Bimodal breathing strategy in Phrynops genus (Wagler, 1830) and Chelus fimbriata (Schneider, 1783)

Abstract

Testudines perform intermittent pulmonary respiration, a convenient process to be less costly energy. Maintaining an intermittent breathing pattern to be advantageous to aquatic turtle that reduce the exposure time to breathe at the surface and thus reduce the time of exposure to predators. This pattern of respiratory rate, with longer intervals apnea, is typical of aquatic life habit of species and may persist even in the terrestrial environment. Some species of aquatic turtles can still perform gas exchange by organs other than the lungs. Gas exchange can occur through the skin of the limbs and / or cloaca, buco-pharyngeal epithelium and / or the cloacal bursa. Phrynops geoffroanus has ventilation and oxygen consumption values much lower when compared to other turtles already investigated. Thus, this study aims to understand the mechanisms of gas exchange in the genre Phrynops and species Chelus fimbriata, testing the hypothesis that animals belonging to such species have extrapulmonary structures able to absorb oxygen and release carbon dioxide into the environment aquatic. In addition, the paper discusses hypothesize that, if documented the presence of extrapulmonary structures of gas exchange for the two genders, this result may mean a morphophysiological phylogenetic signal. (AU)