Secretion and formation of perimicrovillar membrane in the digestive system of the Sunn pest, Eurygaster integriceps (Hemiptera: Scutelleridae) in response to feeding

In this study, development of perimicrovillar membrane (PMM) from midgut cells of starved and fed Eurygaster integriceps (Hemiptera: Scutelleridae) was studied. Three different approaches, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), marker enzymes of the PMMs (alpha-glucosidase), perimicrovillar space (aminopeptidase), and microvillar membranes (beta-glucosidase) were used. Activities of these enzymes were remarkably low in the starved insects. Moreover, microscopic observations revealed that PMM is not present in the starved insect. Activities of enzymatic markers increased at 5h postfeeding, and TEM and SEM observations showed the formation of PMM as well as migration of double-membrane vesicles from center of the columnar cell to the cell apex. The highest PMM was observed at 20h postfeeding which at this time marker enzyme activity, such as a-glucosidase activity, was high, too. Thus, at 20h postfeeding, PMM system was evident and epithelial cells were completely covered by PMM system. After 20h postfeeding, presence of the fine holes in PMM started to be seen and at 40h post-feeding, observation showed degradation of PMM system. Thus, it could be concluded that PMM in E. integriceps is secreted by epithelial cell membrane when needed and its secretion and formation is regulated by feeding. This system was not present in the starved insects as its development takes place at 5h postfeeding. (C) 2011 Wiley Periodicals, Inc.