Histopathological effects of chlorpyrifos on the midgut of 3rd larval instar of oriental latrine fly, Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae)
Shagufta Yasmeen, Mohammad Amir
Chrysomya megacephala, is a common blow fly species of medical importance in many parts of the world. Larvae of this species are known to cause myiasis in several mammal species, including humans. The gut of C. megacephala larva is a single, long tubular organ system, consisting of the stomodaeum, mesenteron, proctodaeum and accessory organs projecting from the main digestive tube. This study aimed to investigate the midgut of 3rd instar larvae of C. megacephala at the ultrastructural level using light microscopy. Sublethal doses of insecticide chlorpyrifos (0.02%, 0.04% and 0.2%) were provided in food to 3rd instar larvae at two different time periods (24 hours and 48 hours), to examine the alteration from normal histology of midgut. This study indicated that midgut was highly affected after 24 and 48h post-treatment and the intensity of the histopathological effects was dependent on time period and the concentration used. In midgut, treated larvae showed loosely attached epithelial layer in sections which became filled with vacuoles at higher concentrations. Epithelial cells became more or less circular in shape and highly separated from each other but on increasing the concentration, significant elongation in epithelium cells and decrease in lumen of the midgut were seen. The number of epithelial cells has been reduced. The peritrophic membrane was clustered in the centre of the lumen. Outer muscular layer and basement membrane were also affected. The results suggest that chlorpyrifoscould be used as an effective insecticide for the control of C. megacephala.