Sunn pest, Eurygaster integriceps Putton (Hemiptera: Scutelleridae), digestive α-amylase, α-glucosidase and β-glucosidase

Morphology, pH and carbohydrate hydrolyzing enzyme activities of the Sunn pest gut were investigated in this study. The Sunn pest midgut is separated into the first ventriculus (V1), the second ventriculus (V2), the third ventriculus (V3) and the fourth ventriculus (V4). The first three regions of the midgut were acidic (pH 5.0–5.2), while the fourth region of the midgut and rectum was moderately acidic (pH 6.2–6.4 and pH 6.5–6.8, respectively). Activity of α-amylase was highest at pH 6 to 7, which correlates with the pH of the midgut. The optimum pH for α-glucosidase and β-glucosidase is 4 to 6 and 5 to 6, respectively. Different gut regions had different carbohydrate hydrolyzing enzyme activities. Carbohydrate hydrolyzing enzyme activities in V2 and V4 were the same, but activities in V1 were slightly higher than in V2 and V4 and lower than in V3. Levels of α- and β-glucosidase activities were similar in various midgut sections. However, the V3 had the highest activity followed by V4, V2, V1, respectively.