Effect on mandibular length of juvenile hormones and regulation of soldier differentiation in the termite Reticulitermes speratus (Isoptera: Rhinotermitidae)

To understand the relationship between juvenile hormone (JH) titers and morphogenetic changes associated with soldier differentiation of the termite Reticulitermes speratus, mandibular length (length between apex and first teeth) of presoldiers induced by various concentrations of JH III (0-320 μg per dish) was measured. Presoldiers were observed when treated with more than 20 μg JH III. Both left and right mandibular lengths were significantly different among differentiated presoldiers treated with different concentrations of JH III. Concentration-dependent effects on mandibular lengths were observed: higher JH III concentrations (160 and 320 μg) caused differentiation in presoldiers with longer mandibles, and lower concentrations (40 and 80 μg) caused differentiation in presoldiers with shorter mandibles. These results suggest that morphogenetic changes specific to soldiers are influenced by JH titers (endogenous JH+applied JH III) in workers. Live soldiers could inhibit presoldier differentiation in R. speratus workers. Interestingly, mandibular lengths of presoldiers induced by JH III were influenced by soldier presence, which could influence morphological changes, probably by regulation of JH titers in workers, as recently shown in the termite Coptotermes formosanus.