| Summary |
Light and electron microscopy techniques were used to examine the pulmonary structural details of Notophthalmus viridescens viridescens. Possible hydrostatic function of the lungs for the adult newt was also examined by removing lungs from adult newts. The trachea and lungs of adults and juveniles were characterized. Stains used to differentiate tissues and identify possible mucosubstances included the Mallory triple stain, PAS stain, Alcian blue stain, Orcein elastin stain, and lectin histochemistry. The lectins used were GSA 1-B4, WGA, DBA, PNA, UEA-1, and LTA. The possible effects of exogenous prolactin on lung morphology were examined. Serial sectioning revealed that the trachea contains pseudostratified columnar ciliated epithelium and cuboidal to columnar epithelium; the trachea is strengthened in its lateral walls by two horseshoe-shaped rings of hyaline cartilage that extend into two short bronchi. The bronchi precede two thin, translucent, elongate lungs without any septation. Vascularization consisted of a pulmonary artery and vein, both of which extend the length of the lung with smaller vessels branching off at right angles. The lungs contained a pseudostratified columnar ciliated epithelium associated only with the pulmonary vein and simple cuboidal to columnar epithelium elsewhere. The underlying connective tissue consists of a dense network of collagen fibers, elastic fibers, and scattered fibroblast-type nuclei. Examination by transmission electron microscopy revealed numerous capillary loops that form loops on the respiratory surface of the lung and are covered by a thin squamous epithelium. Examination of the trachea and the lungs of the red eft revealed an acidic mucopolysaccharide substance found in association with the ciliated cells; this material is believed to be a surfactant-type material. Exogenous prolactin did not have any gross effects on lung morphology or on the occurrence or distribution of glycoconjugates in lung tissue. However, the lung morphology may change seasonally or in response to varying environmental conditions. Adult newts are probably facultative air-breathers; adults survived up to seven days following lung removal which provides evidence that adult newts may respire largely by cutaneous respiration. Newts with removed lungs were unable to float, supporting the view that lungs may serve a hydrostatic function. |
