Abstract: The hunting behavior of the African ponerine ant Pachycondyla pachyderma, a semi-specialized centipede predator, appears well adapted to this kind of prey and shows a graded complexity according to the difficulty it has in overwhelming prey. Small prey (5-to-8-mm-long termites) were detected by contact and seized by the thorax while larger prey (>= 30-mm-long centipedes) were frequently detected from a distance and seized by the anterior-most part of their body. Termites and 30-mm-long lithobiomorph centipedes were not always stung, whereas stinging and even repeated stinging was needed for 50-mm-long geophilomorphs and scolopendromorphs. Moreover, overwhelming wide and heavy scolopendromorphs, which have better defensive abilities, involved the use of additional behaviors allowing the workers to capture them safely: venom spreading, and a peculiar stinging posture, the “fatal embrace”. Here the workers seize scolopendromorphs by an antenna or by one of their first legs, wrap themselves around the prey while maintaining their grip with their mandibles and legs, and slowly inject venom into the prey's ventral surface. Workers retrieve small prey solitarily while, for large geophilomorphs and scolopendromorphs, nestmates can be recruited at short range or even at long range through tandem running. (C) 2010 Elsevier B.V. All rights reserved.

Abstract: Abstract We experimentally studied the predatory behavior of Polybia rejecta (Vespidae, Polistinae, Epiponini) towards 2–88 mm-long insects attracted to a UV light trap. Foragers, which began to hunt at 6:30, selected 4–14 mm-long prey insects. Prey detection by sight by hovering wasps was confirmed using decoys. After the wasps landed and walked along a sinuous path, prey were detected by contact or from a distance (1–3 cm). This was followed by seizure, stinging (contrarily to most other known cases), prey manipulation and retrieval. Prey that flew off might be caught in flight. The prey load, representing 30.7% of a forager’s weight, was optimized by capturing up to six small prey or two medium-sized prey successively (both of which might be consumed in situ). The foragers cut off the wings of larger prey or cut them into two pieces and returned to gather the second piece. The handling time increased exponentially with the weight of the prey. Partial loading (i.e., retrieving a load much inferior to the maximum possible) was likely related to social facilitation, a form of nest-based recruitment that was demonstrated through the experimental elimination of local enhancement by removing foragers (both mechanisms favor the exploitation of favorable patches).

Abstract: In the face of increasing drug resistance, the development of new anthelmintics is critical for controlling nematodes that parasitise livestock. Although hymenopteran venom toxins have attracted attention for applications in agriculture and medicine, few studies have explored their potential as anthelmintics. Here we assessed hymenopteran venoms as a possible source of new anthelmintic compounds by screening a panel of ten hymenopteran venoms against Haemonchus contortus, a major pathogenic nematode of ruminants. Using bioassay-guided fractionation coupled with liquid chromatography-tandem mass spectrometry, we identified four novel anthelmintic peptides (ponericins) from the venom of the neotropical ant Neoponera commutata and the previously described ponericin M−PONTX−Na1b from Neoponera apicalis venom. These peptides inhibit H. contortus development with IC50 values of 2.8–5.6 μM. Circular dichroism spectropolarimetry indicated that the ponericins are unstructured in aqueous solution but adopt α-helical conformations in lipid mimetic environments. We show that the ponericins induce non-specific membrane perturbation, which confers broad-spectrum antimicrobial, insecticidal, cytotoxic, hemolytic, and algogenic activities, with activity across all assays typically correlated. We also show for the first time that ponericins induce spontaneous pain behaviour when injected in mice. We propose that the broad-spectrum activity of the ponericins enables them to play both a predatory and defensive role in neoponeran ants, consistent with their high abundance in venom. This study reveals a broader functionality for ponericins than previously assumed, and highlights both the opportunities and challenges in pursuing ant venom peptides as potential therapeutics.

Abstract: A closed depression is defined as a geomorphologic element where a sediment depository is encircled by hillslopes. Despite the fact that closed depressions are often the only stagnant water points in many European landscapes, few ecological researches on their plant assemblages have been done. The main goal of this study was to give first results of the environmental factors responsible for the vegetation composition, richness and rarity in the closed depressions of the Lorraine biogeographical district (Belgium, France and grand-duche de Luxembourg). We surveyed for plant presence 85 forest and 77 grassland closed depressions. For each site, wetland area, local environmental factors and regional connectivities registered. For each species, the Ellenberg values were compiled. To investigate the main source of variation in species composition and in species richness (including richness in rare species), Non-metric Multidimensional Scaling analyses and Generalized Linear Models were respectively used. Species pools in forest (forest and preforest species) and in grassland (bog plants, pioneers, helophytes) were quite different. In both landscapes, a gradient from plants typical of basic high-productive soils to plants typical of acid low-productive soils reflects a shared successional gradient. The accumulation of organic matter allowed the establishment of Sphagnum spp., which slowly acidified the soil and thus acted as ecosystem engineers for the arrival of bog plants. Moreover, the species composition was additionally driven by the plant light tolerance in forests and by the plant water requirements in grasslands. Mechanisms of species accumulation (increase in species richness) were different in forests and in grasslands: respectively related to the plant light tolerance and to the wetland area. At the regional level, the averaged soil productivity was negatively related to the richness in rare species. Indeed, perennial highly-competitive plants such as Glyceria spp., Iris pseudacorus or Urtica dioica impeded the establishment of smaller and rarer species. At the habitat level, isolated closed depressions (due to either low connectivity or low grazing pressure) have more habitat rare species, giving evidences of dispersal limitation in plant assemblages of closed depressions.

Abstract: Geomorphic landscape features have been suggested as indicators of forest diversity. However, their explanatory power has not yet been explicitly tested at a regional scale in tropical rainforest. We used forest inventories conducted according to a stratified sampling design (3,132 plots in 111 transects at 33 sites) and holistic multi-scale geomorphological mapping derived from a Shuttle Radar Topography Mission digital elevation model to describe and explain spatial patterns in floristic composition across French Guiana (80,000 km2). We measured and identified 123,906 trees with DBH ≥20 cm and used constrained and unconstrained ordinations to analyze variations in the abundance of 221 taxa and 51 families. Variance partitioning and variograms were used to detect spatial patterns in species composition, compare the explanatory power of spatial and environmental factors, and select the variables that best explain forest composition. Strong floristic patterns corresponded to a major latitudinal gradient and significant sub-regional floristic structure. Geomorphological landscapes shaped by historic climate fluctuations and major geological events successfully captured these patterns and explained the variation in abundance of 80 taxa, corresponding to 65 % of the inventoried trees. Our findings suggest that long-term forest dynamics are under substantial “geomorphographic control”. A geomorphological perspective on landscapes that incorporates current and past environmental filters and historical biogeographical processes could thus be used more systematically in tropical regions for regional planning and forest conservation. © 2014, Springer Science+Business Media Dordrecht.