Benthic Ecogeochemistry Laboratory
UMR 8222

PhD student: Victor Le Layec, Thesis director : Stéphane Hourdez
Thesis defended

The Polynoidae (polychaeteous annelids) are found in all marine environments: in polar, temperate and tropical environments, and in coast areas, as well as in the great abyssal depths, including at deep hydrothermal vents and cold seeps. This diversity of habitats and the great number of specie represent a very good opportunity for comparative approaches to study adaptation in a controlled phylogenetic context. If all known species possess neuroglobin, only hydrothermal ones have hemoglobin circulating freely within their coelomic fluid. These hemoglobins exhibit a diversity of structures (tetradomaine or single-domain subunits) and a diversity of properties. The hemoglobins possess a high affinity for oxygen, which allows polynoids to extract oxygen from the environment, even when environmental concentrations are very low. This capacity allows hydrothermal vent species to maintain a stable oxygen consumption rate at low environmental concentrations (oxyregulators) while littoral species are oxyconformers. The presence of hemoglobin also represents an oxygen storage allowing the polynoids to withstand periods of anoxia experienced near deep-sea hydrothermal vents. They also likely play a role in the physiological temperature tolerance of hydrothermal species by allowing sufficient oxygen supply to meet the temperature-related increase in metabolism.