Interactions of Aulacophora foveicollis (Coleoptera: Chrysomelidae) haemocytes against entomopathogenic bacteria Bacillus thuringiensis

The physiological reaction of the immunocytes of red pumpkin beetle (Aulacophora foveicollis) in response to entomopathogenic bacteria Bacillus thuringiensis (Bt) was studied at different time intervals post treatment i.e. 0, 6, 12, 24, 36, 48, 72, 96, 120 h after treatment (HAT). It showed that total haemocyte count (THC) of Bt treated insects were significantly decreased from 6 HAT and the lowest decrease in THC was observed at 120 HAT. The differential haemocyte count (DHC) after Bt treatment showed that the prohaemocyte (PR) count showed significant reduction from 24 HAT onwards. The plasmatocytes (PL) and granulocyte (GR) count was significantly increased from 6 HAT which depicts that they were the primarily involved in the immune functions. The coagulocyte (CO) count showed significant increase at 24, 36, 48, 72 and 96 HAT while the oenocytes (OE) count showed a significant increase only at 120 HAT. The haemocytes showed morphological alterations like vacuolization, cytoplasmic extensions, formation of pseudopods and degranulation on treatment with Bt. And also the defence mechanisms, such as phagocytosis, encapsulation and nodulation were exhibited by (A) foveicollis against (B) thuringiensis.