Downy mildew (Plasmopara viticola) epidemics on grapevine under climate change

As climate is a key agro‐ecosystem driving force, climate change could have a severe impact on agriculture. Many assessments have been carried out to date on the possible effects of climate change (temperature, precipitation and carbon dioxide concentration changes) on plant physiology. At present however, likely effects on plant pathogens have not been investigated deeply. The aim of this work was to simulate future scenarios of downy mildew (Plasmopara viticola) epidemics on grape under climate change, by combining a disease model to output from two general circulation models (GCMs). Model runs corresponding to the SRES‐A2 emissions scenario, characterized by high projections of both population and greenhouse gas emissions from present to 2100, were chosen in order to investigate impacts of worst‐case scenarios, among those currently available from IPCC. Three future decades were simulated (2030, 2050, 2080), using as baseline historical series of meteorological data collected from 1955 to 2001 in Acqui Terme, an important grape‐growing area in the north‐west of Italy. Both GCMs predicted increase of temperature and decrease of precipitation in this region. The simulations obtained by combining the disease model to the two GCM outputs predicted an increase of the disease pressure in each decade: more severe epidemics were a direct consequence of more favourable temperature conditions during the months of May and June. These negative effects of increasing temperatures more than counterbalanced the effects of precipitation reductions, which alone would have diminished disease pressure. Results suggested that, as adaptation response to future climate change, more attention would have to be paid in the management of early downy mildew infections; two more fungicide sprays were necessary under the most negative climate scenario, compared with present management regimes. At the same time, increased knowledge on the effects of climate change on host–pathogen interactions will be necessary to improve current predictions.     

Deep phylogeographic divisions and long‐term persistence of forest invertebrates (Hexapoda: Collembola) in the North‐Western Mediterranean basin

The North‐Western Mediterranean basin is well known for its high number of relictual endemic taxa, and has been indicated as one of the world’s major biodiversity hotspots at the species level. A possible contributing factor may be long‐term persistence of populations and their prolonged stability. This study was designed to investigate the phylogeographic structure of three common species of the genus Lepidocyrtus (Hexapoda: Collembola), soil‐dwelling arthropods characterized by limited dispersal capabilities and generally associated with forest habitats. We observed a remarkable geographic structure, with numerous deeply divergent genetic lineages occupying islands as well as mainland sites with no apparent gene flow among most sites, even across distances of only tens of kilometres. The reconstructed time frame for the evolution of these lineages suggests divergence between 5 and 15 Ma. This indicates a remarkably ancient origin and long‐term persistence of individual lineages over a fine geographic scale despite the occurrence of abrupt sea level and climatic fluctuations in the area. This further suggests that currently recognized morphological species might be a serious underestimation of the true springtail biodiversity within this region.     

Action Mechanisms of the Secondary Metabolite Euplotin C: Signaling and Functional Role in Euplotes

ABSTRACT. Among secondary metabolites, the acetylated hemiacetal sesquiterpene euplotin C has been isolated from the marine, ciliated protist Euplotes crassus, and provides an effective mechanism for reducing populations of potential competitors through its cytotoxic properties. However, intracellular signaling mechanisms and their functional correlates mediating the ecological role of euplotin C are largely unknown. We report here that, in E. vannus (an Euplotes morphospecies that does not produce euplotin C and shares with E. crasssus the same interstitial habitat), euplotin C rapidly increases the intracellular concentration of both Ca²⁺ and Na⁺, suggesting a generalized effect of this metabolite on cation transport systems. In addition, euplotin C does not induce oxidative stress, but modulates the electrical properties of E. vannus through an increase of the amplitude of graded action potentials. These events parallel the disassembling of the ciliary structures, the inhibition of cell motility, the occurrence of aberrant cytoplasmic vacuoles, and the rapid inhibition of phagocytic activity. Euplotin C also increases lysosomal pH and decreases lysosomal membrane stability of E. vannus. These results suggest that euplotin C exerts a marked disruption of those homeostatic mechanisms whose efficiency represents the essential prerequisite to face the challenges of the interstitial environment.     

