EFFECT OF DIET ON VITELLOGENIN, VITELLIN AND ECDYSTEROID LEVELS DURING THE 2ND CYCLE OF OOGENESIS IN THE HOUSEFLY, MUSCA-DOMESTICA

Both ecdysteroid and vitellogenin exhibited peak levels of approx. 35 pg/mul and approx. 30 mug/mul, respectively, 12-24 h after oviposition when females were provided a complete diet during the first and second gonotrophic cycle. However, ecdysteroid and vitellogenin levels did not exceed 15 pg/mul and 12 mug/mul, respectively, in flies that were fed sucrose after oviposition. Nutritionally deprived flies that were fed the complete diet for 4 h after oviposition had a maximum ecdysteroid concentration of 18 pg/mul and vitellogenin levels of 14 mug/mul. Furthermore, these nutritionally deprived flies had lower haemolymph non-specific protein levels, and retarded ovarian development when compared with those given free access to the complete diet. This suggests that feeding on a nutritionally adequate diet provided materials that were required for steroidogenesis and vitellogenesis. Oviposition released a specific behaviour that caused houseflies to select the complete diet over sucrose. This selection and subsequent feeding coordinated endocrine events and provided the nutritional requirements that were necessary for the development of the second cycle of eggs.