Arboreal ants use the "Velcro® principle" to capture very large prey

Plant-ants live in a mutualistic association with host plants known as "myrmecophytes" that provide them with a nesting place and sometimes with extra-floral nectar (EFN) and/or food bodies (FBs); the ants can also attend sap-sucking Hemiptera for their honeydew. In return, plant-ants, like most other arboreal ants, protect their host plants from defoliators. To satisfy their nitrogen requirements, however, some have optimized their ability to capture prey in the restricted environment represented by the crowns of trees by using elaborate hunting techniques. In this study, we investigated the predatory behavior of the ant Azteca andreae which is associated with the myrmecophyte Cecropia obtusa. We noted that up to 8350 ant workers per tree hide side-by-side beneath the leaf margins of their host plant with their mandibles open, waiting for insects to alight. The latter are immediately seized by their extremities, and then spread-eagled; nestmates are recruited to help stretch, carve up and transport prey. This group ambush hunting technique is particularly effective when the underside of the leaves is downy, as is the case for C. obtusa. In this case, the hook-shaped claws of the A. andreae workers and the velvet-like structure of the underside of the leaves combine to act like natural VelcroH that is reinforced by the group ambush strategy of the workers, allowing them to capture prey of up to 13,350 times the mean weight of a single worker

Ants mediate the structure of phytotelm communities in an ant-garden bromeliad

The main theories explaining the biological diversity of rain forests often confer a limited understanding of the contribution of interspecific interactions to the observed patterns. We show how two-species mutualisms can affect much larger segments of the invertebrate community in tropical rain forests. Aechmea mertensii (Bromeliaceae) is both a phytotelm (plant-held water) and an ant-garden epiphyte. We studied the influence of its associated ant species (Pachycondyla goeldii and Camponotus femoratus) on the physical characteristics of the plants, and, subsequently, on the diversity of the invertebrate communities that inhabit their tanks. As dispersal agents for the bromeliads, P. goeldii and C. femoratus influence the shape and size of the bromeliad by determining the location of the seedling, from exposed to partially shaded areas. By coexisting on a local scale, the two ant species generate a gradient of habitat conditions in terms of available resources (space and food) for aquatic invertebrates, the diversity of the invertebrate communities increasing with greater volumes of water and fine detritus. Two-species mutualisms are widespread in nature, but their influence on the diversity of entire communities remains largely unexplored. Because macroinvertebrates constitute an important part of animal production in all ecosystem types, further investigations should address the functional implications of such indirect effects

Lutte contre les salissures marines : approche par procédés enzymatiques

L'adhésion de salissures marines sur les structures immergées en eau de mer cause de sévères dégâts et problèmes économiques par une accélération de la dégradation des matériaux et une diminution des performances industrielles. Nous avons choisi de tester le potentiel antisalissure de préparations enzymatiques commerciales de type hydrolases (protéases, glycosidases et lipases) sur les premières étapes d'adhésion des salissures marines : le biofilm bactérien. Un test d'évaluation de propriétés antisalissures concernant l'adhésion d'une bactérie marine du genre Pseudoalteromonas sp. D41 en microplaque et en eau de mer naturelle stérile a été mis au point. Ce test est adapté au criblage d'activités de prévention ou de nettoyage d'un biofilm marin et permet de tester la toxicité des préparations enzymatiques sur les cellules non adhérées. Les taux d'inhibition exprimés en fonction du logarithme de la concentration en enzyme consiste en une courbe sigmoïde de type dose-réponse. Des hydrolases testées, les protéases dont la subtilisine sont les plus efficaces. Un mélange d'activités enzymatiques amylases, lipases et protéases a montré une forte synergie d'activité pour inhiber l'adhésion de Pseudoalteromonas sp. D41 en microplaque. L'étude de la composition de substances polymériques produites par Pseudoalteromonas sp. D41 en fermenteur et au sein d'un biofilm a permis de mieux comprendre la nature des molécules organiques cibles impliquées dans l'inhibition de l'adhésion.\ud ____________________________________________________________Fouling on marine underwater surfaces causes critical and economic problems such as important material biodamages and industrial performances reduction. We chose to test antifouling potential of enzymatic commercial preparations like hydrolases (proteases, glycosidases and lipases) in order to inhibit the first fouling adhesion step: bacterial biofilm formation. An evaluation test of antifouling properties onto marine bacterial adhesion was designed using a mono-incubation of Pseudoalteromonas sp. D41 in microtiter plate and in sterile natural sea water. This test was adapted to screen agents for bacterial adhesion removal or inhibition activities and allowed to test enzymatic preparations toxicity on non adhered bacteria. Inhibition rates according to logarithm of enzymatic preparation concentration exhibits a sigmoid shape like dose-response curves. Among hydrolases, proteases like subtilisin are the most efficient enzymes. The efficiency of amylase, lipase and protease activity mixture was evaluated and showed a high synergistic inhibition on Pseudoalteromonas sp. D41 adhesion in microtiter plate. Studies on polymeric extracellular substances from Pseudoalteromonas sp. D41 in fermentation and in biofilm will be helpful in the understanding of the organic molecules nature involved in the adhesion inhibition

