Induction of defenses and within-alga variation of palatability in two brown algae from the northern-central coast of Chile: effects of mesograzers and UV radiation.

Abstract Macroalgae possess different defense mechanisms in response to herbivory. Some species produce anti-herbivore secondary metabolites, but production of these substances can be costly. Therefore, algae may produce defensive metabolites only in response to herbivory (inducible defense) or defend particular parts of the alga differentially (within-alga variation). In the present study, we examined whether two species of brown algae from the SE-Pacific show evidence of inducible chemical defense (non-polar compounds) or within-alga variation of defense, which we estimated in form of palatability of differently treated algae to amphipod grazers (with live algae and agar-based food containing non-polar algal extracts). In Glossophora kunthii (C. Agardh) J. Agardh, we observed an increase in palatability after algae were acclimated for 12 days without grazers. Subsequent addition of grazers for 12 days then resulted in a reduction of palatability indicating the existence of inducible defense. After removal of grazers for 12 days, these induced effects again disappeared. The reaction of G. kunthii was triggered even by the mere presence of grazers, which suggests that this alga can respond to waterborne cues by reducing palatability. Effects were only found for agar-based food containing non-polar extracts, but not for live algae, suggesting that some parts of the algae are undefended. Our second experiment on within-alga variation confirmed that only apical (growth region) and basal parts (near the holdfast region) of G. kunthii are defended against herbivores. For the second species, Macrocystis integrifolia Bory, the first experiment revealed no induction of defense, while the second experiment on within-alga variation showed that amphipods avoided basal parts and in particular stipes of M. integrifolia but only in live algae. Although both studied algal species differed substantially in their defensive strategies, their reaction was independent of the presence or absence of UV radiation. Thus, it appears that UV effects play only a minor role in anti-herbivore defense, which is in accordance with most previous studies.

Geographic variation in fitness-related traits of the bladderwrack Fucus vesiculosus along the Baltic Sea-North Sea salinity gradient

In the course of the ongoing global intensification and diversification of human pressures, the study of variation patterns of biological traits along environmental gradients can provide relevant information on the performance of species under shifting conditions. The pronounced salinity gradient, co-occurrence of multiple stressors, and accelerated rates of change make the Baltic Sea and its transition to North Sea a suitable region for this type of study. Focusing on the bladderwrack Fucus vesiculosus, one of the main foundation species on hard-bottoms of the Baltic Sea, we analyzed the phenotypic variation among populations occurring along 2,000 km of coasts subjected to salinities from 4 to >30 and a variety of other stressors. Morphological and biochemical traits, including palatability for grazers, were recorded at 20 stations along the Baltic Sea and four stations in the North Sea. We evaluated in a common modeling framework the relative contribution of multiple environmental drivers to the observed trait patterns. Salinity was the main and, in some cases, the only environmental driver of the geographic trait variation in F. vesiculosus. The decrease in salinity from North Sea to Baltic Sea stations was accompanied by a decline in thallus size, photosynthetic pigments, and energy storage compounds, and affected the interaction of the alga with herbivores and epibiota. For some traits, drivers that vary locally such as wave exposure, light availability or nutrient enrichment were also important. The strong genetic population structure in this macroalgae might play a role in the generation and maintenance of phenotypic patterns across geographic scales. In light of our results, the desalination process projected for the Baltic Sea could have detrimental impacts on F. vesiculosus in areas close to its tolerance limit, affecting ecosystem functions such as habitat formation, primary production, and food supply.Peer reviewe

The capacity of short-chain fructo-oligosaccharides to stimulate faecal bifidobacteria: a dose-response relationship study in healthy humans

