Presoldier induction by a juvenile hormone analog in the nasute termite nasutitermes takasagoensis (isoptera: termitidae)

The ability of JHIII and three JHAs (hydroprene, pyriproxyfen and methoprene) to induce presoldier differentiation was tested in a highly derived termite, Nasutitermes takasagoensis (Isoptera: Nasutitermitinae), and induced presoldiers were examined morphologically and histologically. Hydroprene was the most effective hormone analog for the artificial induction of presoldier differentiation. Principal component analysis showed that hydroprene-induced presoldiers had similar external gross morphology to natural presoldiers found in the same colony. Induced presoldiers had a long, horn-like frontal projection, called a nasus, on the head. A well-developed reservoir and duct of the frontal gland were also observed inside the head. Scanning electron micrographs showed that the precursory structure forming the nasus (nasus disc) was developed under the cuticle of hydroprene-treated individuals just prior to the molt into presoldiers. Morphological changes in presoldier differentiation induced by hydroprene seemed to occur normally, compared with those in natural presoldiers. Thus, the present methods shown in this study will provide opportunities to conduct further molecular analyses on the molecular developmental bases of nasus formation during soldier differentiation in higher termites.