Morphology and Glycan Composition of the Mandibular Glands in the White‐Eared Opossum (Didelphis albiventris)

The white‐eared opossum, Didelphis albiventris , is an opportunistic and omnivorous marsupial, whose diet ranges from wild fruits to eggs and birds. Salivary glycoproteins play a key role in the protection of the oral cavity and the formation of the food bolus. Despite the importance of salivary glycoproteins, their detailed investigation in the white‐eared is lacking. This study investigated the morphology and glycan composition of the mandibular salivary glands of the white‐eared opossum for the first time. Histological and histochemical investigations were conducted on tissue fragments fixed with 4% PBS‐buffered paraformaldehyde and embedded in Paraplast. The pattern of glycoproteins was investigated using traditional histochemical methods (PAS, Alcian Blue pH 2.5, and High‐Iron Diamine staining) and lectin histochemistry. The glandular parenchyma consisted of acinar secretory units and a duct system characterized by abundant striated ducts. Secretory acini secrete neutral glycans and non‐sulfated acid glycans. Mannosylated N‐linked glycans terminating in α2,6‐sialic acid and fucose are expressed in the secretory acini, containing intraluminal α2,3‐sialylated O‐linked glycans. The epithelial lining of the striated and interlobular ducts also shows O‐linked glycans with terminal Galβ1, 3GalNAc, and α GalNAc residues. Finally, the epithelium and lumen of interlobular ducts are enriched with additional GalNAc‐terminated O‐linked glycans with the appearance of lactosaminated glycans and the disappearance of α2,3‐sialylated glycans. These results suggest that the saliva produced by the mandibular gland of the white‐eared opossum consists of a species‐specific pattern of glycoproteins, to whose composition the ductal system also contributes. The observed glycan composition is probably related to the diet of the white‐eared opossum and its adaptations to the environment and food availability. These results indicate that the mandibular salivary gland of the white‐eared opossum Didelphis albiventris has specific histological and molecular characteristics compared to other marsupial species, suggesting that diet and habitat, but not the taxonomic group, influence the mandibular gland features.