Is there differences in components of saliva among species?

Question

Are there differences in the components of saliva among species? Also, do the functions of saliva differ between species?

Answer 1

There are several differences in the components of saliva between species because saliva serves slightly different purposes from one species to another. Fundamentally, saliva serves to begin the process of digestion, elicit "taste," lubricate food to allow for easier digestion, and provide antimicrobial agents to prevent infections. In humans, these are the only functions that saliva serves. In other animals, saliva is also necessary for creating/maintaining their habitat(s), killing prey, promoting healing, etc. There is a protein in human saliva called epidermal growth factor (EGF), which inhibits gastric acid secretion, promotes DNA synthesis, prevents and heals damage of the digestive system (such as from bile), etc. Conversely, there is a protein in mouse saliva called nerve growth factor (NGF) which has been shown to increase the rate of healing two-fold when compared to wounds that hadn't been licked. These proteins serve relatively the same function - healing of tissues - but EGF in humans doesn't heal wounds outside the body like the NGF in the saliva of mice. Comparing humans to reptiles, we see that evolution provided snakes, lizards, etc. with the ability to synthesize neurotoxins, hemotoxins, and cytotoxins within their salivary glands. These toxins break down nerves, blood, and cells, respectively. The function of those components of venom are comparable to the amylase and other enzymes in our saliva that break down starches for digestion.