Toxicity, histopathological and ultrastructural effects of artemisia herba alba extract in the midgut of culex quinquefasciatus larvae, diptera: culicidae.
2009
Almehmadi, R.M. | Alkhalaf, A.A.
Crude ethanoic extract from Artemisia herba alba, was tested against the 3rd instar larvae of Culex quinquefasciatus.The larvae were exposed to serial concentrations (2.75 , 2.50, 2.25, 2M, 1.50 and 1.00 mg/l).The plant extract showed marked effects on larval mortality. Sequental observations using light and electron microscopes on effects of the LC50 value were made on gastric ceaca and midgut epithelial cells.Exposure times 6, 12, 24 and 48 hours were tested. The toxic effect of the extracts have a wide range of affecting degrees in the alimentary canal. The main alterations observed in gastric caecae and midgut were partial or total cell destruction, high cytoplasmatic vacuolization, disruption of rough endoplasmic reticulum ,cell hypertrophy and the epithelium did not maintain its monolayer appearance. At longer exposure period, the midgut epithelium cells from treated larvae appeared more elongate and swollen than cells observed from control larvae. The microvilli was degenerated After 48 hours the changes were more obivous, with the apical region of the cell bulging into the gut lumen.The cells contained large cytoplasmic spaces ,cellular damage had increased,with cells ruptured at the apical surface and leakage of cytoplasmic materials into the gut lumen. Observation of tissues sections from larvae treated for different exposure times revealed a wide and clear variations in the degree of damage occured. The present study provides a quite clear evidence regarding the mode of action of the A. herba alba extract used as bioinsecticidal for controlling mosquito larvae.
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