Termites cannot digest cellulose. But they enjoy the help of endosymbionts.
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Plants tend to resist digestion. Even the most tender vegetables have cell walls composed of cellulose—a substance that human beings cannot digest. Cows cannot digest it either, but they have help from resident microorganisms that sit around in the cow’s stomach waiting for the grass to come. When the expected nourishment arrives, they attack it with vigor, breaking down the cellulose into units that the cow can digest.
Wood is even harder to digest. Even termites cannot do it. But like cows, termites have help. Tiny one-celled animals and bacteria live in the intestines of the termite and solve the wood digestion problem. Some of these resident helpers are protozoans that belong to the genus Trichonympha. Another is a strange animal called Myxotricha paradoxa.
It seems as if the bacteria are the creatures that actually tackle the wood. They produce an enzyme called cellulase, which breaks down the long cellulose polymers into manageable units that the termite can digest.
Sometimes these symbiotic relationships assume an amazingly complex character. For example, Myxotricha paradoxa lives in a termite called Mastotermes darwiniensis. But while enjoying the hospitality of the termite, this strange creature serves as host for several species of bacteria. Myxotricha even uses one of the bacteria for swimming. Spirochaete bacteria have part of their body embedded in the cell membrane of Myxotricha while the rest or their bodies stick out like little hairs, which the protozoan uses to swim about in the termites gut. Other bacteria residing in Myxotricha tackle the cellulose, and all share in the resultant feast. Not only the bacteria, but also the protozoan and the termite partake of a delicious wood cocktail.
“Practical Zoology: Invertebrate” by Dr. S.S. Lai