Ultrastructural Changes in Midgut Cells of Helicoverpa armigera Due to Bacillus thuringiensis var. kurstaki and an Isolate BTS 42

After treatment with Btk and BTS 42 histopathological studies revealed aberrations in the four cell organelles i.e. nucleus, endoplasmic reticulum (ER), mitochondria and microvilli of midgut epithelial columnar cells. Due to crystal toxin treatments, nuclear envelope became discontinuous at several places. There was loss of double membrane structure. Nuclear pores disappeared. Nucleoplasm showed some electron lucent areas. Changes such as karyolysis of chromatin material, aggregation of chromatin material in nucleoplasm, condensation of chromatin material were observed along or adjacent to the inner membrane of the nucleus. Due to Btk and BTS 42 treatments the nucleoli disappeared or disintegrated. Changes like vesiculation, dilation and vacuolisation occurred in endoplasmic reticulum. Crystal toxins created a cribiform appearance of cytoplasm (having numerous holes). There were numerous small discrete vesicles or large vacuoles, looking like pools or lakes in place of endoplasmic reticulum. In mitochondria, cristae lost their lamellar character. They were dissolved, disintegrated and disoriented. Mitochondria were swollen. Endoplasmic Reticulum: vesiculation and swollen mitochondria constituted the change called cloudy swelling. Microvilli were distintegrated, disoriented and swollen from many places. The microvilli were detached from the cell wall and cell wall formed protruded blebs into the gut lumen.