Chemical Mediation of Prey Recognition by Spider-Hunting Wasps

Predator–prey interactions are important in maintaining the structure and dynamics of ecological communities. Both predators and prey use cues from a range of sensory modalities to detect and assess one another; identification of these cues is necessary to understand how selection operates to shape predator–prey interactions. Mud-dauber wasps (Sphecidae) provision their larval nests with paralyzed spiders, and different genera of wasps specialize on particular spider taxa. Sceliphron caementarium (Drury 1773) wasps preferentially capture spiders that build two-dimensional (2D) webs, rather than those that construct three-dimensional (3D) webs, but the basis of this preference is not clear. Wasps may choose spiders based on an assessment of their web architecture, as 3D webs may provide better defenses against wasp predation than do 2D webs. However, because many hymenopterans use chemical cues to locate and recognize prey, it is also possible that mud-dauber wasps rely on chemical cues associated with the spider and/or the web to assess prey suitability. When we offered foraging S. caementarium wasps 2D and 3D spiders both on and off their webs, we found that in both cases the wasps took 2D spiders and avoided 3D spiders, demonstrating that the web itself is not the impediment. Results of a series of behavioral choice assays involving filter paper discs containing spider cues and chemically manipulated spiders or spider dummies corroborated the importance of spider chemical cues in mediation of prey recognition by mud-dauber wasps. We also discuss the relative importance of visual and chemical cues for prey recognition by wasps, examine the anti-predator behaviors of 2D and 3D spiders, and consider the role of wasp predation in spider diversification.     

Hunting with Polar Bears: Problems with the Passive Properties of the Commons

Inuit in Canada’s Arctic conceptualize both human hunters and their polar bear prey as active participants in the hunt and as part of a larger socio-economic system requiring the involvement of both humans and animals. Although often treated through the lens of common-pool resource theory, the Inuit viewpoint conflicts with Western wildlife management systems that typically treat animals, and nature in general, as passive. When polar bears are understood as active participants in the hunt, the rights associated with common property regimes and assumptions about collective-choice decisions in common-pool resource management require significant revision. In this paper we argue that common-pool resource theories which assume natural resources are inherently passive cannot adequately account for the system of active relationships operating among Inuit in Arctic Canada. The co-management system of Nunavut Territory, Canada, uses a flexible quota approach, which, while following conservation guidelines, allows some space for the traditional Inuit-polar bear system to operate. This example shows how common-pool resources may be managed sustainably without the attendant assumption that natural resources exist passively outside of common-pool resource regimes.     

Nutritional effects of culture media on mycoplasma cell size and removal by filtration

Careful media filtration prior to use is an important part of a mycoplasma contamination prevention program. This study was conducted to increase our knowledge of factors that influence efficient filtration of mycoplasma. The cell size of Acholeplasma laidlawii was measured after culture in various nutritional conditions using scanning electron microscopy. The maximum cell size changed, but the minimum cell size remained virtually unchanged and all tested nutritional conditions resulted in a population of cells smaller than 0.2 μm. Culture in Tryptic Soy Broth (TSB) resulted in an apparent increase in the percentage of very small cells which was not reflected in increased penetration of non-retentive 0.2 μm rated filters. A. laidlawii cultured in selected media formulations was used to challenge 0.2 μm rated filters using mycoplasma broth base as the carrier fluid. We used 0.2 μm rated filters as an analytical tool because A. laidlawii is known to penetrate 0.2 μm filters and the degrees of penetration can be compared. Culture of A. laidlawii in TSB resulted in cells that did not penetrate 0.2 μm rated filters to the same degree as cells cultured in other media such as mycoplasma broth or in TSB supplemented with 10% horse serum.     

Bidirectional plasticity gated by hyperpolarization controls the gain of postsynaptic firing responses at central vestibular nerve synapses

Linking synaptic plasticity with behavioral learning requires understanding how synaptic efficacy influences postsynaptic firing in neurons whose role in behavior is understood. Here, we examine plasticity at a candidate site of motor learning: vestibular nerve synapses onto neurons that mediate reflexive movements. Pairing nerve activity with changes in postsynaptic voltage induced bidirectional synaptic plasticity in vestibular nucleus projection neurons: long-term potentiation relied on calcium-permeable AMPA receptors and postsynaptic hyperpolarization, whereas long-term depression relied on NMDA receptors and postsynaptic depolarization. Remarkably, both forms of plasticity uniformly scaled synaptic currents evoked by pulse trains, and these changes in synaptic efficacy were translated into linear increases or decreases in postsynaptic firing responses. Synapses onto local inhibitory neurons were also plastic but expressed only long-term depression. Bidirectional, linear gain control of vestibular nerve synapses onto projection neurons provides a plausible mechanism for motor learning underlying adaptation of vestibular reflexes.     

Wool-degrading <Emphasis Type="Italic">Bacillus</Emphasis> isolates: extracellular protease production for microbial processing of fabrics

Wool is a natural animal fiber commonly used in fabrics, but requires physical and chemical processing treatment for such applications. With the aim of developing new woollen textile products using environmentally friendly treatments, proteolytic bacteria were isolated from raw wool samples of Merino sheep and screened for wool-degrading activity. Two isolates were identified as Bacillus megaterium L4 and Bacillus thuringiensis L11 by 16S rRNA gene sequence analysis. Both isolates grew on a minimal medium using wool-fiber or wool-fabric as sole carbon and nitrogen sources. Bacterial growth was correlated with extracellular protease activity, and maximal protease production was in early stationary phase. The exoprotease produced by L11 was found to be a thermo-tolerant metalloprotease stabilized by calcium or magnesium, and had optimum activity at pH 7.0 and temperature at 40°C. During bacterial growth the wool-fiber lost weight, but it did not show changes in diameter. When wool-fabric was used instead of wool-fiber weight loss and non-shrinking was found. These are encouraging results for textile processing that should be useful for development of new textile products by direct microbial processing. A potential alternative that could be suggested from our study would be to treat wool with wool-degrading microorganisms in order to develop environmentally friendly processes.     

Altered DNA methylation in leukocytes with trisomy 21

The primary abnormality in Down syndrome (DS), trisomy 21, is well known; but how this chromosomal gain produces the complex DS phenotype, including immune system defects, is not well understood. We profiled DNA methylation in total peripheral blood leukocytes (PBL) and T-lymphocytes from adults with DS and normal controls and found gene-specific abnormalities of CpG methylation in DS, with many of the differentially methylated genes having known or predicted roles in lymphocyte development and function. Validation of the microarray data by bisulfite sequencing and methylation-sensitive Pyrosequencing (MS-Pyroseq) confirmed strong differences in methylation (p<0.0001) for each of 8 genes tested: TMEM131, TCF7, CD3Z/CD247, SH3BP2, EIF4E, PLD6, SUMO3, and CPT1B, in DS versus control PBL. In addition, we validated differential methylation of NOD2/CARD15 by bisulfite sequencing in DS versus control T-cells. The differentially methylated genes were found on various autosomes, with no enrichment on chromosome 21. Differences in methylation were generally stable in a given individual, remained significant after adjusting for age, and were not due to altered cell counts. Some but not all of the differentially methylated genes showed different mean mRNA expression in DS versus control PBL; and the altered expression of 5 of these genes, TMEM131, TCF7, CD3Z, NOD2, and NPDC1, was recapitulated by exposing normal lymphocytes to the demethylating drug 5-aza-2'deoxycytidine (5aza-dC) plus mitogens. We conclude that altered gene-specific DNA methylation is a recurrent and functionally relevant downstream response to trisomy 21 in human cells.