Histochemical and immunohistochemical adaptations on the gastroesophageal tube of the blue‐fronted parrot (Amazona aestiva  Linnaeus, 1758)

Abstract

Amazona aestiva Linnaeus, 1758 is known as the blue‐fronted parrot. These animals are considered seed dispersion, contributing to ecological balance. Despite its ecological importance, A. aestiva is listed as an imminent danger of becoming extinct, as it is one of the most illegally traded native species in Brazil, besides losing its habitat due to deforestation and forest fires. The cranial oesophagus mucosa is lined with a non‐keratinized stratified squamous epithelium, and the basal layer presents melanocyte accumulation. No mucous glands were observed in the lamina propria/submucosa. The ingluvium two different muscular layer patterns were observed, one internal and circular and one very thick, external and longitudinal. The proventriculum submucosa consists of polygonal proventricular glands and contents into a broad central duct lined with simple columnar epithelium Periodic acid‐reactive Schiff positive (PAS+) and Alcian blue positive (AB+). The 5‐HT cells are dispersed in the proventricular glands located at base and apex. The ventricle mucous layer contains numerous branched folds lined by a simple columnar epithelium. The epithelium was negative reaction for PAS and positive for AB only on the fold surfaces. The 5‐HT cells were scarce and observed only at the base of the ventricular gland, as well as in the adjacent connective tissue.