Surgical inhibition of ovulation and gestation in the tsetse flyGlossina austeniNewst. (Dipt., Glossinidae)

Abstract

To determine whether the brain medial neurosecretory cells (MNC) provide a hormone regulating ovulation and larviposition in females of Glossina austeni Newst., the effects of MNC ablations, sham operations, MNC implantations, and MNC extract injections were investigated. Ablation almost always inhibited ovulation and interfered with larval development and larviposition; it did not appreciably influence blood feeding, digestion or egg maturation. However, surgical brain trauma and even general stress also inhibited ovulation in control flies to some extent, though inhibition was more frequent and prolonged after greater trauma or incisions closer to MNC. A similar relationship existed between proximity of incisions to MNC and success of larval development and larviposition. MNC implants and extracts failed to induce ovulation in ablated flies. Most evidence indicates that MNC ablation affects ovulation and larviposition, not by removing a source of stimulatory hormone, but by interfering with nervous pathways necessary either for hormone release at some other site or for direct stimulation of the reproductive tract musculature.