Symbiotic protist communities in the termite Coptotermes formosanus in Japan and a comparison of community structures between workers and soldiers

SUMMARY Termites harbor a host species-specific symbiotic community composed of excavate protist species in their digestive tracts. Although termite-protist symbiosis is well known, our knowledge concerning the variations in symbiont species compositions and variations in community structures among individuals, colonies and host castes is very limited. Here we collected 11 colonies of the termite Coptotermes formosanus in the Western Japan Archipelago and investigated the variations in the protist species compositions. We investigated the symbiont community structures in three host colonies, and for the first time, variations of the community structures were compared between worker and soldier castes. Three parabasalian species, Pseudotrichonympha grassii, Holomastigotoides hartmanni and Spirotrichonympha leidyi, were observed in all examined host individuals in the 11 colonies. One small trichomonadid species was found in hosts obtained from Iriomote Island and Okinawa Island. The mean symbiont community size in the workers was 30–50 times larger than that of the soldiers, and the host caste had a significant effect on the protist community structure. A principal component analysis revealed that the community structure was significantly more variable in the soldiers compared to the workers. Differences in food quality and community size between these termite castes probably affect the protist community structure and its variations.