ADIPOSE TISSUE OF DROSOPHILA MELANOGASTER. I. AN EXPERIMENTAL STUDY OF LARVAL FAT BODY.

Abstract

AbstractMorphological, cytochemical and developmental studies were undertaken of the adipose cells present in third instar larvae and in adult females of Drosophila melanogaster. The adipose cells of the adult type in the abdomens of recently emerged and seven‐day‐old adult females contain deposits of lipid and glycogen. Although the cells increase in size during this period, their nuclei do not. During the third instar the larval adipose cells and their nuclei undergo a five‐ and twofold increase in average cross‐sectional area, respectively. Deposits of lipid and glycogen are present throughout this period. Proteinaceous globules first appear in the middle of the third instar. They increase in diameter and number until just before pupation they comprise one fourth of the cytoplasm of the cells. In the young adult the surviving larval adipose cells and their nuclei have decreased in average cross‐sectional area by two and three times, respectively, from the late third instar values. The surviving larval adipose cells contain droplets of unsaturated lipids, protein globules, and deposits of glycogen which completely fill the remaining cytoplasmic area. By the third day of adult life these cells histolyze. When late second instar larvae are starved for three days, the average cross‐sectional area of their fat body cells decreases ten times. Despite the absence of glycogen and a huge decrease in lipid, protein globules form, and by the third day of starvation comprise one fourth of the cytoplasm. Transplantation experiments demonstrate that a hormone produced by the ring gland during the late third instar induces the formation of these protein globules.