Oxygen uptake during early life in the fresh water fish, Esomus danricus (Ham) (Pisces, Cypriniformes)

O2 uptake in Esomus danricus has been determined in relation to body weight, length and thickness of the water-blood diffusion barrier at 27-28 degrees C temperature. Total O2 consumption in larvae was 1311 ml/kg/h but decreased significantly in juvenile fishes (720 ml/kg/h). The increase in the thickness of water-blood diffusion barrier at the secondary gill lamellae of the fish was found to be an important factor for the decrease in VO2. Logarithmic analyses of data for O2 uptake in relation to body weight gave a slope of 0.8865 for larvae and 0.5053 for juveniles. The exponent values of O2 uptake against diffusion barrier for larvae and juveniles were 1.7383 and 2.0956, respectively. The results obtained indicated that fish have an extra device which helps in extracting about 24% of the total VO2 required for the fulfilment of the metabolic oxygen demand of the body.