Abstract
To prove air breathing, common carps Cyprinus carpio acclimated at 27°C were subjected to the following experiments after a 3 h precooling period in water by decreasing the temperature to 17°C. 1) Each fish with a plugged oesophagus was accommodated in a respiratory chamber connected to gas meters for measurements of concentration changes of O2 and CO2 at 17°C. 2) Each group of five fish was exposed to 17°C air to examine its 100% survival time.
Over time, the O2 concentration decreased and that of CO2 increased. The CO2 concentration showed a saturation curve. Mean respiratory rates in the initial period of 1-1.5 h were 51±24.2ml O2 per kg•h and 24±5.8ml CO2 per kg•h. The 100% survival time with a 3 h precooling was 4.5 h. As a conclusion, carp breathe following an incomplete CO2 excretion even in air.
