The effects of social interaction of Reticulitermes speratus (Isoptera: Rhinotermitidae) on the conidia-mass elongation of the termite exoparasitic fungi Termitaria sp. (Deuteromycetes: Termitariales)

The termite exoparasitic fungus Termitaria sp. sometimes has a protuberant mass on the surface of the sporodochium when found in isolated conditions. To investigate how termites eliminate the fungi from their body surfaces, we focused on this protuberant mass of Termitaria sp. on the Japanese subterranean termite Reticulitermes speratus. Based on morphological observations performed with the SEM and optical microscope, this mass was shown to be composed of conidia, which were connected to each other and intricately intertwined but easily divided into individual conidium. The growth of the conidia-mass after 48 hours of infected individuals isolated from or kept with nestmates was significantly different (P<0.01; Mann-Whitney U test). These results, together with the preliminary observations of the conidia in the foregut contents of non-infected workers kept with infected individuals, suggest that social interactions, such as grooming, play an important role in the elimination of the exoparasitic fungi from termite bodies. We also suggest that measurement of conidia-mass elongation is a useful index for estimation of social interactional effects on the exoparasitic fungi.