Adaptations respiratoires des annélides polychètes de milieux abyssaux hypoxiques

Abstract : The animals living near hydrothermal vents and cold-seeps experience environmental conditions which are challenging for respiration (little oxygen, presence of large amounts of sulfide and carbon dioxide ). We used polychaetes from these two environments: Alvinella pompejana, from the hot part of the hydrothermal vent ecosystem, Branchipolynoe spp., commensal with the mussels found in the cold part of hydrothermal vents and an orbiniid from the Gulf of Mexico cold-seeps. We investigated the anatomical and physiological adaptations facilitating gas exchange in these three species. The anatomical adaptations are an increase of the gill surface area and a decrease of the diffusion distance at the level of these gas exchange organs. Branchipolynoe is unusual in having gills, an anatomical feature lacking in littoral species of the same family. These gills are perfused by the coelomic fluid instead of the blood as in the other species. In the orbiniid, most of the gas exchanges take place in the anterior part of the body. The three species possess hemoglobin, another feature distinguishing Branchipolynoe from the littoral polynoids. While the two other species exhibit typical annelid hemoglobins, the coelomic hemoglobins of Branchipolynoe are very unusual: they are dimers and trimers of tetradomain globins. The body fluids of A. pompejana and Branchipolynoe are able to buffer the effects of the variations of carbon dioxide concentration. All the the species studied possess hemoglobins with very high oxygen affinities, allowing a good extraction of the oxygen from their hypoxic environment. In A. pompejana, there is an internal gas transfer system allowing the worm to store oxygen when the conditions are good and to release it into the vascular system when its environmental concentration is too low.
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  • HAL Id : tel-01115532, version 1

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Stéphane Hourdez. Adaptations respiratoires des annélides polychètes de milieux abyssaux hypoxiques. Ecologie, Environnement. Paris 6, 2000. Français. ⟨tel-01115532⟩

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