Developmental and metabolic changes induced by anoxia in diapausing and non-diapausing flesh fly pupae

Abstract

Anaerobic metabolism was compared in nondiapausing (ND) and diapausing (D) pupae of the flesh fly,Sarcophage crassipalpis using in vivo13C NMR spectroscopy. Anoxia-induced changes in the development of ND and D pupae were correlated with oxidative metabolism and mitochondrial integrity. ND pupae tolerated 1 day of anoxia without any obvious developmental effect, while D pupae tolerated up to 6 days of anoxia. Longer exposure to anoxia (3 days in ND pupae and up to 14 days in D pupae) allowed development to the pharate adult stage but precluded eclosion. Four-day anoxia applied to ND pupae during 4–6 days post-pupariation arrested development in a stage indistinguishable from diapause. This morphological stasis was accompanied by 80% suppression of oxidative metabolism and a 100% increase in glycerol concentration. However, unlike a true diapause, this arrest could not be terminated with 20-hydroxyecdysone or hexane. Four-day anoxia treatment applied to D pupae stimulated development and raised their oxygen consumption. The anoxia-induced changes in oxidative metabolism were not accompanied by mitochondrial changes. Exposure to 95%PO2 atmosphere had no apparent developmental or metabolic effects on ND or D pupae. Major metabolites (lipids, trehalose, glycogen, glycerol, glutamine, and alanine) were detected in the ND and D pupae but their rates of turnover differed. Anoxia induced synthesis of glycerol and alanine in both D and ND pupae. Injected labeled glucose was incorporated primarily into trehalose and glycogen by both D and ND pupae. The rate of incorporation in ND pupae was approximately twice that observed in D pupae. Anoxia resulted in glycerol and alanine synthesis in both groups of pupae, but more glycerol was labeled in ND pupae and more alanine in D pupae. Glycogen and trehalose were depleted in the D pupae under anoxia. Cold acclimation had no effect on the steady-state or rate of synthesis of metabolites.