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  • Polypterus  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 110 (1984), S. 339-349 
    ISSN: 1573-5117
    Keywords: Sudan ; Protopterus ; Polypterus ; Clarias ; ATP ; GTP ; development ; hypoxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ATP and GTP contents of erythrocytes of Protopterus annectens, Polypterus senegalus and Clarias lazera were assessed in relation to maturation and hypoxia. The steady state ‘normal’ concentrations of ATP were: 446, 316 and 475 µM/100 ml and those of GTP were 286, 93 and 85 µM/100 ml in Protopterus, Polypterus and Clarias, respectively. The level of ATP decreased and that of GTP increased with increments in body growth, especially during development of the pulmonary organs. The concentration of GTP also increased progressively with hypoxia (O2: 7.4 to 3.6 mg/l); the level ATP remained almost unaltered. The ratio of GTP increased markedly with increased hypoxia particularly in the adaptive respiratory range of aquatic oxygen concentrations (6.5–4.8 mg/l) when the fish were forced to depart from branchial respiration and became reliant on air-breathing.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 110 (1984), S. 351-363 
    ISSN: 1573-5117
    Keywords: Sudan ; Polypterus ; aerial ; branchial ; respiration ; hypoxia ; hypercarbia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The respiratory behaviour and partitioning of O2 uptake between air and water were investigated in Polypterus genegalus using continuous-flow and two-phase respirometers and lung gas replacement techniques P. senegalus rarely resorts to aerial respiration under normal conditions. Partitioning of O2 consumption depends on the activity and age of fish and the availability of aquatic oxygen. Immature fish (12–22 g) cannot utilize aerial O2 but older fish exhibit age-dependent reliance on aerial respiration in hypoxic and hypercarbic waters. Pulmonary respiration accounts for 50% of the total requirement at aquatic O2 concentrations of about 3.5 mg · l−1 (or CO2 of about 5%) and fish rely exclusively on aerial respiration at O2 concentrations of less than 2.5 mg · l−1. Branchial respiration is initially stimulated by hypercarbia (CO2: 0.5–0.8%) but increased hypercarbia (CO2 − 1%) greatly depresses (by over 90%) brancial respiration and initiates (CO2: 0.5%) and sustains pulmonary respiration.
    Type of Medium: Electronic Resource
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