Salivary pH and buffering capacity in frugivorous and insectivorous bats

Abstract

Histochemical and ultrastructural studies suggest that bats possess a diverse array of salivary chemistries that are associated with variation in dietary habits. Two fundamental chemical properties of saliva are pH and buffering capacity. This study documents variation in the pH and buffering capacity of whole saliva in 21 chiropteran species; frugivorous species from the families Phyllostomidae and Pteropodidae and insectivorous species from the families Vespertilionidae, Molossidae, and Rhinolophidae. Buffering capacity and pH were measured primarily in free-ranging individuals close to feeding and after a fasting period. Phyllostomids, pteropodids, and insectivores differ in salivary pH and buffering capacity at both sampling times. Insectivores produce saliva of significantly higher pH and buffering capacity than frugivores, suggesting the presence of fundamentally different oral physiologies between these two broadly defined dietary categories. Among frugivores, saliva of phyllostomids has significantly higher pH and buffering capacity after fasting than pteropodids, which exhibit the lowest values of salivary buffering capacity and pH known for any mammal. Patterns of diversity in salivary pH and buffering capacity appear to reflect dietary habits more closely than taxonomic relationships.