Histochemical and ultramorphological visualization for storage molecules in trophocytes at postembryonic developmental stages of Bombyx mori (Lepidoptera: Bombycidae)

Abstract

The fat body originates from mesoderm during embryogenesis and it exists through the developmental stages in insects. It is equivalent to vertebrate adipose tissue and liver because it has multiple metabolic and storage functions. The fat body controls the synthesis, storage and metabolism of glycogen, lipid and protein, and it plays a major role in immune and endocrine systems and detoxification processes. Main cells of fat body, which accomplish these vital functions are trophocytes. In this study, we aimed to determine the reserve molecules like glycogen, lipid, protein and uric acid accumulated in the fat body at postembryonic developmental stages of Bombyx mori. For this purpose, we used specific histochemical techniques to determine glycogen, lipid, protein and uric acid molecules. We determined that glycogen contents are stored from the 3rd larval stage while proteins and uric acids are stored from the 4th larval stage. We also detected that the amount of glycogen, lipid, protein and uric acid increase gradually throughout the larval stage and then these molecules decrease gradually as they are used in the pupal stage. Fat body biology may require further investigations on the underlying function of the fat body formation throughout the developmental stages. It can also be used as a model in research of metabolic disorders and immune diseases.