Mutual Bonds
Introduction
A wounded termite with its gut spilled out was recently found embedded in a 100 million year old piece of amber. The presence of a range of protozoa in the alimentary canal of this termite is the oldest example of "mutualism". The study published in a recent issue of the journal Parasites and Vectors said that the protozoa helped the termite digest the cellulose in wood which is a big part of its diet. They secreted the enzymes aiding in digestion and in turn got shelter within the termite's body.
Source
Down To Earth, June 2009