What is meant by "mutualist exploration of cellulose digestion", a phenomenon that occurs in some mammals and insects?
Herbivorous animals eat great amounts of cellulose, a substance not digest by their digestive enzymes. In these animals regions of the digestive tube are colonized by microorganisms that digest cellulose. This mutualist ecological interaction among animals and microorganisms happens, e.g., in horses, cows, rabbits and in some insects like termites.