The effects of ethylene concentration in controlled atmosphere storage of tomatoes

Previous studies have demonstrated that mature green tomatoes can be stored for up to 10 wk at 12. 5°C, 93–95% r.h. in a controlled atmosphere (CA) containing 5% CO ₂ , 5% O₂ and 90% N ₂ , and will then ripen satisfactorily in air at 20°C. The effects of different concentrations of ethylene between <0.1 and 30 μl/litre in this storage atmosphere on ripening changes and fruit quality after 5 wk CA storage and a further 8 or 9 days ripening in air were investigated using cv. Sonatine glasshouse tomatoes. Maintaining ethylene concentrations in the storage atmosphere to.1 plllitre resulted in poor and uneven ripening of the tomatoes after storage, and increased their susceptibility to infection by Botrytis cinerea and Penicillium spp. Fruit previously stored in atmospheres containing 5 to 30 μl/litre ethylene were significantly softer after ripening than tomatoes stored in lower ethylene concentrations. Overall, the best results in terms of fruit quality (colour, firmness) and a low incidence of fungal infection were achieved with 1–3 μl/litre ethylene. The practical problems in achieving and maintaining optimum conditions, including the correct ethylene level, in CA storage of tomatoes are also discussed.     

Energy maximization and foraging strategies in Potamon fluviatile (Decapoda, Brachyura)

SUMMARY. 1 Foraging of the freshwater crab Potamon fluviatile was studied by recording the activity of seventy-eight specimens in a 50 m² pool in a Tuscan stream during early summer. Foraging was related both to the organic content of the substrate and to the crabs' oxygen consumption. During this period, adult females underwent "second vitellogenesis". with abundant deposition of yolk in oocytes.
2. A dispotic distribution (not accompanied by agonistic interactions, but 'peacefully' based on size) was observed within the foraging area. Larger animals (mostly males) fed on the rare patches of vegetable debris, which presented the highest organic content. Conversely, smaller specimens were relegated lo the poorer substrates, such as the stream banks.
3. The females extended and diversified their foraging areas by also venturing into terrestrial habitats, in contrast to the more sedentary and aquatic males. This behaviour (which was not accompanied by a different energetic output) resulted in a more proteinaceous diet (even when the N-content of vegetable debris fell drastically), and in a significant increase in fats and the hepatopancreas index.
4. The reserves of energetic substances are presumed to sustain the highly expensive vitellogenesis, with the production of macrolecithal eggs. The females' behaviour as energy maximizers' seemed to be under a strong selective pressure, since their reproductive success is directly related to the efficient harvesting of food.     

Trends and methodological impacts in soil CO2 efflux partitioning: A metaanalytical review

Partitioning soil carbon dioxide (CO₂) efflux (R_S) into autotrophic (R_A; including plant roots and closely associated organisms) and heterotrophic (R_H) components has received considerable attention, as differential responses of these components to environmental change have profound implications for the soil and ecosystem C balance. The increasing number of partitioning studies allows a more detailed analysis of experimental constraints than was previously possible. We present results of an exhaustive literature search of partitioning studies and analyse global trends in flux partitioning between biomes and ecosystem types by means of a metaanalysis. Across all data, an overall decline in the R_H/R_S ratio for increasing annual R_S fluxes emerged. For forest ecosystems, boreal coniferous sites showed significantly higher (P<0.05) R_H/R_S ratios than temperate sites, while both temperate or tropical deciduous forests did not differ in ratios from any of the other forest types. While chronosequence studies report consistent declines in the R_H/R_S ratio with age, no difference could be detected for different age groups in the global data set. Different methodologies showed generally good agreement if the range of R_S under which they had been measured was considered, with the exception of studies estimating R_H by means of root mass regressions against R_S, which resulted in consistently lower R_H/R_S estimates out of all methods included. Additionally, the time step over which fluxes were partitioned did not affect R_H/R_S ratios consistently. To put results into context, we review the most common techniques and point out the likely sources of errors associated with them. In order to improve soil CO₂ efflux partitioning in future experiments, we include methodological recommendations, and also highlight the potential interactions between soil components that may be overlooked as a consequence of the partitioning process itself.     

Regio and stereospecific DNA adduct formation in mouse lung at N6 and N7 position of adenine and guanine after 1,3 butadiene inhalation exposure

