A study on some physiological characteristics of the alimentary canal of Hippodamia variegata (Goeze) (Col.: Coccinellidae)
2010
Shirafkan, Kh. | Hosseininaveh, V. | Aldaghi, M. | Allahyari, H. | Razavi Tabatabaei, P.
The coccinellid Hippodamia variegata is one of the most important predators in the biological control programs of pests specially aphids, in the stage of adults and forth instar larva. Insects were reared in a growth chamber under 23ᴼC, 70% RH and 16:8 (L:D) photoperiod. Adults and forth instar larvae were dissected and their alimentary tracts were removed. For determining of pH, eight indicator dyes were used. Homogenates from the midgut tissues were centrifuged and the resulted supernatants were used for enzymatic experiments. Hemogolobin was used as the substrate for determining of total proteolytic activity at pH range of 2 to 9. Results showed that optimal proteolytic activity occurred at pHs 3 and 4 in larvae and adults respectively suggesting the presence of cysteine and aspartic proteinases as dominant proteases in the insect which is consistent with the prevailing pH of the midgut. Preliminary zymogram analysis revealed that at least the presence of 3 proteolytic bands and the inhibitor E-64 almost disappeared 2 out of 3 proteolytic bands. Carbohydrase assays at pH 6 showed á- and â-glucosidase activity in the midgut of the larvae and adult of H. variegata.
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