Biosynthesis of the defensive alkaloid cicindeloine in Stenus solutus beetles

To protect themselves from predation and microorganismic infestation, rove beetles of the genus Stenus produce and store bioactive alkaloids like stenusine, 3-(2-methyl-1-butenyl)pyridine, and cicindeloine in their pygidial glands. The biosynthesis of stenusine and 3-(2-methyl-1-butenyl)pyridine was previously investigated in Stenus bimaculatus and Stenus similis, respectively. Both molecules follow the same biosynthetic pathway, where the N-heterocyclic ring is derived from l-lysine and the side chain from l-isoleucine. The different alkaloids are finally obtained by slight modifications of shared precursor molecules. The piperideine alkaloid cicindeloine occurs as a main compound additionally to (E)-3-(2-methyl-1-butenyl)pyridine and traces of stenusine in the pygidial gland secretion of Stenus cicindeloides and Stenus solutus. Feeding of S. solutus beetles with [D,¹⁵N]-labeled amino acids followed by GC/MS analysis techniques showed that cicindeloine is synthesized via the identical pathway and precursor molecules as the other two defensive alkaloids.     

Cold resistance depends on acclimation and behavioral caste in a temperate ant

Adjusting to low temperatures is important for animals living in cold environments. We studied the chill–coma recovery time in temperate ant workers (Temnothorax nylanderi) from colonies collected in autumn and spring in Germany. We experimentally acclimated these ant colonies to cold temperatures followed by warm temperatures. As expected, cold-acclimated workers recovered faster from freezing temperatures, but subsequent heat acclimation did not change the short recovery times observed after cold acclimation. Hence, either heat acclimation improves cold tolerance, possibly as a general response to stress, or at least it does not negate enhanced cold tolerance following cold acclimation. Colonies collected in spring showed similar cold tolerance levels to cold-acclimated colonies in the laboratory. Next, we compared the chill–coma recovery time of different worker castes and found that exterior workers recovered faster than interior workers. This difference may be related to their more frequent exposure to cold, higher activity level, or distinct physiology. Interior workers were also heavier and showed a higher gaster-to-head ratio and thorax ratio compared to exterior workers. An obvious difference between exterior and interior workers is activity level, but we found no link between activity and cold tolerance. This suggests that physiology rather than behavioral differences could cause the increased cold tolerance of exterior workers. Our study reveals the importance of acclimation for cold tolerance under natural and standardized conditions and demonstrates differences in cold tolerance and body dimensions in monomorphic behavioral castes of an ant.     

Greenhouse gas emissions from nitrogen fertilizer use in China

The use of synthetic nitrogen (N) fertilizers is an important driver of energy use and greenhouse gas (GHG) emissions in China. This paper develops a GHG emission factor for synthetic N fertilizer application in China. Using this emission factor, we estimate the scale of GHG emissions from synthetic nitrogen fertilizer use in Chinese agriculture and explore the potential for GHG emission reductions from efficiency improvements in N fertilizer production and use. The paper concludes with a discussion on costs and financing for a large-scale fertilizer efficiency improvement program in China, and how a GHG mitigation framework might contribute to program design.     

Movements and site fidelity of the giant manta ray, <Emphasis Type="Italic">Manta birostris,</Emphasis> in the Komodo Marine Park,Indonesia

Despite their large size and frequent occurrence in near-shore tropical habitats, little published information is available on the movements and behaviors of the giant manta ray, Manta birostris, and what factors influence visitation patterns. To examine the movements of manta rays in the Komodo Marine Park, Indonesia, an acoustic array was installed at up to seven sites in the park between 2000 and 2003. A total of 41 acoustic tags were deployed in three separate deployments in 2000, 2001 and 2002. Mantas were recorded in the park for up to 526 days with an average duration of 183 ± 136 days, when mantas made from 3 to 303 individual visits to different sites (median 58 visits). There was a clear preference for three sites that comprised over 90% of manta activity. The most popular site (German Flag) was off the southern tip of Komodo Island in an area with a high degree of bathymetric structure. Examination of the longest records suggests some site preference with 5 of 7 individuals spending greater than 90% of their time at the location where they were tagged. Using a general linear model it was possible to examine the effects of daytime, lunar phase, aggregation site, season and tidal phase on visitation patterns. The vast majority of visits were recorded during daylight hours at all sites. The strongest effects of both the lunar and tidal phase were apparent in the northern sites with the most visits occurring when tidal intensity was the greatest during full and new moons. The strongest seasonal pattern was observed in the south where no mantas were recorded during the first quarter in any year. This coincides with an increase in temperature and reduction of productivity in this region associated with monsoonal shifts. The long-term fidelity indicates that marine-protected areas centered around aggregation sites could help protect this species from overexploitation.     

Specialized bees fail to develop on non-host pollen: do plants chemically protect their pollen?

