The effects of temperature on oxygen uptake, gill ventilation and ECG waveforms in the Nile tilapia, Oreochromis niloticus

Oreochromis niloticus were acclimated to 35 (group I) and 15 degrees C (group II). In group I, the temperature was decreased from 35 to 15 degrees C, followed by return to 35 degrees C, while iq group II, the temperature rose to 35 and returned to 15 degrees C. For each temperature, oxygen uptake ((V) over dot O-2), gill ventilation ((V) over dot (G)) and electrocardiograms were obtained. Curves were identical and for the two groups were without hysteresis. Increases of (V) over dot (G)/(V) over dot O-2 with rising temperature kept O-2 extraction relatively constant. Heart rate increased with temperature. The QRS and the T wave amplitudes were constant, while QRS and ventricular action potential duration increased at low temperature. (C) 1998 Elsevier Science Ltd. All rights reserved.