title: Environmental modulation of the onset of air breathing and survival of Betta splendens and Trichopodus trichopterus.
abstract: The effect of hypoxia on air-breathing onset and survival was determined in larvae of the air-breathing fishes, the three spot gourami Trichopodus trichopterus and the Siamese fighting fish Betta splendens. Larvae were exposed continuously or intermittently (12 h nightly) to an oxygen partial pressure (PO2 ) of 20, 17 and 14 kPa from 1 to 40 days post-fertilization (dpf). Survival and onset of air breathing were measured daily. Continuous normoxic conditions produced a larval survival rate of 65-75% for B. splendens and 15-30% for T. trichopterus, but all larvae of both species died at 9 dpf in continuous hypoxia conditions. Larvae under intermittent (nocturnal) hypoxia showed a 15% elevated survival rate in both species. The same conditions altered the onset of air breathing, advancing onset by 4 days in B. splendens and delaying onset by 9 days in T. trichopterus. These interspecific differences were attributed to air-breathing characteristics: B. splendens was a non-obligatory air breather after 36 dpf, whereas T. trichopterus was an obligatory air breather after 32 dpf.
authors: University of North Texas, Department of Biological Sciences, Denton, TX 76203, U.S.A.; Departamento de Biología, Universidad Autónoma del Estado de México, Instituto Literario 100, Centro, Toluca, Estado de México 50120, México.
authors: J F
authors: JF
authors: Mendez-Sanchez
authors: W W
authors: WW
authors: Burggren
mesh_terms: D000222:Adaptation, Physiological; D000388:Air; D000818:Animals; D004777:Environment; D000860:Hypoxia; D007814:Larva / Q000502:physiology; D010100:Oxygen / Q000032:analysis; D010473:Perciformes / Q000502:physiology*; D010641:Phenotype; D012119:Respiration
chemical_list: D010100:Oxygen
keywords: developmental plasticity; heterokairy; hypoxia