Effect of corpus allatum and ovaries on amount of pupal and adult fat body in the housefly, Musca domestica

Abstract

The stage of ovarian development was compared with changes in the volume of abdominal fat body in female houseflies. Pupal fat body volume decreased during each stage of oögenesis and had its maximum rate of volume decreases during the vitellogenic phase of oögenesis (stages 4 to 9). No pupal fat body remained in flies with mature (stage 10) eggs. Adult fat body showed a volume increase during egg stages 2 to 7 and 9 to 10 but decreased during egg stages 7 to 9. Both ovariectomy and allatectomy resulted in a depressed rate of pupal fat body disappearance. This was attributed to the absence of functional ovaries in the allatectomized and ovariectomized females. It was hypothesized that the developing ovaries may act as a nutritional sump for vitellogenic precursors present in the fat body and/or an ovarian hormone may stimulate cytolysis of the pupal fat body. By so doing the pupal fat body volume would decrease more rapidly when developing ovaries were present. The adult fat body volume was not affected in allatectomized or in allatectomized plus ovariectomized flies, but increased in volume in ovariectomized flies. Topical applications of synthetic juvenile hormone on mature female flies resulted in an increased adult fat body volume. From this it was concluded that ovariectomy removed the inhibition on the corpus allatum and resulted in an increase in juvenile hormone titre which caused an increase in adult fat body volume.