title: Ionoregulatory Aspects of the Osmorespiratory Compromise during Acute Environmental Hypoxia in 12 Tropical and Temperate Teleosts.
abstract: In the traditional osmorespiratory compromise, as seen in the hypoxia-intolerant freshwater rainbow trout (Oncorhynchus mykiss), the branchial modifications that occur to improve O2 uptake during hypoxia result in unfavorable increases in the fluxes of ions and water. However, at least one hypoxia-tolerant freshwater species, the Amazonian oscar (Astronotus ocellatus), shows exactly the opposite: decreased branchial flux rates of ions, water, and nitrogenous wastes during acute hypoxia. In order to find out whether the two strategies were widespread, we used a standard 2-h normoxia, 2-h hypoxia (20%-30% saturation), 2-h normoxic recovery protocol to survey 10 other phylogenetically diverse tropical and temperate species. Unidirectional influx and efflux rates of Na(+) and net flux rates of K(+), ammonia, and urea-N were measured. The flux reduction strategy was seen only in one additional species, the Amazonian tambaqui (Colossoma macropomum), which is similarly hypoxia tolerant and lives in the same ion-poor waters as the oscar. However, five other species exhibited evidence of the increased flux rates typical of the traditional osmorespiratory compromise in the trout: the rosaceu tetra (Hyphessobrycon bentosi rosaceus), the moenkhausia tetra (Moenkhausia diktyota), the bluegill sunfish (Lepomis macrochirus), the zebra fish (Danio rerio), and the goldfish (Carassius auratus). Four other species exhibited no marked flux changes during hypoxia: the cardinal tetra (Paracheirodon axelrodi), the hemigrammus tetra (Hemigrammus rhodostomus), the pumpkinseed sunfish (Lepomis gibbosus), and the Atlantic killifish (Fundulus heteroclitus). Overall, a diversity of strategies exist; we speculate that these may be linked to differences in habitat and/or lifestyle.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada; 2Instituto Nacional de Pesquisas da Amazônia, Laboratório de Ecofisiologia e Evolução Molecular, Manaus, Amazonas CEP 68080-971, Brazil; 3Rosenstiel School of Marine and Atmospheric Science, University of Miami, Florida 33149, and Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Robertson
authors.forename: Adalberto Luis
authors.initials: AL
authors.lastname: Val
authors.forename: Vera F
authors.initials: VF
authors.lastname: Almeida-Val
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
mesh_terms: D000222:Adaptation, Physiological; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D005399:Fishes / Q000378:metabolism*; D064587:Osmoregulation; D010100:Oxygen / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012119:Respiration; D012964:Sodium / Q000378:metabolism; D013045:Species Specificity; D014508:Urea / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water; D000641:Ammonia; D014508:Urea; D012964:Sodium; D011188:Potassium; D010100:Oxygen