A reappraisal of the hormonal regulation of larval fat body histolysis in female Drosophila melanogaster.

The histolysis of larval fat body cells in adult female Drosophila melanogaster was examined in wild type and mutant animals. The fat body cells of wild type (Canton-S), apterous56f homozygotes, apterous78jts homozygotes and heterozygotes, apterous4/+, ecdysoneless1 homozygotes and heterozygotes all underwent histolysis normally during the 72 h following adult eclosion. Only in the case of ap4/ap4 adults did the cells fail to histolyze normally. The fat body cells of both diapausing and non-diapausing wild type females underwent histolysis at the same rate. Attempts to demonstrate histolysis in vitro were unsuccessful, even in the presence of juvenile hormones (JHs), larval ring glands, or adult ovaries. In all strains other than the ap4 homozygotes, a significant proportion of larval fat body cells were dead at any time while the ap4/ap4 animals, almost all cells remained viable. It is postulated that fat body cell lysis following eclosion is not a JH-mediated event, but is elicited by an as yet unidentified factor(s), possibly originating in the ovary.