BACKGROUND: Short-chain fructo-oligosaccharides (scFOS) are well-known for their bifidogenicity. In a large study comprising 200 healthy volunteers, we determined the bifidogenic properties of 7 non-digestible carbohydrates administered at a dose of 10 g/d in the diet; we analysed dose-response relationships of the bifidogenic substrates at doses ranging from 2.5 to 10 g/d in comparison with a placebo. The aim of this presentation is to give more details about the dose-response effects of short-chain fructo-oligosaccharides (scFOS). METHODS: Forty healthy volunteers (18 males, 22 females) eating their usual diets were randomly divided into 5 groups of 8 subjects and received scFOS at a dose of 2.5, 5.0, 7.5 and 10 g/d or a placebo for 7 d. Stools were collected before (day (d) 8) and at the end (day (d) 15) of sugar consumption, and tolerance was evaluated using a daily chart. RESULTS (M ± SEM): Bifidobacteria counts increase was higher in scFOS than in placebo group for all doses tested [2.5 g/d (from 9.15 ± 0.59 to 9.39 ± 0.70; P = 0.02); 5 g/d (from 10.21 ± 0.21 to 10.67 ± 0.22; P = 0.03); 7.5 g/d (from 9.28 ± 0.49 to 9.85 ± 0.35;P = 0.01); 10 g/d (from 9.00 ± 0.81 to 10.18 ± 0.60; P = 0.003)]. A significant correlation between the ingested dose of scFOS and faecal bifidobacteria counts was observed at d15 (r(2 )= 0.307, P < 0.001). Total anaerobes increased at the dose of 10 g/d. No significant differences were found for Bacteroides, Lactobacillus, enterobacteria or pH in any group. The frequency of digestive symptoms was not different between scFOS at any of the doses tested and placebo. Bloating was significantly more intense during scFOS ingestion at doses of 2.5 and 5 g/d, but not at doses of 7.5 and 10 g/d. Excess flatus, borborygmi and abdominal pain did not differ from the placebo at any of the doses tested. CONCLUSION: This study showed that scFOS is bifidogenic and well tolerated at doses ranging from 2.5 to 10 g/d, and that there is a dose-response relationship in healthy volunteers

Re-structuring of marine communities exposed to environmental change: a global study on the interactive effects of species and functional richness

Species richness is the most commonly used but controversial biodiversity metric in studies on aspects of community stability such as structural composition or productivity. The apparent ambiguity of theoretical and experimental findings may in part be due to experimental shortcomings and/or heterogeneity of scales and methods in earlier studies. This has led to an urgent call for improved and more realistic experiments. In a series of experiments replicated at a global scale we translocated several hundred marine hard bottom communities to new environments simulating a rapid but moderate environmental change. Subsequently, we measured their rate of compositional change (re-structuring) which in the great majority of cases represented a compositional convergence towards local communities. Re-structuring is driven by mortality of community components (original species) and establishment of new species in the changed environmental context. The rate of this re-structuring was then related to various system properties. We show that availability of free substratum relates negatively while taxon richness relates positively to structural persistence (i.e., no or slow re-structuring). Thus, when faced with environmental change, taxon-rich communities retain their original composition longer than taxon-poor communities. The effect of taxon richness, however, interacts with another aspect of diversity, functional richness. Indeed, taxon richness relates positively to persistence in functionally depauperate communities, but not in functionally diverse communities. The interaction between taxonomic and functional diversity with regard to the behaviour of communities exposed to environmental stress may help understand some of the seemingly contrasting findings of past research.Mercator Stiftung via GAMEPostprint4,41

Four-week short chain fructo-oligosaccharides ingestion leads to increasing fecal bifidobacteria and cholesterol excretion in healthy elderly volunteers

<p>Abstract</p> <p>Background</p> <p>Short-chain fructo-oligosaccharides (scFOS) are increasingly used in human diet for their prebiotic properties. We aimed at investigating the effects of scFOS ingestion on the colonic microflora and oro-fecal transit time in elderly healthy humans.</p> <p>Methods</p> <p>Stools composition, oro-fecal transit time, and clinical tolerance were evaluated in 12 healthy volunteers, aged 69 ± 2 yrs, in three consecutive periods: basal period (2 weeks), scFOS (Actilight^®) ingestion period (8 g/d for 4 weeks) and follow-up period (4 weeks). Two-way ANOVA, with time and treatment as factors, was used to compare the main outcome measures between the three periods.</p> <p>Results</p> <p>Fecal bifidobacteria counts were significantly increased during the scFOS period (9.17 ± 0.17 log cfu/g vs 8.52 ± 0.26 log cfu/g during the basal period) and returned to their initial values at the end of follow-up (8.37 ± 0.21 log cfu/g; P < 0.05). Fecal cholesterol concentration increased during the scFOS period (8.18 ± 2.37 mg/g dry matter vs 2.81 ± 0.94 mg/g dry matter during the basal period) and returned to the baseline value at the end of follow-up (2.87 ± 0.44 mg/g dry matter; P < 0.05). Fecal pH tended to decrease during scFOS ingestion and follow-up periods compared to the basal period (P = 0.06). Fecal bile acids, stool weight, water percentage, and oro-fecal transit time did not change throughout the study. Excess flatus and bloating were significantly more frequent during scFOS ingestion when compared to the basal period (P < 0.05), but the intensity of these symptoms was very mild.</p> <p>Conclusion</p> <p>Four-week 8 g/d scFOS ingestion is well tolerated and leads to a significant increase in fecal bifidobacteria in healthy elderly subjects. Whether the change in cholesterol metabolism found in our study could exert a beneficial action warrants further studies.</p

Geographic variation in fitness-related traits of the bladderwrack Fucus vesiculosus along the Baltic Sea-North Sea salinity gradient

