ABSTRACT
The sarcopterygian fish gave rise to the lungfish, the coelacanths and the land vertebrates. The South American lungfish feeds on mollusks and other invertebrates but may also eat vegetables. Like in amphibians, the mechanics of pulmonary ventilation in lungfish is based on positive pressure inflation of the lung. An intriguing problem is the function of gills in extant lungfish, in particular in Lepidosiren, which has a negligible surface. Aestivation is a dormancy that may occur during the dry season. In this condition, metabolism can be reduced without any decrease of ambient temperature. The lungfish very likely originated from the sister group of the land vertebrates and, therefore, it is not surprising that they share many features of respiratory control with the amphibians. The Lepidosireniformes and anuran amphibians are distinctly different as to set points for blood gases. In Lepidosiren the gill system that accounts for less than 0.1% of the total respiratory surface.
