Patterns of Nitrogen Excretion and Oxygen Consumption During Ontogenesis of Common Carp (Cyprinus carpio)

By monitoring nitrogen (ammonia and urea) excretion and oxygen consumption in a continuous manner during early development (from 18 to 350 degree days) of common carp, Cyprinus carpio, we noted high rates of ammonia-N excretion (> 100 and > 50 μgN∙h−1∙103 eggs−1) and of oxygen consumption (> 1 and > 2.5 mg∙h−1∙103 eggs−1) at hatching and at the onset of free-swimming stages, respectively. There was a diurnal rhythm in metabolic activity. The relative proportions of urea-N and ammonia-N varied during early development; the mean urea-N excretion rate amounted to 21.9 ± 8.7% of total nitrogen, and there was no significant difference between embryonic and postembryonic stages. Fasted free-swimming larvae exhibited increased metabolic activity just before the onset of massive mortality (> 75 μg N∙h−1∙103 eggs−1 and > 2 mg O2∙h−1∙103 eggs−1 of nitrogen excretion and oxygen consumption, respectively). Ammonia excretion rates increased with temperature, the Q10's being 2.36, 2.33, and 3.53 during embryonic, hatching, and free-swimming stages, respectively.Key words: carp, ontogenesis, nitrogen excretion, ammonia, urea, oxygen consumption, temperature, diurnal rhythm