The salivary glands of the camel: An element of adaptation to desert conditions and mitigation of climate change impacts

The one-humped camel is well-adapted to low nutritive resources, arid environments and desert ecosystems. Salivary glands have an essential role in moistening and swallowing the ingested food and forestomach digestion regulation and in water body homeostasis. The present study aims to find out the morphological, histological and histochemical characterization of the salivary glands of the dromedary camel concerning the salivation process's role in challenging the arid conditions and to mitigate the climate change impacts. Representative samples of the salivary glands of healthy 16 adult one-humped camel (Camelus dromedaries) of both sexes were tested including mandibular glands, parotid glands, sublingual glands, buccal glands, lingual glands, labial glands and palatine ones. The samples were processed according to the following handling: gross examination, fixation, dehydration, clearing, wax impregnation, embedding, trimming, sectioning, slide mounting, hematoxylin-eosin (H&E) and a battery of histological and histochemical staining. The salivary glands demonstrated variable types of tubule-acinar and tubule-alveolar secretory portions surrounded by numerous myoepithelial cells and armed with interlobular and intralobular ducts rich with goblet cells. In addition, the glands showed variable secretory cells (mucous, serous, mucoserous and mixed seromucous) with variable secretory products mainly mucusubstances, neutral mucin, acidic mucosubstances, sialomucins, sulphomucins, and29T glycoproteins. Moreover, the glands collectively demonstrated activities for the following enzymes: dehydrogenases, phosphatases, esterases, carboxylases, aminopeptidases, peroxidases, cytochrome oxidases and carbonic anhydrases. furthermore, the glands exhibited alcianophilia and metachromasia. The findings of the present study indicate that the structure and the secretion of the salivary glands of the camel support an efficient salivation process and represent a strong challenge to growing water scarcity and expansion of xerophytes as the main pastoral resources for camels. In that sense, salivary glands in camels are one of the elements of his panoply adaptation to arid conditions and to mitigate the climate change impacts.