Ecology, adaptation and acclimatisation mechanisms of Bythograeidae Williams, 1980, a unique endemic hydrothermal vent crabs family: current state of knowledge

Diversified fauna have colonised the deep-sea hydrothermal vents, an environment characterised by high metallic concentrations and sulfide-rich waters. In 1977-79, brachyuran crabs were collected in hydrothermal vents around the Galapagos Rift, allowing description in 1980 of Bythograea thermydron and the new family Bythograeidae (and the superfamily Bythogreoidea). This family has a worldwide distribution and currently includes 13 species classified in 6 genera: Allograea (1 species), Austinograea (3 species), Bythograea (5 species), Cyanagraea (1 species), Gandalfus (2 species) and Segonzacia (1 species). These crabs have distinctive morphological and physiological characteristics, which reflect adaptations to particular deep-sea hydrothermal vent conditions. This review is the first on Bythograeidae, documenting the state of our knowledge regarding their taxonomy, evolution, ecology, morphology and physiology (i.e. osmoregulation, oxygen consumption, sulfide and metal detoxification, temperature tolerance). We also report on recent progress in maintaining bythograeids in an artificial ex situ environment.