The Rhodnius testis: hormones, differentiation of the germ cells, and duration of the molting cycle

Abstract

Allatectomy of third- and fourth-stage Rhodnius larvae results in the production of precocious adults at the succeeding molt. When the allatectomy is performed on fourth-instar larvae, the testes of which contain spermatocysts of approximately 26 cells, spermatozoa are evident in the testis of the resulting precocious adult. If the allatectomy is performed on third-instar larvae, the testes of which contain spermatocysts of approximately 24 cells, the precocious adult never shows germ cell development beyond the early spermatocyte (28) stage, in spite of extensive metamorphosis of mesodermal and ectodermal structures. These results support the view that differentiation of the male germ cells in insects is inflexibly tied to a species-specific division sequence, and thus not directly manipulable by morphogenetic hormones. Evidence is also presented that the presence or absence of juvenile hormone influences the duration of the molt and hence the available time for germ cell division within each instar.