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Nutrient Assimilation (nutrient + assimilation)
Selected AbstractsPost-ingestive effects of nectar alkaloids depend on dominance status of bumblebeesECOLOGICAL ENTOMOLOGY, Issue 4 2009JESSAMYN S. MANSON Abstract 1.,Secondary metabolites have acute or chronic post-ingestive effects on animals, ranging from death to growth inhibition to reduced nutrient assimilation. 2.,Although characterised as toxic, the nectar of Gelsemium sempervirens is not lethal to pollinators, even when the concentration of the nectar alkaloid gelsemine is very high. However, little is known about the sublethal costs of nectar alkaloids. 3.,Using a microcolony assay and paired worker bumblebees, the present study measured the effects of artificial nectar containing gelsemine on oocyte development. Oocytes are a sensitive indicator of protein utilisation and general metabolic processes. We also calculated carbohydrate concentrations in the haemolymph to examine energetic costs of gelsemine consumption. 4.,High concentrations of gelsemine significantly reduced mean oocyte width in subordinate bees, while dominant bees showed only a trend towards oocyte inhibition. Gelsemine consumption did not reduce carbohydrate concentrations in haemolymph. 5.,The cost of ingesting gelsemine may be due to direct toxicity of alkaloids or may be an expense associated with detoxifying gelsemine. Detoxification of alkaloids can require reallocation of resources away from essential metabolic functions like reproduction. The risks associated with nectar alkaloid consumption are tied to both the social and nutritional status of the bee. [source] Nutrient cycling efficiency explains the long-term effect of ecosystem engineers on primary productionFUNCTIONAL ECOLOGY, Issue 1 2007SÉBASTIEN BAROT Summary 1Soil organisms, such as earthworms, accelerate mineralization of soil organic matter and are thought to be beneficial for plant growth. This has been shown in short-term microcosm experiments. It is thus legitimate to ask whether these increases in plant growth are due to brief pulses of mineralization or whether these increases are long-lasting. 2This question was addressed using a system of differential equations modelling the effects of decomposers on nutrient cycling via trophic (nutrient assimilation) and nontrophic effects (through their ecosystem engineering activities). 3The analytical study of this model showed that these processes increase primary production in the long term when they recycle nutrients efficiently, allowing a small fraction of the recycled nutrients to be leached out of the ecosystem. 4Mineralization by the ecosystem engineering activities of decomposers seems to deprive them of a resource. However, it was shown that a decomposer may increase its own biomass, through its ecosystem engineering activities, provided the created recycling loop is efficient enough. 5Mechanisms through which earthworms may modify the efficiency of nutrient cycling are discussed. The necessity of measuring the effect of earthworms on the nutrient input,output balance of ecosystems under field conditions is emphasized. [source] Ants mediate foliar structure and nitrogen acquisition in a tank-bromeliadNEW PHYTOLOGIST, Issue 4 2009Céline Leroy Summary ,,Aechmea mertensii is a tank-bromeliad that roots on ant-gardens initiated by the ants Camponotus femoratus and Pachycondyla goeldii. Its leaves form compartments acting as phytotelmata that hold rainwater and provide habitats for invertebrates. In this article, we aimed to determine whether the association with either C. femoratus or P. goeldii influenced the vegetative traits of A. mertensii, invertebrate diversity and nutrient assimilation by the leaves. ,,Transmitted light, vegetative traits and phytotelmata contents were compared between the two A. mertensii ant-gardens. ,,Camponotus femoratus colonized partially shaded areas, whereas P. goeldii colonized exposed areas. The bromeliads' rosettes had a large canopy (C. femoratus ant-gardens), or were smaller and amphora shaped (P. goeldii ant-gardens). There were significant differences in leaf anatomy, as shaded leaves were thicker than exposed leaves. The mean volumes of water, fine particulate organic matter and detritus in C. femoratus -associated bromeliads were three to five times higher than in P. goeldii -associated bromeliads. Moreover, the highest invertebrate diversity and leaf ,15N values were found in C. femoratus -associated bromeliads. ,,This study enhances our understanding of the dynamics of biodiversity, and shows how ant,plant interactions can have trophic consequences and thus influence the architecture of the interacting plant via a complex feedback loop. [source] Are fecundity and longevity of female Aphelinus abdominalis affected by development in GNA-dosed Macrosiphum euphorbiae?PHYSIOLOGICAL ENTOMOLOGY, Issue 4 2001A. Couty Abstract. Snowdrop lectin (Galanthus nivalis agglutinin, GNA) confers partial resistance to several aphid species when incorporated into an artificial diet and/or expressed in transgenic potato. First-tier laboratory-scale experiments were conducted to assess the potential effect of GNA on the longevity and fecundity of female parasitoid Aphelinus abdominalis (Dalman) that had developed in Macrosiphum euphorbiae (Thomas) fed artificial diet containing 0.1% GNA (w/v). In a previous study it was shown that GNA ingested by A. abdominalis larvae is not acutely toxic. It was also shown that GNA has a host-size mediated effect on parasitoid sex ratio and larval development, but no apparent direct effect. In this study, we report that A. abdominalis larvae that developed in GNA-dosed aphids that were smaller than control aphids of the same age, produced smaller adults with a reduced longevity and fecundity. Aphelinus abdominalis larvae that developed in GNA-dosed aphids older than the control but of the same size, produced adults of similar size that lived as long as the control but had a reduced fecundity. Our results suggest that GNA fed to aphids in artificial diet has both a host-mediated effect (via aphid-size) and a direct effect on adult parasitoid fecundity. It is not known how GNA affects parasitoid larval development and subsequently adult fecundity, but it is hypothesized that GNA acted as an antifeedant to parasitoid larvae, thus disturbing nutrient assimilation and conversion necessary for egg maturation. [source] Growth of the vacuoleless mutant of Tetrahymena thermophila NP1 in phytateTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005SAMANTHA WEBB Phytate, the salt form of phytic acid, is the major store of phosphate in seeds and grain. Since non-ruminant farm animals poorly digest phytate, it is also a source of environmental phosphate contamination in agricultural areas. We are using Tetrahymena, a ciliated protist with multiple routes for nutrient assimilation, as a model to investigate the contribution of heterotrophic protists to the environmental cycling of phosphate from phytate. This ciliate has the ability to grow on phytate as the sole phosphate source (Ziemkiewicz, H. T., Johnson, M. D. & Smith-Somerville, H. E. 2002. J. Eukaryot. Microbiol., 49:428). Tetrahymena thermophila NP1, a temperature-sensitive vacuoleless mutant (ATCC #50202), provides a way to separate membrane transport from uptake through phagosomes, and to assess the importance of each mechanism. This cell grows equally well at the permissive and non-permissive temperatures with either phytate or inorganic phosphate as the phosphate source. Our results demonstrate that phagosomes are not required to use the phosphate from phytate. [source] | ||||||||||