Lung Ventilation and Temperature Regulation in the European Coot Fulica atra

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Abstract
Consumption of O₂ ( ), production of CO₂ ( ), respiratory frequency (f), tidal volume ( ), total inspired ventilation ( ), body temperature ( ), and expired air temperature ( ) have been measured simultaneously in the coot, Fulica atra (mean body weight 0.398 kg), at ambient air temperatures ( ) ranging from -25 C to 35 C. Below the lower critical temperature (20 C), increased according to the equation (ml O₂ kg⁻¹ min ⁻¹) = 37.52 - 0.97 . At of - 25 Ca ventilation increase of 60% was markedly disproportional to the three- to fivefold increase in . This implies a reduced air convection requirement ( ) of 48%. At of 35 C,fdoubled while remained nearly unchanged. A nearly unchanged associated with the increased at 35 C implies a functional bypass of the parabronchial segments of the lung. Expired air temperature shows a decline nearly parallel to an isothermal line between and . At of - 10 C or lower, was within 2 C of zero. The respiratory responses to changes in are discussed in terms of heat economy, showing that actual respiratory heat loss is only 9.6% of the theoretical maximum at - 25 C. While 79.7% (at- 25 C) can be ascribed to cooling of expired air, 10.7% is due to reduction in .