Untersuchungen über die Bedeutung der Corpora allata für die Differenzierung der Kasten bei der Termite Kalotermes flavicollis F.

Abstract

The role of the corpora allata in caste differentiation has been studied in the termite Kalotermes flavicollis by transplanting corpora allata of differnt donors into pseudergates in normal and in orphaned colonies. When corpora allata from primary and secondary reproductives, from nymphs just before the alate moult, and from soldiers were implanted, a great number of the hosts differentiated into pre-soldiers. Transplants from pseudergates and last-stage nymphs which were not preparing for a moult, had no such effect, but those of pseudergates seemed to stimulate the production of supplementary reproductives. The absence of the reproductives or of their pheromones had an accelerating effect upon pre-soldier differentiation. In some cases intercasts between pre-soldiers and supplementary reproductives were produced. Their occurrence can be explained by an induction of a supplementary reproductive moult at a time when pre-soldier differentiation was already in progress. Intercastes between pre-soldiers and pseudergates have been produced experimentally by injecting ecdyson 10 days after the implantation of corpora allata from reproductives. Thus in soldier differentiation the moult is induced normally only some time after the onset of differentiation. Ligation experiments showed that the remarkable volume increase of the corpora allata before a supplementary reproductive moult has nothing to do with differentiation, but occurs in connexion with the production of gonadotropic hormone which in females stimulates growth of the oocytes. All transplanted corpora allata with the exception of those of last-stage nymphs, had an inhibiting effect upon the pigmentation of eyes in supplementary reproductives. This typically juvenile effect was especially significant after transplanting corpora allata from pseudergates. The corpora allata seem to produce two different hormones, which have different effects in caste differentiation. The juvenile hormone probably increases the competence for supplementary reproductive differentiation. The gonadotropic hormone on the other hand initiates pre-soldier differentiation.