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

An Overlooked Mandibular-Rubbing Behavior Used during Recruitment by the African Weaver Ant, Oecophylla longinoda

In Oecophylla, an ant genus comprising two territorially dominant arboreal species, workers are known to (1) use anal spots to mark their territories, (2) drag their gaster along the substrate to deposit short-range recruitment trails, and (3) drag the extruded rectal gland along the substrate to deposit the trails used in long-range recruitment. Here we study an overlooked but important marking behavior in which O. longinoda workers first rub the underside of their mandibles onto the substrate, and then—in a surprising posture—tilt their head and also rub the upper side of their mandibles. We demonstrate that this behavior is used to recruit nestmates. Its frequency varies with the rate at which a new territory, a sugary food source, a prey item, or an alien ant are discovered. Microscopy analyses showed that both the upper side and the underside of the mandibles possess pores linked to secretory glands. So, by rubbing their mandibles onto the substrate, the workers probably spread a secretion from these glands that is involved in nestmate recruitment

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

A temporary social parasite of tropical plant-ants improves the fitness of a myrmecophyte

Myrmecophytes offer plant-ants a nesting place in exchange for protection from their enemies, particularly defoliators. These obligate ant-plant mutualisms are common model systems for studying factors that allow horizontally transmitted mutualisms to persist since parasites of ant-myrmecophyte mutualisms exploit the rewards provided by host plants whilst providing no protection in return. In pioneer formations in French Guiana, Azteca alfari and Azteca ovaticeps are known to be mutualists of myrmecophytic Cecropia (Cecropia ants). Here, we show that Azteca andreae, whose colonies build carton nests on myrmecophytic Cecropia, is not a parasite of Azteca-Cecropia mutualisms nor is it a temporary social parasite of A. alfari; it is, however, a temporary social parasite of A. ovaticeps. Contrarily to the two mutualistic Azteca species that are only occasional predators feeding mostly on hemipteran honeydew and food bodies provided by the host trees, A. andreae workers, which also attend hemipterans, do not exploit the food bodies. Rather, they employ an effective hunting technique where the leaf margins are fringed with ambushing workers, waiting for insects to alight. As a result, the host trees' fitness is not affected as A. andreae colonies protect their foliage better than do mutualistic Azteca species resulting in greater fruit production. Yet, contrarily to mutualistic Azteca, when host tree development does not keep pace with colony growth, A. andreae workers forage on surrounding plants; the colonies can even move to a non-Cecropia tree

Predation success by a plant-ant indirectly favours the growth and fitness of its host myrmecophyte

Mutualisms, or interactions between species that lead to net fitness benefits for each species involved, are stable and ubiquitous in nature mostly due to "byproduct benefits" stemming from the intrinsic traits of one partner that generate an indirect and positive outcome for the other. Here we verify if myrmecotrophy (where plants obtain nutrients from the refuse of their associated ants) can explain the stability of the tripartite association between the myrmecophyte Hirtella physophora, the ant Allomerus decemarticulatus and an Ascomycota fungus. The plant shelters and provides the ants with extrafloral nectar. The ants protect the plant from herbivores and integrate the fungus into the construction of a trap that they use to capture prey; they also provide the fungus and their host plant with nutrients. During a 9-month field study, we over-provisioned experimental ant colonies with insects, enhancing colony fitness (i.e., more winged females were produced). The rate of partial castration of the host plant, previously demonstrated, was not influenced by the experiment. Experimental plants showed higher δ¹⁵N values (confirming myrmecotrophy), plus enhanced vegetative growth (e.g., more leaves produced increased the possibility of lodging ants in leaf pouches) and fitness (i.e., more fruits produced and more flowers that matured into fruit). This study highlights the importance of myrmecotrophy on host plant fitness and the stability of ant-myrmecophyte mutualisms

Journée de formation Polar

En lien avec le rectorat de Lyon, le réseau des bibliothèques municipales de Lyon et la DRAC Auvergne-Rhône-Alpes, cette journée a pour but de sensibiliser les enseignants et bibliothécaires au polar et de leur donner des pistes pour amorcer un travail sur le genre avec les adultes et les enfants. Le programme de cette journée s’articule autour d’interventions d’éditeurs, auteurs, libraires et autres professionnels du livre qui viendront notamment présenter des nouveautés polar 2018-2019, apporter des éclairages sur les raisons du succès du polar nordique et aborderont les spécificités du roman policier jeunesse

Panorama des nouveautés polar 2018-2019

Interventions de Jérôme Dejean (libraire) et Stanislas Rigot (librairie Lamartine- Paris 16e) dans le cadre de la journée de formation au polar

Panorama des parutions de polar 2017-2018 - Journée de formation au polar

Intervention de Stanislas Rigot, librairie Lamartine (Paris 16e) et Jérôme Dejean, Page des libraires dans le cadre de la journée de formation au Polar 2018

Dysplasie micro-nodulaire pigmentée des surrénales (de la clinique au diagnostic moléculaire chez six patients présentant un Complexe de Carney)

Le complexe de Carney (CC) est une néoplasie endocrinienne multiple pouvant être responsable d'un syndrome de Cushing ACTH-indépendant lié à une dysplasie nodulaire pigmentée de la corticosurrénale (PPNAD), de myxomes notamment cardiaques et d'une pigmentation cutanée en rapport avec une lentiginose et des naevi bleus. Récemment, des mutations germinales hétérozygotes inactivatrices de la sous-unité PKA-RIa de la Protéine Kinase A, enzyme cible de la voie de l'AMPc, ont été décrites dans le CC....Conclusion: La description de mutations germinales hétérozygotes de PKA-RIa dans le complexe de Carney nous permet à partir de cette situation particulière d'hyperplasie cortico-surrénalienne d'élaborer des hypothèses de travail pour une meilleure compréhension de la tumorigénèse surrénalienne.NANTES-BU Médecine pharmacie (441092101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF