The aerobic and anaerobic utilization of metabolic energy during insect metamorphosis.

Abstract

Summary.The investigation is carried out on the fly Calliphora erythrocephala and concerns how the metabolic energy is utilized during the metamorphosis and which metabolic pathways are followed.The amount of protein, carbohydrate and fat were determined during the pupal life by the aid of biochemical analysis and by histochemical detection. The corresponding enzyme systems and the phosphorus metabolism were also studied.No nitrogen excretion occurs during the pupal life. The decomposition of proteins occurs only to a limited extent and goes probably only as far as to peptides. These peptides seem to be combined with phospholipids.The main fuel during the pupal development is fat supplemented by a small amount of carbohydrate. Very probably there is an interconversion of fat and carbohydrate. Anaerobically only carbohydrate is utilized. Principally the same glycolytic processes work aerobically as anaerobically. The anaerobic utilization of energy is very low compared with the aerobic. Anaerobiosis represents anabiosis.The U‐shaped metabolic curve can be explained by a corresponding decomposition of oxidative enzymes. Three physiologically‐conditioned periods during the pupal life can be distinguished: histolysis, histogenesis and differentiation. During the differentiation an incorporation occurs of soluble protein into the cell structure, a fixation of enzymes in the mitochondria. The adenosine triphosphatase activity is restored first during the differentiation period.Different pathways are utilized for energy gain. Thus, the glycolytic and the cyclophorase systems show an alternating variation during the metamorphosis indicating that growth and glycolysis are connected as well as differentiation and cyclophorase system. The glycolytic and the cyclophorase systems do not seem to be strictly cocatenated.The influence of anaerobiosis on respiratory enzymes was studied. During anaerobiosis an inactivation of the protein part of the enzymes occurs. By investigation of the restitution period histolysis was found to be an active process. The lethal influence of anaerobiosis on the developmental stage of the pupa is correlated to the respiratory activity with the exception of 70 per cent of the pupal age, where a temporarily increased lethal influence was found. This marks this state as a critical period in the development.The phosphorus metabolism was closely studied. The variation in amount of different phosphorus‐fractions during the development was established. The total phosphorus is constant during the metamorphosis period. Protein‐phosphorus, a part of the lipid‐phosphorus and the more easily hydrolyzable phosphorus have a U‐shaped variation. Low molecular phosphorus compounds are liberated during histolysis and later on incorporated. Des‐oxyribonucleic and ribonucleic acid vary inversely. An increase is desoxyribonucleic acid‐content is found in the histolysis center which do not correspond to an increase in Feulgen positive substance. The utilization of adenosine triphosphate decreases during histolysis, increases during histogenesine and decreases again during differentiation in accordance with the occurrence of synthetic processes.