A comparison of ventilation rates and haemoglobin concentrations between two species of loach,Noemacheilus barbatulus (L.) and Cobitis taenia (L.)

The mean haemoglobin concentration of Noemacheilus barbatulus was found to be significantly higher than that of Cobitis taenia. Under conditions of reduced oxygen saturation, both species achieved maximum rates of ventilation at 10% 0₂. An alteration in opercular beat pattern accounted for the increased ventilation rates between 20% and 30%. A slightly higher tolerance for lowered oxygen concentrations was demonstrated by Cobitis taenia with disorientation and aerial respiration occurring at lower oxygen tensions than in Noemacheilus barbatulus.