The shivering response during cross-circulation in the common eider duck (Somateria mollissima)

The possible role of humoral factors in the control of shivering in the common eider duck (Somateria mollissima) was investigated using a cross-circulation technique. Pairs of animals were coupled so that the arterial system of one animal was connected to the venous system of the other. The rate of blood transferral was 12.8 ml min-1. By adequate heparinization of the extracorporeal blood supply, cross-circulation could be maintained for periods of up to 12 h. The temperature of blood entering each animal Tinlet) was controlled by heat exchangers. During control experiments Tinlet was maintained at a temperature close to normal body temperature. During cooling experiments Tinlet was maintained at c. 20 degrees C. Changes in metabolic heat production and oesophageal temperature in response to blood cooling were measured in cross-circulated pairs of animals cooled simultaneously or individually. Based on analysis of the metabolic responses under the different experimental situations, no evidence was found to indicate that blood-borne substances are involved in the shivering response in these animals.