Fat body remodeling in Spodoptera litura F. (Lepidoptera: Noctuidae) during postembryonic development

Abstract

During insect metamorphosis, larval structures including fat body are replaced by the adult ones. This process involves lysosomal enzyme-mediated remodeling of fat body. The objective of this study is to characterize the events leading to fat body remodeling during postembryonic development in an important agricultural pest, Spodoptera litura. Present study showed that the fat body undergoes significant changes in its morphology as well as histology. During the larval stage the tissue is primarily synthetic and secretory in nature and releases large amount of macromolecules including hexamerins in the heamolyph. While at pre-pupal and pupal stages it acts as a storage tissue and accumulates number of protein granules. Radiolabelling and DNA analysis studies revealed higher content of DNA in the larval fat body. The decline seen in pre-pupae corroborated well with disintegration of nuclei which were remodeled during pupal and adult stages. Further, the role of an insect morphogenetic hormone, 20-hydroxyecdysone (20E) in fat body reorganization has also been elucidated. This study enables us to understand the basic mechanism and altered micro-environment of the dynamic fat body tissue during larval-pupal-adult transition and metamorphosis.