A microscopic study of the tracheal epithelium of Testudo graeca and Pseudemys scripta elegans.

The tracheal epithelium of Testudo graeca and Pseudemys scripta elegans was studied by means of light and electron microscopy, histochemistry and immunocytochemistry. Three cell types were detected by conventional light microscopy: mucous, ciliated and basal. The Grimelius silver argyrophil technique was positive in a population of tracheal cells. By immunocytochemistry, serotonin-containing cells were identified. The mucous cells of Testudo graeca contained sialomucins and sulphomucins; however, only sialomucins were detected in Pseudemys scripta elegans. By electron microscopy four cell types were observed: mucous, ciliated, basal and endocrine. Plasma cells were also found. The differences between the species studied lay mainly in the ultrastructure of the ciliated cells, the mucous granules and the presence of a special type of basal cell called 'clear basal cells' in non-hibernating specimens of Testudo graeca. During hibernation, the tracheal epithelium of Testudo graeca showed the following changes: (1) Myelin bodies were present in the cytoplasm. (2) The intercellular spaces were remarkably widened. (3) No 'clear basal cells' were present. In conclusion, the tracheal epithelium of the reptiles studied showed a pattern similar to that described in mammals but some differences from reptiles previously studied were found.