Effect of Chitosan on Diversity and Number of Protists in Subterranean Termites

摘要

Although protist species composition in the hindgut of subterranean termites is known to vary among termite species, less is known about the effects of biocides on protist population dynamics within a single species. The goal of this study was to observe the potential effect of chitosan, an environmentally friendly antimicrobial compound, on protist communities harbored in hindguts of Reticulitermes virginicus. Workers of two termite colonies collected from different locations were exposed to treatedwood with different concentrations of chitosan (0.5%, 1% and 2%) and two sets of control-treated (water and acetic acid-impregnated) wood specimens over a 14-day period. Protists were dissected from termite hindgut and loaded on a hemocytometer slide tocount protist species under a light microscope at 400x magnification. Ten protist species were found in colonies exposed to the control and wood treated with 0.5% chitosan. The coexistence of Trichonympha agilis and T. burlesquei in R. virginicus is reported here for the first time. Only two protist species, Monocercomonas sp. and Trichomitus trypanoides, survived in colonies exposed to wood treated with higher chitosan concentrations (1% and 2%). The total raw protist counts in these higher chitosantreatments, however, were on average 12 x less than in the controls and 0.5% chitosan. The results of this study indicate that chitosan may affect termites by acting on the protist symbionts. The species-specific response of protists to higher concentrations of chitosan can further advance the understanding of chitosan’s mode of action.