various parameters on the electrode response have been investigated, including the composition of the detection medium, the accumulation time, the level of functionalization of the films and their preparation conditions, and the analyte concentration. A linear response for Ag+ was obtained in the 0.2–10 μM concentration range

Drosophila adult and larval pheromones modulate larval food choice

Insects use chemosensory cues to feed and mate. In Drosophila, the effect of pheromones has been extensively investigated in adults, but rarely in larvae. The colonization of natural food sources by Drosophila buzzatii and Drosophila simulans species may depend on species-specific chemical cues left in the food by larvae and adults. We identified such chemicals in both species and measured their influence on larval food preference and puparation behaviour. We also tested compounds that varied between these species: (i) two larval volatile compounds: hydroxy-3-butanone-2 and phenol (predominant in D. simulans and D. buzzatii, respectively), and (ii) adult cuticular hydrocarbons (CHs). Drosophila buzzatii larvae were rapidly attracted to non-CH adult conspecific cues, whereas D. simulans larvae were strongly repulsed by CHs of the two species and also by phenol. Larval cues from both species generally reduced larval attraction and pupariation on food, which was generally-but not always-low, and rarely reflected larval response. As these larval and adult pheromones specifically influence larval food search and the choice of a pupariation site, they may greatly affect the dispersion and survival of Drosophila species in nature

Drosophila Food-Associated Pheromones: Effect of Experience, Genotype and Antibiotics on Larval Behavior

International audienceAnimals ubiquitously use chemical signals to communicate many aspects of their social life. These chemical signals often consist of environmental cues mixed with species-specific signals-pheromones-emitted by conspecifics. During their life, insects can use pheromones to aggregate, disperse, choose a mate, or find the most suitable food source on which to lay eggs. Before pupariation, larvae of several Drosophila species migrate to food sources depending on their composition and the presence of pheromones. Some pheromones derive from microbiota gut activity and these food-associated cues can enhance larval attraction or repulsion. To explore the mechanisms underlying the preference (attraction/repulsion) to these cues and clarify their effect, we manipulated factors potentially involved in larval response. In particular, we found that the (i) early exposure to conspecifics, (ii) genotype, and (iii) antibiotic treatment changed D. melanogaster larval behavior. Generally, larvae-tested either individually or in groups-strongly avoided food processed by other larvae. Compared to previous reports on larval attractive pheromones, our data suggest that such attractive effects are largely masked by food-associated compounds eliciting larval aversion. The antagonistic effect of attractive vs. aversive compounds could modulate larval choice of a pupariation site and impact the dispersion of individuals in nature

Aging-related variation of cuticular hydrocarbons in wild type and variant drosophila melanogaster

International audienceThe cuticle of all insects is covered with hydrocarbons which have multiple functions. Cuticular hydrocarbons (CHCs) basically serve to protect insects against environmental harm and reduce dehydration. In many species, some CHCs also act as pheromones. CHCs have been intensively studied in Drosophila species and more especially in D. melanogaster. In this species, flies produce about 40 CHCs forming a complex sex- and species-specific bouquet. The quantitative and qualitative pattern of the CHC bouquet was characterized during the first days of adult life but remains unexplored in aging flies. Here, we characterized CHCs during the whole-or a large period of-adult life in males and females of several wild type and transgenic lines. Both types of lines included standard and variant CHC profiles. Some of the genotypes tested here showed very dramatic and unexpected aging-related variation based on their early days' profile. This study provides a concrete dataset to better understand the mechanisms underlying the establishment and maintenance of CHCs on the fly cuticle. It could be useful to determine physiological parameters, including age and response to climate variation, in insects collected in the wild

Desiccation resistance: effect of cuticular hydrocarbons and water content in Drosophila melanogaster adults

International audienceBackground: The insect cuticle covers the whole body and all appendages and has bi-directionnal selective permeability: it protects against environmental stress and pathogen infection and also helps to reduce water loss. The adult cuticle is often associated with a superficial layer of fatty acid-derived molecules such as waxes and long chain hydrocarbons that prevent rapid dehydration. The waterproofing properties of cuticular hydrocarbons (CHs) depend on their chain length and desaturation number. Drosophila CH biosynthesis involves an enzymatic pathway including several elongase and desaturase enzymes. Methods: The link between desiccation resistance and CH profile remains unclear, so we tested (1) experimentally selected desiccation-resistant lines, (2) transgenic flies with altered desaturase expression and (3) natural and laboratory-induced CH variants. We also explored the possible relationship between desiccation resistance, relative water content and fecundity in females. Results: We found that increased desiccation resistance is linked with the increased proportion of desaturated CHs, but not with their total amount. Experimentally-induced desiccation resistance and CH variation both remained stable after many generations without selection. Conversely, flies with a higher water content and a lower proportion of desaturated CHs showed reduced desiccation resistance. This was also the case in flies with defective desaturase expression in the fat body. Discussion: We conclude that rapidly acquired desiccation resistance, depending on both CH profile and water content, can remain stable without selection in a humid environment. These three phenotypes, which might be expected to show a simple relationship, turn out to have complex physiological and genetic links