In the course of the ongoing global intensification and diversification of human pressures, the study of variation patterns of biological traits along environmental gradients can provide relevant information on the performance of species under shifting conditions. The pronounced salinity gradient, co-occurrence of multiple stressors, and accelerated rates of change make the Baltic Sea and its transition to North Sea a suitable region for this type of study. Focusing on the bladderwrack Fucus vesiculosus, one of the main foundation species on hard-bottoms of the Baltic Sea, we analyzed the phenotypic variation among populations occurring along 2,000 km of coasts subjected to salinities from 4 to >30 and a variety of other stressors. Morphological and biochemical traits, including palatability for grazers, were recorded at 20 stations along the Baltic Sea and four stations in the North Sea. We evaluated in a common modeling framework the relative contribution of multiple environmental drivers to the observed trait patterns. Salinity was the main and, in some cases, the only environmental driver of the geographic trait variation in F. vesiculosus. The decrease in salinity from North Sea to Baltic Sea stations was accompanied by a decline in thallus size, photosynthetic pigments, and energy storage compounds, and affected the interaction of the alga with herbivores and epibiota. For some traits, drivers that vary locally such as wave exposure, light availability or nutrient enrichment were also important. The strong genetic population structure in this macroalgae might play a role in the generation and maintenance of phenotypic patterns across geographic scales. In light of our results, the desalination process projected for the Baltic Sea could have detrimental impacts on F. vesiculosus in areas close to its tolerance limit, affecting ecosystem functions such as habitat formation, primary production, and food supply

Stressed but Stable: Canopy Loss Decreased Species Synchrony and Metabolic Variability in an Intertidal Hard-Bottom Community

The temporal stability of aggregate community properties depends on the dynamics of the component species. Since species growth can compensate for the decline of other species, synchronous species dynamics can maintain stability (i.e. invariability) in aggregate properties such as community abundance and metabolism. In field experiments we tested the separate and interactive effects of two stressors associated with storminess–loss of a canopy-forming species and mechanical disturbances–on species synchrony and community respiration of intertidal hard-bottom communities on Helgoland Island, NE Atlantic. Treatments consisted of regular removal of the canopy-forming seaweed Fucus serratus and a mechanical disturbance applied once at the onset of the experiment in March 2006. The level of synchrony in species abundances was assessed from estimates of species percentage cover every three months until September 2007. Experiments at two sites consistently showed that canopy loss significantly reduced species synchrony. Mechanical disturbance had neither separate nor interactive effects on species synchrony. Accordingly, in situ measurements of CO2-fluxes showed that canopy loss, but not mechanical disturbances, significantly reduced net primary productivity and temporal variation in community respiration during emersion periods. Our results support the idea that compensatory dynamics may stabilise aggregate properties. They further suggest that the ecological consequences of the loss of a single structurally important species may be stronger than those derived from smaller-scale mechanical disturbances in natural ecosystems

Preventive and curative effect of melatonin on mammary carcinogenesis induced by dimethylbenz[a]anthracene in the female Sprague–Dawley rat

INTRODUCTION: It has been well documented that the pineal hormone, melatonin, which plays a major role in the control of reproduction in mammals, also plays a role in the incidence and growth of breast and mammary cancer. The curative effect of melatonin on the growth of dimethylbenz [a]anthracene-induced (DMBA-induced) mammary adenocarcinoma (ADK) has been previously well documented in the female Sprague–Dawley rat. However, the preventive effect of melatonin in limiting the frequency of cancer initiation has not been well documented. METHODS: The aim of this study was to compare the potency of melatonin to limit the frequency of mammary cancer initiation with its potency to inhibit tumor progression once initiation, at 55 days of age, was achieved. The present study compared the effect of preventive treatment with melatonin (10 mg/kg daily) administered for only 15 days before the administration of DMBA with the effect of long-term (6-month) curative treatment with the same dose of melatonin starting the day after DMBA administration. The rats were followed up for a year after the administration of the DMBA. RESULTS: The results clearly showed almost identical preventive and curative effects of melatonin on the growth of DMBA-induced mammary ADK. Many hypotheses have been proposed to explain the inhibitory effects of melatonin. However, the mechanisms responsible for its strong preventive effect are still a matter of debate. At least, it can be envisaged that the artificial amplification of the intensity of the circadian rhythm of melatonin could markedly reduce the DNA damage provoked by DMBA and therefore the frequency of cancer initiation. CONCLUSION: In view of the present results, obtained in the female Sprague–Dawley rat, it can be envisaged that the long-term inhibition of mammary ADK promotion by a brief, preventive treatment with melatonin could also reduce the risk of breast cancer induced in women by unidentified environmental factors