Histochemical study of Magellanic penguin (Spheniscus magellanicus) minor salivary glands during postnatal growth

Abstract

The histological and histochemical features of the minor salivary glands during postnatal development have been generally associated with the type of food ingested. However, recent studies support the fact that these salivary glands develop independently of the diet; in fact, minor salivary glands have similar morphological and histochemical characteristics in adult individuals of species with different diet regimens. Thus, the aim of this study was to characterize the developmental morphology of the penguin minor salivary glands and to contrast them with minor salivary glands of other species. The tongue, palatine, and mouth cavity (bottom) minor salivary glands of newborn, 1- to 20-day-old, and adult magellanic penguins were studied with hematoxylin-eosin, periodic acid-Schiff, alcian blue, toluidine blue, and lectin histochemistry. Minor salivary glands were present at all ages, although they were only moderately developed in animals less than 15 days old. After this age, glands were abundant in all age groups; in addition, cells from the glandular epithelium were functionally mature and secreted mucins. Nevertheless, in newborn to 15-day-old penguins, mucins were located only at the apical cytoplasm of mucous cells. In all ages, mucous cells displayed periodic acid-Schiff-positive, alcianophilic, and metachromatic reactions; among mucous cells, other orthochromatic cells appeared interspersed. From 15 days on, histochemical reactions became more intense until adulthood, and the cytoplasm of secretory cells was filled with glycoproteins and sulfomucins. Moreover, lectins bound to different oligosaccharides in mucous cells, depending on the stage of maturation of the glands. In conclusion, penguin minor salivary glands are already present at birth, and show progressive and quantitative increases in mucous secretion during postnatal development. These changes are necessary not only for nutrient ingestion, but also for nonimmune protection of the buccal cavity.

<b>Ultrastructural aspects of the tongue in Magellanic Penguins <i>Spheniscus magellanicus</i> (Forster, 1781)

“…This characteristics was also observed by Oliveira et al (2011) in Spheniscus magllanicus and Kobayashi et al (1998) in other four species of penguins: Spheniscus demersus, Pygoscelis papua, Spheniscus humboldti, and Eudyptes chrysolophus. The triangular shape with the pointed apex is considered the standard in omnivorous birds (GARDNER, 1927).…”

“…However, Samar et al (1995;1999) observed in this species the presence of salivary glands in the back of the tongue, in the transition region with oropharynx and palate. Thus, one may suggest that humidification of food commences from the oropharynx, which facilitates swallowing of food, which in penguins is swallowed whole.…”

Morphology of the tongue of the emu (<i>Dromaius novaehollandiae</i>). II. Histological features

“…The salivary glands in birds are generally tubular in nature with serous elements usually being absent (Ziswiler & Farner 1972), a feature also apparent in the ratites. The lingual glands of the emu were similar to those depicted in other bird species, although the structural classifi cation differed (Samar et al 1999;Bacha & Bacha 2000;Liman et al 2001;AlMansour & Jarrar 2004;Jackowiak & Godynicki 2005).…”

Changes in the Properties of Secretory Granules in the Palatine Gland Acinar Cells of the Postnatally Developing Rat

“…In the present study, we also found phospholipid in the secretory granules of the rat palatine gland acinar cells, being particularly abundant in glands at postnatal days 7 and 10. Smar et al 23) reported that Magellanic penguin palatine gland showed changes in its properties in addition to the amount of saliva it secreted during postnatal growth. Possibly in rats, phospholipid in saliva from the palatine gland might also protect the developing oral mucosa during suckling, because it was evident most conspicuously during early postnatal development and then disappeared almost entirely towards maturity.…”