Abstract
The ultrastructure of neurosecretory cells in the pars intercerebralis were investigated in female and male pupae of the silkworm, Bombyx mori. The neurosecretory cells were classified into three types : type I, II and III, as in larvae. Only in type I cells of male pupae showed ultrastructure of the cytoplasmic change drastically from that observed in larvae.Type I cells in females were quite similar to those in larvae. Some type I cells in males 3 and 6 days after pupation showed degenerated structures, as if their neurosecretory functions were ceased. Cytoplasmic matrix decreased remarkably and neurosecretory granules decreased in their number, size and electron density. The cisternae of rER were considerably enlarged. In addition, the glial cell perikarya and glial processes which surround type I cells degraded or disappeared, resulting in the exposure of type I cells to the hemocoel.Cells of type II and type III of both sexes, however, showed no alteration in structure. Onth other hand, type I cells in females exhibited characteristics of active neurosecreting cells in both 3 and 6 day pupae and showed no degenerated structural alterations. The probability that type I cells of female pupae are involved in the production of the gonadotropic hormone is discussed in detail.
