Studies on the Metabolism of Locust Fat Body

The successive accumulation and depletion of reserves in the fat body of insects shows that it is an important storage organ, but it seems possible that it is also an organ of intermediary metabolism, degrading some substances and elaborating others for use by other tissues. A study was made in vitro of the incorporation of certain metabolites, glycine, leucine, acetate and glucose, labelled with carbon-14, into the fat body of the desert locust, Schistocerca gregaria Forskal. This showed something of the degradation and synthesis occurring in locust fat body and also suggested that the tricarboxylic acid cycle functioned normally, contrary to an earlier report (Hearfield & Kilby, 1958). The results obtained from these studies on the incorporation of labelled metabolites and on the respiration of locust fat body are presented here. The fat body of S. gregaria becomes packed with fat droplets, the predominant reserve. In addition it contains abundant glycogen and protein, and ribonucleic acid can be readily demonstrated in the cytoplasm; the tissue is free from symbiotic organisms (Coupland, 1957). Schistocerca fat body has been shown to contain a number of enzymes including transaminases and the glutamic dehydrogenase system (Kilby & Neville, 1957) and an enzyme system which synthesizes trehalose from glucose (Candy & Kilby, 1959).