Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
A major requirement for malaria elimination is the development of transmission-blocking interventions. In vitro transmission-blocking bioassays currently mostly rely on the use of very few Plasmodium falciparum reference laboratory strains isolated decades ago. To fill a piece of the gap between laboratory experimental models and natural systems, the purpose of this work was to determine if culture-adapted field isolates of P. falciparum are suitable for in vitro transmission-blocking bioassays targeting functional maturity of male gametocytes: exflagellation. Plasmodium falciparum isolates were adapted to in vitro culture before being used for in vitro gametocyte production. Maturation was assessed by microscopic observation of gametocyte morphology over time of culture and the functional viability of male gametocytes was assessed by microscopic counting of exflagellating gametocytes. Suitability for in vitro exflagellation-blocking bioassays was determined using dihydroartemisinin and methylene blue. In vitro gametocyte production was achieved using two isolates from French Guiana and two isolates from Cambodia. Functional maturity of male gametocytes was assessed by exflagellation observations and all four isolates could be used in exflagellation-blocking bioassays with adequate response to methylene blue and dihydroartemisinin. This work shows that in vitro culture-adapted P. falciparum field isolates of different genetic background, from South America and Southeast Asia, can successfully be used for bioassays targeting the male gametocyte to gamete transition, exflagellation.
ISSN: 1475-2875

Droits : http://creativecommons.org/licenses/by/
pasteur-01182753
https://hal-pasteur.archives-ouvertes.fr/pasteur-01182753
https://hal-pasteur.archives-ouvertes.fr/pasteur-01182753/document
https://hal-pasteur.archives-ouvertes.fr/pasteur-01182753/file/LeBas%20et%202015%20version%20publie%20%281%29.pdf
DOI : 10.1186/s12936-015-0752-x

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Myrmecophytism occurs in plants that offer ants a nesting space and, often, food rewards in exchange for protection from predators and competitors. Such biotic protection by ants can, however, interfere with the activity of pollinators leading to potential negative consequences for the plant’s reproduction. In this study, we focused on the association between the understory myrmecophyte, Hirtella physophora (Chrysobalanaceae), and its obligate ant partner, Allomerus decemarticulatus (Myrmicinae). We investigated the reproductive biology of H. physophora and the putative mechanisms that may limit ant–pollinator conflict. Our results show that H. physophora is an obligate outcrosser, self-incompatible, and potentially insect-pollinated species. The reproduction of H. physophora relies entirely on pollen transfer by pollinators that are likely quite specific. Potential interference between flower-visiting insects during pollination may also be lessened by a spatial and temporal segregation of ant and pollinator activities, thus enabling pollen transfer and fruit production.
ISSN: 1872-8855

hal-01140817
https://hal-sde.archives-ouvertes.fr/hal-01140817
DOI : 10.1007/s11829-014-9352-x

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : The diversity and functional identity of organisms are known to be relevant to the maintenance of ecosystem processes but can be variable in different environments. Particularly, it is uncertain whether ecosystem processes are driven by complementary effects or by dominant groups of species. We investigated how community structure (i.e., the diversity and relative abundance of biological entities) explains the community-level contribution of Neotropical ant communities to different ecosystem processes in different environments. Ants were attracted with food resources representing six ant-mediated ecosystem processes in four environments: ground and vegetation strata in cropland and forest habitats. The exploitation frequencies of the baits were used to calculate the taxonomic and trophic structures of ant communities and their contribution to ecosystem processes considered individually or in combination (i.e., multifunctionality). We then investigated whether community structure variables could predict ecosystem processes and whether such relationships were affected by the environment. We found that forests presented a greater biodiversity and trophic complementarity and lower dominance than croplands, but this did not affect ecosystem processes. In contrast, trophic complementarity was greater on the ground than on vegetation and was followed by greater resource exploitation levels. Although ant participation in ecosystem processes can be predicted by means of trophic-based indices, we found that variations in community structure and performance in ecosystem processes were best explained by environment. We conclude that determining the extent to which the dominance and complementarity of communities affect ecosystem processes in different environments requires a better understanding of resource availability to different species.
ISSN: 0029-8549

hal-01606497
https://hal.archives-ouvertes.fr/hal-01606497
DOI : 10.1007/s00442-016-3741-z
PRODINRA : 407457