Bees require large amounts of pollen for their own reproduction. While several morphological flower traits are known to have evolved to protect plants against excessive pollen harvesting by bees, little is known on how selection to minimize pollen loss acts on the chemical composition of pollen. In this study, we traced the larval development of four solitary bee species, each specialized on a different pollen source, when reared on non-host pollen by transferring unhatched eggs of one species onto the pollen provisions of another species. Pollen diets of Asteraceae and Ranunculus (Ranunculaceae) proved to be inadequate for all bee species tested except those specialized on these plants. Further, pollen of Sinapis (Brassicaceae) and Echium (Boraginaceae) failed to support larval development in one bee species specialized on Campanula (Campanulaceae). Our results strongly suggest that pollen of these four taxonomic groups possess protective properties that hamper digestion and thus challenge the general view of pollen as an easy-to-use protein source for flower visitors.     

Selection toward shorter flowers by butterflies whose probosces are shorter than floral tubes

Darwin's meticulous observations on the function of floral shape led to his famous prediction of a long-tongued pollinator, which he believed to be the evolutionary trigger for the long-spurred flowers of the Madagascar star orchid. Although tubular flowers are common, long tubes or spurs are an exception, suggesting that selection maintaining short flowers is widespread. Using the butterfly-pollinated carnation Dianthus carthusianorum and two butterfly species differing in proboscis length (Melanargia galathea and Inachis io) as model organisms, we experimentally demonstrate a reduction in pollinator efficiency with an increasing difference between proboscis length and floral tube length. Such a relationship is a prerequisite for the evolution of floral shape in response to pollinator morphology.     

Investigating the potential for different scooter and car exhaust emissions to cause cytotoxic and (pro-)inflammatory responses to a 3D in vitro model of the human epithelial airway

The aim of this study was to compare the cytotoxicity and the (pro-)inflammatory responses of two-stroke (direct injection and carburetor technology) and four-stroke scooter and diesel car exhaust emissions on lung cells in vitro. This was analyzed by exposing a 3D in vitro model of the epithelial airway (consisting of human bronchial epithelial cells (cell line 16HBE14o^?) combined with human whole blood monocyte-derived macrophages and dendritic cells) to physically characterized exhaust emissions. Biological endpoints of cytotoxicity (lactate dehydrogenase release), as well as pro-inflammatory cytokine (tumor necrosis factor (TNF)-α) and inflammatory chemokine (interleukin(IL)-8) stimulation were examined. Two-stroke direct injection scooter exhaust contained the highest particle number concentration and nitrogen oxides (NO _x ) concentrations and the emissions from the two-stroke carburetor scooter contained the highest hydrocarbon and lowest NO _x concentrations. The four-stroke scooter emitted the highest carbon monoxide concentration whereas the cars emitted the lowest. The combination of various technical optimizations for the two-stroke direct injection scooter (particle filter, oxidative catalyst, better oil and fuel) reduced the total emissions strongly and the TNF-α concentration significantly (p?相似文献   

Reproductive seasonality is a poor predictor of receptive synchrony and male reproductive skew among nonhuman primates

Among nonhuman primates, male reproductive skew (i.e., the distribution of reproductive success across males) appears to be affected primarily by receptive synchrony and the number of males per group. These factors have been assumed to depend on reproductive seasonality, with strong seasonality increasing receptive synchrony, which in turn reduces the strength of male monopolization associated with more males and lower skew. Here we tested the importance of reproductive seasonality for 26 populations representing 15 species living in multimale groups. We obtained data from the literature on paternity, number of males per group, receptive synchrony, and three measures of seasonality of reproduction. We analyzed these data using bivariate regressions and hierarchical regression by sets and controlled for the effect of evolutionary relationships using phylogenetic generalized least squares. As expected, alpha male paternity decreased as the number of males per group increased as well as with increasing female receptive synchrony. Reproductive seasonality did not explain variation in reproductive skew over and above the variation explained by synchrony and the number of males. Reproductive seasonality alone only explained a small proportion of the variation in skew, and there was no strong association between reproductive seasonality and synchrony. The effects of receptive synchrony and reproductive seasonality as well as their link were reduced if we excluded captive populations. These results indicate that across primates male reproductive skew is related to the number of competitors in a group and that seasonality does not reliably predict synchrony or male reproductive skew.     

Contagious cooperation,temptation, and ecosystem collapse

Real world observations suggest that social norms of cooperation can be effective in overcoming social dilemmas such as the joint management of a common pool resource—but also that they can be subject to slow erosion and sudden collapse. We show that these patterns of erosion and collapse emerge endogenously in a model of a closed community harvesting a renewable natural resource in which individual agents face the temptation to overexploit the resource, while a cooperative harvesting norm spreads through the community via interpersonal relations. We analyze under what circumstances small changes in key parameters (including the size of the community, and the rate of technological progress) trigger catastrophic transitions from relatively high levels of cooperation to widespread norm violation—causing the social–ecological system to collapse.