Urea and ammonia excretion by embryos and larvae of the African catfish
Clarias gariepinus (Burchell 1822) |
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Authors: | BF Terjesen J Verreth HJ Fyhn |
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Institution: | (1) Zoological Institute, University of Bergen, Allégt. 41, N-5007 Bergen, Norway;(2) Department of Fish Culture and Fisheries, Wageningen Agricultural University, P.O. Box 338, 6700 AH Wageningen, The Netherlands |
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Abstract: | Yolk-sac larvae and starved larvae of Clarias gariepinus (Burchell 1822), reared at 28°C, were predominantly ammonotelic, but urea excretion contributed about 19±7% to the total nitrogen excretion. Exogenously feeding larvae of C. gariepinus were mainly ammonotelic until 180-205 h post fertilization, but from then on the relative urea excretion stabilized at 44±13%. The contents of total free amino acids (FAA) and ammonia in C. gariepinus peaked around complete yolk absorption. During the first period after hatching 64% of the FAA and 60% of the total ammonia were located in the yolk compartment. The body compartment contained the highest amount of FAA and total ammonia at the end of the yolk-sac period (65 and 77%, respectively). The amount of nitrogen originating from catabolism of amino acids was balanced within 6% by the excreted sum of ammonia and urea. The high degree of ureotelism in C. gariepinus larvae may constitute an adaptive mechanism to a habitat of temporal water shortage. |
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Keywords: | Clarias gariepinus embryos larvae urea ammonia excretion accumulation free amino acids protein |
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