A BIOCHEMICAL AND STRUCTURAL STUDY ON THE EFFECTS OF METHOPRENE ON FAT-BODY DEVELOPMENT IN LOCUSTA-MIGRATORIA L

An investigation was made of the development changes in fat body of Locusta migratoria (L) during the last larval instar and early adult life, and how this was disrupted by treatment with the juvenile hormone analogue methoprene. Fifth-instar larvae (12 +/- 12 h) were topically treated with 475-mu-g of methoprene and fat bodies were subsequently removed for histological and ultrastructural study at regular intervals until the 8th day of adult life. In the first half of the larval stadium, fat body cells showed increases in nuclear size and increased levels of RNA and rough endoplasmic reticulum. These changes were exaggerated and prolonged by methoprene treatment, especially in female insects. In the latter half of the instar, fat body stored increasing amounts of lipid and glycogen. Structural studies indicated that methoprene reduced the levels of stored material but extraction and quantification of fat body lipid and glycogen showed there was no significant difference from controls. Analysis of haemolymph samples showed that methoprene treatment caused the precocious appearance of a female-specific protein band in the blood. Treatment also caused the formation of mitotic bodies in fat body cells, reduced levels of heterochromatin and possibly disrupted autophagic processes.