EFFECT OF AZADIRACHTIN ON VITELLOGENESIS OF LABIDURA-RIPARIA (INSECT DERMAPTERA)

This study investigates the effects of the insect growth regulator Aza dirachtin (AZA) on the ultrastructure of ovaries and fat body of the e arwig Labidura riparia. Ovarian development is severely reduced in AZA -injected females in a dose-dependent manner. Follicles exhibit degene rative changes, separation of follicle cells from the oocyte, and lack of pinocytotic vesicles as of yolk spheres in cortical ooplasm. Adipo cytes show fragmented rough endoplasmic reticulum (RER), numerous auto phagic vacuoles, multivesicular bodies, osmiophilic lipid droplets, an d many large glycogen areas. Gel electrophoresis reveals that vitellog enin is absent from both fat body and hemolymph, and that vitellin is not deposited in the ovary. These pathological effects are not linked to an absence of feeding. The effect of AZA on vitellogenesis is rescu able by Juvenile hormone (JH) treatment. The inhibition of vitellogene sis by AZA is discussed on the basis of its direct cytotoxic effect as well as its interference with the neuroendocrine system.