- 1) Dept. of Physiology, Faculty of Medicine, University of Khartoum, Sudan
- 2) Dept. of Zoology, Faculty of Science, University of Khartoum, Sudan
1. The oxygen consumption by the tropical species, Tilapia nilotica, has been investigated. 2. A direct relation between oxygen consumption and the concentration of oxygen in water was found. The consumption was high when the concentration of oxygen was above critical levels. This, however, dropped when the oxygen was below critical levels (2.5–3 mg/l) as shown by figs. 2,3 and Table I. 3. Irrespective of the activity of the fish, when the oxygen content of water was below critical levels, the consumption remained quite low. Therefore, the high consumption at the beginning of the experiments could not be attributed or related to activity alone as previous workers suggested for other species. 4. The difference in oxygen consumption by fishes of different weights was only significant at high concentrations. At low oxygen levels (1.0 mg/1) the difference in consumption became inconspicuous. 5. It was concluded that the respiratory surface might be inadequate for the diffusion of oxygen at levels below critical. The ability of the fish to survive in very low oxygen concentrations is an adaptation of ecological significance as Tilapia nilotica inhabits tropical waters that are subjected to marked oxygen deficiency.
- 1 - sciences appliquees, technologies et medecines
- 2 - sciences biologiques et medicales
- 3 - sciences biologiques fondamentales et appliquees. psychologie