Distribution and activity of esterases in the enteric epithelial cells of certain lepidopteran pests during metamorphosis.

Esterases have been investigated in the enteric epithelial cells of the larva, pupae of varying ages and adult of four Lepidopteran moths--Achoe janata, Atteva fabricella, Hypsa alciforon and Paralellia algira. The foregut epithelium of the larvae, pupas and adults showed negative results for esterases. Positive sites of esterases activity were found in the peripheral region of epithelial cell of the larval midgut: the apical region being free of enzymatic activity. Escape of the enzyme from the cells into the lumen of the midgut was not observed in any of the moths presently investigated. Anterior proctodaeal epithelial cells show appreciable enzymatic activity, while those of posterior hindgut exhibit negative reaction. In prepupal stage the regenerative cells of the midgut epithelium do not show activity of the enzyme at both the apical and peripheral ends. Esterases appear in the regenerative cells after the 2. day of pupal period and thereafter positive results throughout the period of metamorphosis. Activity of the enzyme increases in the midgut digestive cells of newly emerged adult. However in the cells of hindgut epithelium there is no change in the esterases activity or localisation during metamorphosis. The following conclusions have been drawn: 1. Hydrolases investigated are esterases (not lipases) which are present in the enteric epithelium of moths. 2. With the change in the metabolic rate during metamorphosis of insects esterase activity is reduced in epithelial cells at the onset of pupal period, while in pharate as well as newly-emerged adult the enzyme activity increases.