Changes in esterase activity in the spinning gland cells of Diacrisia obliqua (lepidoptera) during sequential stages of development.

Abstract

Esterase activity has been studied for the first time during different phases of cellular activity i.e. growth, prefunctional, functional and post functional (degenerating) ones in the spinning gland cells of the Indian moth D. obliqua.Esterase activity is in keeping with the needs of energy of the growing spinning gland cells which is associated with increased metabolism of the cell rather than the secretion of silk. The enzyme also seems to play a significant role in the termination of larval period.The investigators have expressed conflicting ideas regarding the localization and activity of esterases in different tissue cells of insects. While some have confined their study to single instar only (2, 5), others have reported the presence of lipolytic enzymes in different cell types during growth and metamorphosis (8, 9). Present work is an attempt to study the pattern of localization and activity of esterases in only one cell type at various phases of activity in sequential developmental instars and metamorphosis. MATERIALS AND METHODSThe insects D. obliqua were collected from the castor gardens around Allahabad and reared in the laboratory at a temp. 25-27°C. Spinning glands were dissected out at different stages of development (larvae, prepupe and pupae) and sectioned 6-8 um thick, with cryostat. a-naphthyl acetate method (6) was employed to detect esterase activity in the cells. Control experiment were run side by side in which : (a) the substrate a-naphthyl acetate was omitted from the incubating mixture. (b) 0.1 M solution of arsanilic acid and 1 gm potassium fluoride were used as inhibitors. OBSERVATIONSThe enzyme esterase detected by a-naphthyl acetate method, shows positive activity and specific localization in the cytoplasm of the spinning gland cells. In the first, second and third instars the cells show moderate enzymatic activity in the basal and apical cytoplasm as well as around the nuclei (Fig. 1). 415