ADAPTATIONS TO CHRONIC HYPOXIA IN POLYCHAETES FROM HYDROTHERMAL VENTS AND COLD-SEEPS

Polychaetes living near hydrothermal vents and cold-seeps can be exposed to severe hypoxia. Studies of polychaetes from hydrothermal vents (alvinellids and polynoids) and from cold-seeps (orbiniid) revealed several anatomical and physiological adaptations to hypoxia. All the species, compared to littoral species, exhibit increased specific gill surface area. This is particularly significant for polynoids, which are usually devoid of gills. Reduced diffusion distances at the level of the gill probably also facilitate oxygen uptake. All the species studied possess hemoglobin, increasing the oxyphoric capacity of the body fluids. Hemoglobin could also be a storage of oxygen for periods of hypoxia and anoxia. These hemoglobins have been studied in Alvinella pompejana and Branchipolynoe symmytilida and exhibit a very high affinity and a strong Bohr effect.