Sistema respiratório de Amphisbaena vermicularis e Amphisbaena microcephala (Squamata, Amphisbaenia, Amphisbaenidae)

Abstract

ABSTRACT. Respiratory system of Amphisbaena vermicularis and Amphisbaena microcephala (Squamata, Amphisbaenia, Amphisbaenidae). The macroscopic and microscopic morphology of the trachea and lungs of Amphisbaena vermicularis Wagler, 1824 and Amphisbaena microcephala (Wagler, 1824), as well as the ultrastructure of the pulmonary respiratory chambers of the latter, are described for the first time. The trachea does not ramify, and its caudal segment, between the lungs, was named bronchus. The left lung is long, sac-like and unicameral, with a faveolar parenchyma in the cranial portion and a trabecular parenchyma in the caudal portion. Respiratory chambers are present in both regions of the lungs and it is suggested that the caudal portion acts as a reservoir of air. The right lung is reduced in both species, however in A. vermicularis this reduction is fairly pronounced and only a vestige of this organ can be observed, but in A. microcephala the right lung is a delimited organ that links to the caudal portion of the tracheal tube through two holes. Pneumocytes I and II occur in the respiratory chambers. The basal membranes of the pneumocytes I and of the endothelial cells are fused, diminishing the air-to-blood barrier which measures approximately 0.5 µm in A. microcephala. Morphological features described in this paper may represent some adaptations that permit the survival of the specimens of Amphisbaenia in the subterranean galleries where they spend most of their lives, under conditions of low air renewal, relatively variable levels of humidity and suspended particles.