The Relationship between Nutrition, Hormones and Reproduction in the Blowfly Calliphora Erythrocephala (Meig.)

Abstract

1. When female blowflies are fed unlimited quantities of ‘protein’ (marmite and milk) and sugar solutions, their corpora allata (c.a.) volumes increase before and decrease during yolk formation in normal females but hypertrophy in ovariectomized flies. If fed sugar solution alone, the ovaries of the flies do not mature and the c.a. in both normal and ovariectomized females remain small. The interpretation and control of these variations in volume were investigated. 2. When ovariectomized or normal females are fed ‘protein’, their c.a. volumes increase in proportion to the quantity consumed. When ‘protein’ is removed from the diet, the c.a. decrease in size. The c.a. respond similarly in both types of fly up to the stage at which yolk is normally deposited. If a further quantity of ‘protein’ is ingested at this stage, the c.a. of normal females increase slightly in volume and then decrease during yolk deposition. But the c.a. of ovariectomized females hypertrophy before decreasing in size. 3. The decrease in c.a. volume during yolk formation may be virtually eliminated by forcing the flies to ingest excess quantities of ‘protein’ during this phase. 4. The graded response of the c.a. to ‘protein’ consumption suggests that fluctuations of c.a. volume represent variations in activity induced (proportionately) by ‘protein’ metabolites in the blood (there is no accumulation of ‘protein’ in the gut). The decrease in size during yolk formation is due to the removal of ‘protein’ metabolites by the ovaries for the purpose of yolk formation. In ovariectomized flies, these yolk precursors accumulate in the blood causing the c.a. to become hyper-active as indicated by hypertrophy. 5. The responses of the c.a. to ‘protein’ consumption do not appear to be unduly affected by denervation, cutting of the nervi oesophagi or of the cardiac-recurrent nerve. 6. There is slight evidence that the corpus cardiacum is able to store c.a. hormone.