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  • Articles  (2)
  • Clarias  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Aspects of the biology of the catfish Clarias lazera (Cuv. & Val.) related to its economic cultivation (1984)
    Springer
    Hydrobiologia 110 (1984), S. 295-304 
    Details
    ISSN: 1573-5117
    Keywords: Sudan ; Clarias ; breeding ; maturation ; hormones ; growth ; cultivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The seasonal abundance, population structure, reproduction, feeding, respiratory adaptations and tolerance were studied in the catfish Clarias lazera (Cuv. & Val.) in the reservoir of Jebel Aulia on the White Nile, and in the Green-Belt canals near Khartoum. Continuous monitoring of the ripe, spent and spawning females and immature fish in the population revealed that C. lazera breed synchronously in the autumn in the reservoir and rather sporadically in the canals. Medium-sized females were more fecund than old and young females. Administration of pituitary extract enhanced maturation, induced spawning in mature fish, stimulated body growth, especially in maturing specimens, and produced, as a side-effect, a diuretic response. Mature fish depended on pulmonary respiration for about 45% of the total oxygen requirement. C. lazera fed preferentially on its fry and on decayed proteinaceous food. The suitability of this species for economic cultivation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025801
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  • 2
    Electronic Resource
    Electronic Resource
    Adaptive respiratory significance of organophosphates (ATP & GTP) in air-breathing fishes (1984)
    Springer
    Hydrobiologia 110 (1984), S. 339-349 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00025807
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    Paper (German National Licenses)
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