CSR in Belgium: the institutional context and practices

Corporate Social Responsibility is a quite recent concept in Belgium which has gained significant momentum since 1995. In May 1997, Belgium set up a legal framework for sustainable development. In April 2006, the government adopted a Reference Framework for CSR followed in 2007 by the CSR action plan. Next to governmental initiatives, the number of actors and platforms involved in CSR has significantly increased leading to the multiplication of CSR initiatives. However, it would be overoptimistic to state that CSR is a well and equally established concept and a set of practices among all Belgian companies. Indeed, CSR in Belgium offers great disparities and diversities. Based on multiple sources of information, the paper provides a descriptive and narrative view on CSR in Belgium, gradually leading towards reflection by the end of the paper. After a brief overview of the context for corporate social responsibility in Belgium, the paper investigates the different components that have been shaping CSR since the 1970s. Subsequently it zooms in to the CSR practices in Belgian companies. Finally, conclusions are drawn on the progress made in Belgium in the area of corporate social responsibility and the future prospects

Des plantes tropicales qui forment des mares : les broméliacées-citerne : un écosystème aquatique miniature capital pour la biodiversité

Les plantes qui présentent des structures anatomiques permettant de retenir de l'eau en permanence sont assez répandues en milieu tropical. Si beaucoup sont maintenant cultivées pour être vendues en jardineries, faisant le bonheur des amateurs, elles forment en milieu naturel des écosystèmes aquatiques encore très peu étudiés et renferment une biodiversité que l'on est loin d'avoir recensée. En Amérique centrale et du Sud, les broméliacées-citerne, qui représentent les plus nombreuses et les plus diversifiées de ces "plantes-mares", permettent à des organismes très variés d'accomplir leur cycle de vie

Dynamics of the association between a long-lived understory myrmecophyte and its specific associated ants

Myrmecophytic symbioses are widespread in tropical ecosystems and their diversity makes them useful tools for understanding the origin and evolution of mutualisms. Obligate ant–plants, or myrmecophytes, provide a nesting place, and, often, food to a limited number of plant–ant species. In exchange, plant–ants protect their host plants from herbivores, competitors and pathogens, and can provide them with nutrients

Post-rift uplift of the Dhofar margin (Gulf of Aden)

International audienceAn investigation of the sedimentation pattern along the Dhofar margin allows us to describe its late-stage evolution. After the accumulation of a thick post-rift sedimentary succession, two debris flow events occurred at the foot of the slope. The first event, affecting a wide area of the margin, marks a major change in sedimentation. The second event is associated with a shift of sedimentary deposition from the slope toward the basin. This latter debris flow was caused by an uplift phase, and highlights two distinct deformational styles in the eastern and western part of the Dhofar margin. Both events occurred very late in the history of the margin, at least 7.6 Ma after the end of the rifting phase (35-17.6 Ma)

TRANSVAC workshop on standardisation and harmonisation of analytical platforms for HIV, TB and malaria vaccines: 'how can big data help?'.

High-throughput analyses of RNA and protein expression are increasingly used for better understanding of vaccine-induced immunity and protection against infectious disease. With an increasing number of vaccine candidates in clinical development, it is timely to consider standardisation and harmonisation of sample collection, storage and analysis to ensure results of highest quality from these precious samples. These challenges were discussed by a group of international experts during a workshop organised by TRANSVAC, a European Commission-funded Research Infrastructure project. The main conclusions were: Platforms are rarely standardised for use in preclinical and clinical studies. Coordinated efforts should continue to harmonise the experimental set up of these studies, as well as the establishment of internal standards and controls. This will ensure comparability, efficiency and feasibility of the global analyses performed on preclinical and clinical data sets