Les reptiles sont sans doute parmi les animaux qui véhiculent le plus de préjugés : froids, visqueux, sournois, venimeux, brutes arriérées et stupides… La réalité est néanmoins bien différente et ces animaux ne sont en rien ce que l’on croit. La culture conditionne considérablement notre vision des reptiles, et les faits scientifiques, la réalité biologique, ont bien sur mal à rétablir la vérité et à changer la crainte voir la haine ordinaire envers les serpents, lézards, crocodiles… Même quand il s’agit de faire de la vulgarisation scientifique, les reptiles sont utilisés à mauvais escient : montrés comme des chainons manquants, témoins de l’âge des dinosaures qui n’auraient plus évolué, ils illustrent souvent de manière erronée les mécanismes de l’évolution. Ce sont aussi des animaux menacés : après les amphibiens, les reptiles sont le groupe zoologique le plus menacé au monde. Mieux connaître, c’est mieux comprendre, ne plus avoir peur et ne plus haïr.

Les varans sont des reptiles fascinants et intelligents. S'ils sont parfois vifs, certains peuvent devenir de calmes compagnons, mais dans tous les cas, ils ont une "personnalité" et un comportement qui laissent rarement indifférents. Selon leur taille ou leurs habitudes, leur élevage diffère. Ce livre a pour but de répondre aux questions principales que se posent la plupart des amateurs qui envisagent de faire l'acquisition de l'un de ces reptiles. Il apporte les connaissances indispensables à l'élevage des principaux varans susceptibles d'être maintenus en terrarium.

Les réponses aux 60 questions que se posent les futurs acheteurs de serpent et les débutants. Très clair : une page = une question et une réponse détaillée. Les grandes thématiques sont toutes abordées : la législation, le matériel, les soins, l'alimentation, le transport, la biologie, les dangers, etc.

Mangrove forests are the dominant intertidal ecosystem of tropical coastlines. In New Caledonia, mangroves act as a buffer zone between Ni open-cast mines and a lagoon registered as a UNESCO World Heritage site. Across the intertidal zone, mangroves are composed of three main stands; with from the seaward side to the landward side: Rhizophora spp., Avicennia marina, salt-flat. This botanical gradient relies on the duration of tidal immersion, which imposes sedimentary gradients of water content, salinity, oxygenation, and organic content.The objective of this PhD thesis was to improve our understanding of the biogeochemistry of iron and nickel in mangrove sediments and to characterize the role of edaphic parameters on trace metals dynamic. Particular emphasis was focused on the mineralogical (bio)transformation of Fe and Ni bearing phases and on crystal chemistry. Both XANES and EXAFS data showed that Fe and Ni speciation strongly followed the redox boundaries marking the intertidal and depth zonations. Fe(III)-bearing goethite and phyllosilicates, herited from lateritic outcrops, were the major Fe and Ni hosts in the upper mangrove sediments. These mineral species were fully preserved at depth in the dry and oxic salt flat area. By contrast, beneath the vegetated Rhizophora and Avicennia stands, goethite rapidly disappeared with depth. In these anoxic horizons, sulfate reduction occurred, and pyrite and organic complexes became the dominant Ni-species. At the limit between oxic and anoxic layers, intense re-oxidation of aqueous Fe(II) and Fe-sulfides led to the formation of ferrihydrite, lepidocrocite and likely goethite. The relative proportion of the newly formed poorly ordered iron-oxyhydroxides was found to be higher in the Rhizophora mangrove stand. Moreover Ni incorporation in pyrite was less developed beneath Rhizophora stand. Such lateral evolution of Ni speciation may be related to reoxidation of Ni-bearing pyrites in the Rhizophora stand, which is subjected to periodic alternation of reducing and oxidizing events due to daily tidal fluctuations. The latter may be a major cause for continuous Fe reduction-oxidation cycles in the vegetated mangrove stands, and could significantly affect iron and nickel mass balances in mangroves. Indeed, Ni was found to be immobile in the salt flat, to accumulate beneath Avicennia and to be partially leached beneath Rhizophora. Eventually, Fe and Ni behavior in mangrove sediments currently oxidizing in response to isolation from the sea, was studied. In the layer of the oxidation front, really high concentrations of dissolved Ni were measured, while Ni concentrations in the solid phase were 4 times lower than in the pyritized horizon, and 2.5 times lower than in the upper sediment. These results suggest that mangrove sediment oxidation was a cause of Ni loss. This PhD thesis allows a better assesment of the mineralogical processes that lead to the fixation or the release of trace metals by mangroves, and is thus useful for the management of mangroves that are situated downstream lateritic watershed.