title: Hydromineral regulation in the hydrothermal vent crab Bythograea thermydron.
abstract: This study investigates the salinity tolerance and the pattern of osmotic and ionic regulation of Bythograea thermydron Williams, 1980, a brachyuran crab endemic to the deep-sea hydrothermal vent habitat. Salinities of 33 per thousand-35 per thousand were measured in the seawater surrounding the captured specimens. B. thermydron is a marine stenohaline osmoconformer, which tolerates salinities ranging between about 31 per thousand and 42 per thousand. The time of osmotic adaptation after a sudden decrease in external salinity is about 15-24 h, which is relatively short for a brachyuran crab. In the range of tolerable salinities, it exhibits an iso-osmotic regulation, which is not affected by changes in hydrostatic pressure, and an iso-ionic regulation for Na(+) and Cl(-). The hemolymph Ca(2+) concentration is slightly hyper-regulated, K(+) concentration is slightly hyper-hypo-regulated, and Mg(2+) concentration is strongly hypo-regulated. These findings probably reflect a high permeability of the teguments to water and ions. In addition to limited information about salinity around hydrothermal vents, these results lead to the hypothesis that B. thermydron lives in a habitat of stable seawater salinity. The osmoconformity of this species is briefly discussed in relation to its potential phylogeny.
authors.affiliation: Laboratoire d'Ecophysiologie des Invertébrés, EA 3009 Adaptation Ecophysiologique au cours de l'Ontogenèse, Université Montpellier II, Pl E. Bataillon, 34095 Montpellier cedex 05, France.
authors.forename: A S
authors.initials: AS
authors.lastname: Martinez
authors.forename: J Y
authors.initials: JY
authors.lastname: Toullec
authors.forename: B
authors.initials: B
authors.lastname: Shillito
authors.forename: M
authors.initials: M
authors.lastname: Charmantier-Daures
authors.forename: G
authors.initials: G
authors.lastname: Charmantier
mesh_terms: D000818:Animals; D003386:Brachyura / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism / Q000502:physiology*; D006458:Hemolymph / Q000737:chemistry; D010140:Pacific Ocean; D012964:Sodium / Q000378:metabolism / Q000502:physiology*; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D002712:Chlorides; D012964:Sodium