Fine structure of the A cells of the pars intercerebralis of normal and gamma-irradiated female milkweed bug, Oncopeltus fasciatus (Heteroptera: Lygaeidae).

Abstract

AbstractNeurosecretory A cells in the pars intercerebralis of O. fasciatus were identified at the ultrastructural level. Fine structural study of the A cells of female insects during the period of production of the first batch of eggs revealed that these cells undergo qualitative and quantitative changes during the first eight days of adult life. The A cells appear to be inactive in the newly emerged females. There is a significant depletion of neurosecretory granules (NSG) in the perikarya in the 2‐day‐old females followed by an increase and decrease in the 4‐ and 6‐day‐old females, respectively. The A cells in the 8‐day‐old females showed an accumulation of NSG. The mitochondrial population increases after adult emergence reaching a peak in the 4‐day‐old females, and then declines gradually in the subsequent age groups. The effect of sublethal dose of gamma radiation on the ultrastructure of the A cells was also investigated. Radiation damage is evident as early as four hours after irradiation with 10 kR. There is considerable swelling of the lysosomes and the membrane system in the A cells of irradiated insects. Synthetic activity of the A cells, based on the distribution of the endoplasmic reticulum, Golgi complex and mitochondria, as well as release of the NSG are apparently inhibited after irradiation. Radiation‐induced damage becomes more conspicuous as post‐irradiation interval increases. It is surmised that the damage to the A cells might have contributed at least in part, to the failure of yolk deposition in the irradiated insects.