title: Hemoglobin function in deep-sea and hydrothermal-vent endemic fish: Symenchelis parasitica (Anguillidae) and Thermarces cerberus (Zoarcidae).
abstract: Deep-sea hydrothermal vents probably provide the harshest physico-chemical conditions confronting metazoan animals in nature. Given the absence of information on hemoglobin (Hb) function in hydrothermal-vent vertebrates, and the complex molecular and functional adaptations observed in hydrothermal-vent invertebrates, we investigated the oxygenation reactions of Hbs from the vent-endemic zoarcid Thermarces cerberus and the deep-sea anguillid Symenchelis parasitica from adjacent habitats. Electrophoretically cathodic and anodic isoHbs from S. parasitica exhibit radical differences in O(2) affinity and pH and organic phosphate (ATP) sensitivities, reflecting a division of labor as in other 'class II' fish that express both Hb types. Remarkably, the cathodic Hb (I) lacks chloride sensitivity, and the anodic Hb (II) shows anticooperativity near half-saturation at low temperature. T. cerberus isoHbs exhibit similar affinities and pH sensitivities ('class I' pattern) but much higher O(2) affinities than those observed in Hbs of the temperate, shallow-water zoarcid Zoarces viviparus, which, unless compensated, reveals markedly higher blood O(2) affinities in the former species. The temperature sensitivity of O(2) binding to T. cerberus Hbs and the anodic S. parasitica Hb, which have normal Bohr effects, is decreased by endothermic proton dissociation, which reduces the effects of ambient temperature variations on O(2) affinity. In the cathodic S. parasitica Hb, similar reduction appears to be associated with endothermic conformational changes that accompany the oxygenation reaction.
authors.affiliation: Department of Zoophysiology, C.F. Møllers Alle, Building 131, University of Aarhus, DK 8000 Aarhus C, Denmark. roy.weber@biology.au.dk
authors.forename: Roy E
authors.initials: RE
authors.lastname: Weber
authors.forename: Stephane
authors.initials: S
authors.lastname: Hourdez
authors.forename: Francis
authors.initials: F
authors.lastname: Knowles
authors.forename: Francois
authors.initials: F
authors.lastname: Lallier
mesh_terms: D000222:Adaptation, Physiological; D000811:Anguilla / Q000097:blood / Q000502:physiology*; D000818:Animals; D004777:Environment; D006454:Hemoglobins / Q000502:physiology*; D009792:Oceans and Seas; D010100:Oxygen / Q000097:blood / Q000737:chemistry*; D010473:Perciformes / Q000097:blood / Q000502:physiology*
chemical_list: D006454:Hemoglobins; D010100:Oxygen