Allelopathic interactions between the brown algal genus Lobophora (Dictyotales, Phaeophyceae) and scleractinian corals

Allelopathy has been recently suggested as a mechanism by which macroalgae may outcompete corals in damaged reefs. Members of the brown algal genus Lobophora are commonly observed in close contact with scleractinian corals and have been considered responsible for negative effects of macroalgae to scleractinian corals. Recent field assays have suggested the potential role of chemical mediators in this interaction. We performed in situ bioassays testing the allelopathy of crude extracts and isolated compounds of several Lobophora species, naturally associated or not with corals, against four corals in New Caledonia. Our results showed that, regardless of their natural association with corals, organic extracts from species of the genus Lobophora are intrinsically capable of bleaching some coral species upon direct contact. Additionally, three new C-21 polyunsaturated alcohols named lobophorenols A-C (1-3) were isolated and identified. Significant all elopathic effects against Acropora muricata were identified for these compounds. In situ observations in New Caledonia, however, indicated that while allelopathic interactions are likely to occur at the macroalgal-coral interface, Lobophora spp. rarely bleached their coral hosts. These findings are important toward our understanding of the importance of allelopathy versus other processes such as herbivory in the interaction between macroalgae and corals in reef ecosystems

Biochemical Trade-Offs: Evidence for Ecologically Linked Secondary Metabolism of the Sponge Oscarella balibaloi

Secondary metabolite production is assumed to be costly and therefore the resource allocation to their production should be optimized with respect to primary biological functions such as growth or reproduction. Sponges are known to produce a great diversity of secondary metabolites with powerful biological activities that may explain their domination in some hard substrate communities both in terms of diversity and biomass. Oscarella balibaloi (Homoscleromorpha) is a recently described, highly dynamic species, which often overgrows other sessile marine invertebrates. Bioactivity measurements (standardized Microtox assay) and metabolic fingerprints were used as indicators of the baseline variations of the O. balibaloi secondary metabolism, and related to the sponge reproductive effort over two years. The bioactivity showed a significant seasonal variation with the lowest values at the end of spring and in early summer followed by the highest bioactivity in the late summer and autumn. An effect of the seawater temperature was detected, with a significantly higher bioactivity in warm conditions. There was also a tendency of a higher bioactivity when O. balibaloi was found overgrowing other sponge species. Metabolic fingerprints revealed the existence of three principal metabolic phenotypes: phenotype 1 exhibited by a majority of low bioactive, female individuals, whereas phenotypes 2 and 3 correspond to a majority of highly bioactive, non-reproductive individuals. The bioactivity was negatively correlated to the reproductive effort, minimal bioactivities coinciding with the period of embryogenesis and larval development. Our results fit the Optimal Defense Theory with an investment in the reproduction mainly shaping the secondary metabolism variability, and a less pronounced influence of other biotic (species interaction) and abiotic (temperature) factors

From Topology to Quasi-Topology. The Complexity of the Notional Domain

This article examines a fundamental metalinguistic construction of the theory of enunciative operations: the notional domain. In particular, we try to explain some elementary topological concepts on which this construction is based and we try to show the key role they play in the description of some basic linguistic operations

Post mortem changes in the mechanical properties and ultrastructure of the Longissimus in two porcine breeds

Kinetics of postmortem muscle changes of two pig breeds were studied. pH was measured at 30 min (pH1) and 26 h (pH2) after slaughter. The longissimus thoracis et lumborum was used at 1, 2, 3, 6 and 14 days postmortem for measurements of sarcomere length and mechanical properties in the raw state, and cooking loss and mechanical properties after cooking. Electron microscopy was performed at 1, 6 and 14 days postmortem. pH1 was higher and the maximum stress lower in Large Whites than in Pietrains. Maximum stress of cooked meat decreased with aging time in Large Whites but not in Pietrains. Ultrastructural changes were more obvious in Large Whites than in Pietrains through day 6, but breed differences were no longer observed at day 14. Meat from Pietrain pigs was tougher than that from Large White pigs and tenderized at a slower rate and to a lesser extent during aging

Le rôle de la connaissance scientifique dans la création et la gestion d'une aire marine protégée transfrontalière : exemple des bouches de Bonifacio

Cancemi-Soullard Maddy, Culioli Jean-Michel, Frisoni G.-F. Le rôle de la connaissance scientifique dans la création et la gestion d'une aire marine protégée transfrontalière : exemple des bouches de Bonifacio . In: Revue d'Écologie (La Terre et La Vie), tome 59, n°1-2, 2004. p. 353

Photographic image analysis for the classification of bovine meat

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