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Étude et protection des gallaselles et de leurs habitats aquatiques souterrains en Poitou-Charentes

Abstract : A stratified sampling of 129 sites in the region Poitou-Charentes (central-western France), covering the 4 departments, the 4 recognized types of aquifers, and the 5 major watersheds, allowed to make the first inventory of local stygobites (or stygofauna, i.e., all invertebrates living in the subterranean aquatic environment, such as underground rivers, phreatic waters, springs or sub-flows of rivers). The Gallaselle (Gallasellus heilyi), a small endemic crustacean for which the region has a strong responsibility, was contacted on 23 new sites, bringing to 31 the total number of known localities (since its discovery in 1955). Its range thus expanded considerably to the north up to northern Marais poitevin, and to the south up to the watershed of the Garonne River. In fact, morphological and genetic analyzes conducted in parallel tend to reveal the existence not only of one species but several species of gallaselles. Experiments conducted in the laboratory (populations of Vienne and Deux-Sèvres departments) highlighted the importance of biofilms (gelatinous layer of micro-organisms) in the diet of gallaselles, and revealed their basal trophic position in the subterranean hydro-systems. Their main habitat seems to be the large water bodies of karstic and fractured aquifers from the Jurassic and Cretaceous period (Secondary era). The physico-chemical analysis of water did not highlight particular polluo-sensitivity, if not a certain tolerance to the nitrates. The inventory of the associated stygofauna identified a minimum 30 taxa (half crustaceans but also molluscs, annelids and arachnids), most locally unknown, and some possibly new for Science. The lack of taxonomic resolution, among others reasons, do not allow at this stage using stygobites and stygo-fauna as bio-indicators of groundwater quality (although it remains to be investigated further). At the end of this study, taking into account the biodiversity inventoried (Gallasellus spp. and other noteworthy stygobites) and the potentiality in terms of communication, 4 hydro-geologic areas are suggested to protection (one per department), including 3 in the watershed of the Charente River, the backbone of the Region, which concentrates nearly half of the known populations: • the fountain and underground aqueducts of Tusson (Charente department); • the micro-watershed of the underground river of Bataillé (Deux-Sèvres department); • the micro-watershed of the Ruisseau du Roi (Charente-Maritime department); • the micro-watershed of the Ruisseau des Dames (Vienne department).
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Submitted on : Friday, September 23, 2016 - 11:59:08 AM
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François Lefebvre, Bruno Fillon, Gailledrat Miguel. Étude et protection des gallaselles et de leurs habitats aquatiques souterrains en Poitou-Charentes. [Rapport de recherche] Poitou-Charentes Nature. 2016, pp.90. ⟨hal-01350900⟩

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