The endocrine and nutritional control of egg maturation in the fleshfly Sarcophaga bullata

Abstract

In Sarcophaga vitellogenesis appears to be controlled by two endocrine organs, the corpus allatum and the neurosecretory cells of the pars intercerebralis. The corpus allatum exhibits cyclic volumetric changes during reproductive cycles, but the neurosecretory cells apparently do not change cyclically. Adult females allatectomized (CA −) at pupation matured eggs fully if fed liver, but only partially when fed an amino acid diet. Seventy per cent of females CA − at emergence deposited yolk whether fed liver or the amino acid diet. Yolk was not deposited after the neurosecretory cells were removed (NSC −). Reimplantation of neurosecretory cells into NSC − females stimulated vitellogenesis, whereas implanting corpora allata or other brain tissue did not. It is suggested that the neurosecretory cells produce the gonadotropic hormone in this species. Females require dietary amino acids or proteins for yolk deposition, and during egg maturation periods they ingest more ‘proteinaceous’ food than during gestational periods. The feeding patterns of CA − and NSC − females were not greatly altered compared to controls; the retarded rates or absence of egg maturation in operated females was apparently not due to altered nutrition.