Butadiene monoepoxide (BMO) alkylated guanine N7 and adenine N 6 adducts were prepared and enriched by solid phase extraction and HPLC. The purified adducts were analysed by a modified 32P-postlabelling assay, which utilized one dimensional TLC chromatography and a subsequent HPLC analysis with UV and radioactivity detectors. In vitro with Ct-DNA the formation of N7-dGMP and N 6-dAMP adducts were linear at a concentration range of 44 to 870 nmol of BMO per mg DNA at physiological pH. N7- dGMP and N 6-dAMP adducts were formed in a ratio of 200:1. In dGMP and in dAMP 48 % and 86 % of adducts were covalently bound to the C-2 carbon of BMO. CD-1 mice were inhalation exposed to butadiene for 5 days and 6 h per day. The N7-dGMP adduct level in lung samples of animals exposed to 200, 500 and 1300 ppm was 2.8 +/- 0.9 fmol, 11 +/- 2.0 fmol and 30 +/- 6.7 fmol in 10 mug DNA, respectively. The level of N 6-dAMP adducts in lung samples after 500 ppm and 1300 ppm exposure was 0.09 +/- 0.06 fmol and 0.11 +/- 0.05 fmol in 10 mug DNA. At 200 ppm the adduct level was below the detection limit. A sub-group of animals exposed to 1300 ppm was killed 3 weeks after the last exposure. N7-dGMP adducts were not detected but the level of N 6-dAMP adducts was not affected. N7-dGMP adducts were formed in a clear stereospecific manner in vivo. S -BMO adducts were the main product and represented 77 % (n = 4, SD = 2%) of total BMO adducts. No clear conclusion can be drawn about the enantiospecific DNA binding at the N 6 position of dAMP, because of the poor separation of the enantiomers. However, we could separate regioisomeric adducts which indicated that C-2 adducts represented 69 +/- 3 % of the total N 6 adducts formed in mice lung DNA. This observation is supported by the data derived from in vitro DNA experiments but is different to our previously published data, which indicates the 2:1 (C-1:C-2) ratio in regioisomer formation in nucleotides or nucleosides. We suggest that the data presented in this communication indicate a different mechanism between nucleotides and DNA in BMO-derived adduct formation- Dimroth rearrangement dominates in nucleotides, but in double stranded DNA a direct alkylation is probably the major mechanism of adduct formation.     

Female gametes of the black coral Cirrhipathes cfr. anguina (Anthozoa,Antipatharia) from the Indonesian Marine Park of Bunaken

Summary

Female polyps of Cirrhipathes cfr. anguina were collected in August 2007 from the coral reef of Siladen Island in the Bunaken Marine Park (North Sulawesi, Indonesia). The primary transverse mesenteries, which separate the adjacent lateral tentacles from one another, were filled with oocytes developing within the mesoglea. Cross-sections of the oral region revealed that young gametes were located both at the emergence of the primary transverse mesenteries from the gastroderm lining the coelenterons, and at the point where the mesenteries were linked to the pharynx. By contrast, at a lower level, where the mesenteries gave rise to mesenterial filaments, young gametes were limited to the initial part of the mesenteries. Oocytes were lodged in individual chambers, and were separated from one another by mesogleal elements. On occasion, oocytes were found in proximity to cells with short microvillous-like processes that interdigitated with those emerging from the oocyte surface. Oocytes varied in size according to the stage of the vitellogenetic process, the largest measuring 125 μm in diameter. Their cytoplasm was enriched with inclusions of three main kinds: lipids, yolk and both rod- and ovoid-shaped bodies. These bodies were characterized by an electron-dense core with a dotted appearance, surrounded by a sequence of tightly-packed fibrils arranged in parallel fashion. These bodies pushed the oocyte membrane slightly outwards, giving rise to irregular “spiny” protrusions. In addition to the microvillous-like extensions, oocytes also showed short lobose pseudopodia; both are probably involved in nutrient uptake. No other membrane specializations were observed in the oocytes, the general morphology of which seemed to be coherent with the assumption that they had reached their final stage of growth. Investigations on the reproduction of the black coral may provide insights into the feasibility of transplanting fertile colonies into areas where they have been decimated by anthropogenic pressure.     

Assessing mate size in the red swamp crayfish Procambarus clarkii: effects of visual versus chemical stimuli

1. Mate assessment requires an efficient system of information exchange between the sexes and often relies on several forms of communication. Both sexes of the crayfish, Procambarus clarkii , select a mate on the basis of its body size, independently of chelar size/symmetry and dominance status, large size being a proxy for a high quality partner. Here, we explored the effects that visual and chemical stimuli, emitted alone or in combination, exert on the assessment of size of a potential mate.
2. We followed a binary choice test paradigm, in which two male or female 'targets', of either large or small size, were simultaneously presented to a female or a male 'chooser'. We recorded the first target visited, the total duration of the visits per target, and the behaviour of the chooser when approaching the target area.
3. Our results show that females require a combination of visual and chemical stimuli to select the larger male. A more complex pattern was found when males were the choosers. While visual and chemical cues together rendered them willing to mate with the larger female, their initial choice and the total time spent near her depended only on smell. In mate assessment by P. clarkii , visual and chemical information seem to act as 'non-redundant signals'.