THE FAT BODY OF MANDUCA SEXTA: A DEVELOPMENTAL SURVEY OF THE STRUCTURE/FUNCTION RELATIONSHIP DURING THE FIFTH INSTAR

Abstract

Fat body tissue was taken from female Manduca larvae throughout the fifth instar. The samples were prepared for histological study and electron microscopy. Hemolymph samples were collected and analyzed for protein profile and concentration. The data showed that the fat body underwent a series of changes with development. These include an increase in cell size, and accumulation of lipid and glycogen during the feeding phase of the instar, and the formation of protein and urate granules during the wandering stage. Also apparent was the cyclic development of a reticular system on the cell surfaces. Maximum development of the system coincided with the period of highest protein concentration in the hemolymph, while its disappearance is coincident with a drop in hemolymph protein concentration and formation of fat body granules. Thus the fat body plays a synthetic role early in the instar and becomes a storage tissue as pupation approaches.