Evolução do sistema respiratório em Squamata

The Squamata group exhibits remarkable diversity in pulmonary structure, including unicameral, paucicameral, and multicameral lungs, reflecting a complex evolutionary history that remains incompletely understood. Although the pulmonary morphology of non-avian reptiles, such as Squamata, has been extensively studied, the evolutionary implications of these variations are still unclear. Given the currently accepted phylogenies for the group, this structural diversity prompted an in-depth investigation into the evolution of the respiratory system in Squamata. In this study, we conducted a comprehensive compilation of pulmonary morphological data, followed by comparative phylogenetic analyses to reconstruct the evolution of these traits within the group (Chapter 1). The results revealed a strong phylogenetic signal across all variables tested, suggesting a close association between pulmonary characteristics and the evolutionary history of Squamata. Despite uncertainties regarding the ancestral lung of Amniotes, the data indicate a high probability of a unicameral lung at the base of Squamata. In the case of Serpentes, the analysis showed that the loss of the tracheal lung and the reduction of the left lung occurred more frequently than the acquisition or development of these organs, although there remain uncertainties about the hypothetical ancestral state of these features within the group. To understand the development of these structures in Squamata, we conducted studies on specimens at different embryonic stages (Chapter 2). The results did not indicate the presence of multicamerality during pulmonary development in the group. This dissertation provides valuable insights into the evolution and development of the respiratory system in Squamata, highlighting the complexities and morphological patterns that characterize the group.