The uropygial gland of the monk parakeet Myiopsitta monachus: histology, morphogenesis and evolution within Psittaciformes (Aves)

CARRIL J,; CHIALE MC; BARBEITO CG.

EVOLUTION & DEVELOPMENT

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020 vol. 22 p. 269 - 282

1520-541X

We describe the morphology, histology, and histochemical characteristicsof the uropygial gland (UG) of the monk parakeet Myiopsitta monachus.The UG has a heart-shape external appearance and adenomersextensively branched with a convoluted path, covered by a stratifiedepithelium formed by different cellular strata and divided into threezones (based on the epithelial height and lumen width), a cylindricalpapilla with an internal structure of delicate type and two excretorypores surrounded by a feather tuft. Histochemical and lectinhistochemicaltechniques performed showed positivity against PAS, ABpH 2.5, AB-PAS and some lectines, likely related to the granivorousfeeding habits. Also, we describe the morphogenesis of the UG of themonk parakeet, which appears at embryological stage 34 as a pair ofectodermal invaginations. Heterochronic events in the onsetdevelopment of the UG when compared with other birds could berecognized. Finally, to examine the phylogenetic occurrence of the UGwithin the Psittaciformes and infer its evolutionary history, we mappedits presence/absence over a molecular phylogeny. The reconstruction ofthe characters states at ancestral nodes revealed that the presence ofthe UG was the plesiomorphic feature for Psittaciformes and its lossevolved independently more than once.