Effects of lignins as diet components on the physiological activities of a lower termite, Coptotermes formosanus Shiraki

Abstract

We investigated the effects of lignins as diet components on the physiological activities of a lower termite, Coptotermes formosanus Shiraki. Artificial diets composed of polysaccharides with and without purified lignins (milled-wood lignins) from Japanese cedar (softwood), Japanese beech (hardwood), and rice (grass), were fed to C. formosanus workers. The survival and body mass of the workers as well as the presence of three symbiotic protists in the hindguts of the workers were then periodically examined. The survival rates of workers fed on diets containing lignins were, regardless of the lignocellulose diet sources, significantly higher than those of workers fed on only polysaccharides. In addition, it was clearly observed that all the tested lignins have positive effects on the maintenance of two major protists in the hindguts of C. formosanus workers, i.e., Pseudotrichonympha grassii and Holomastigotoides hartmanni. Overall, our data suggest that the presence of lignin is crucial to maintaining the physiological activities of C. formosanus workers during their lignocellulose decomposition. Our data also suggested that some components, possibly minerals and/or non-structural carbohydrates, in grass lignocellulose negatively affect the survival of C. formosanus workers as well as the present rate of the symbiotic protists in their hindguts.