Lectin histochemistry of salivary glands in the Gian t An t-eater (Myrmecophaga tridactyla)

Abstract

The submandibular and buccal glands of the Giant Ant-eater (Myrmecophaga tridactyla) have been studied by means of a series of carbohydrate histochemical methods, including a broad spectrum of PO-lectin procedures. The seromucous cells (Gl. submandibularis) and mucous cells (Gl. buccalis) of the glandular acini, as well as the secretion in the excretory duct system exhibited very strong to strong reactions for neutral and acidic glycocongugates. The serous cells of the buccal glands and the excretory duct cells reacted rather weakly. The different controls applied particularly emphasized that sialoglycoconjugates are the predominant ingredients of the saliva secreted. Lectin histochemical differentiation demonstrated a varying pattern of saccharide residues in these substances. In the submandibular glands the glycocongujates (mostly proteoglycans) of the seromucous cells and the luminal secretion normally contained terminal B-galactose and minor contents of terminal a-N-acetylglucosamine. After sialidase digestion this cell type exhibited distinct amounts of sialic acid-B-galactose and sialic acid-a-N-acetylgalactosamine. Sialic acid was also clearly present in the tough interlobular connective tissue. The buccal glands showed a similar distribution of saccharide residues in the mucous cells. In the serous cells, however, acidic glycoproteins with sialyl residues were observed, also containing terminal a-D-mannosyl, a-N-acetylgalactosaminyl, and B-D-galactosyl residues. The cells of the excretory duct system of both gland types reacted weakly to moderately for terminal sugar residues (Nacetyl- D-glucosamine, N-acetyl-D-galactosamine, B-Dgalactose). The results obtained are discussed in view of the specific feeding mode of the Giant Ant-eater, whereby high contents of sialoglycoconjugates (proteoglycans, glycoproteins) produced by the salivary glands warrant for the main function of the non-sticky saliva; i.e., to act as an effective lubricant during tongue movement.