Differential haemocyte counts of 5th instar nymphs and adults of Dysdercus cingulatus Fabr (Hemiptera: Pyrrhocoridae) treated with acephate, an organophosphorus insecticide
Five types of haemocytes have been identified in the haemolymph of 5th instar nymphs and adults of the red cotton bug, Dysdercus cingulatus. Changes in the Differential Haemocyte Counts (DHCs) have been assessed in relation to application of graded concentrations of Acephate. The haemogram profile was determined 6 hr, 1 day, 3 days, 5 days post-treatment as well as post-moulting i.e. in the adult males and females. Different types of haemocytes registered a dose-dependent response by either exhibiting increase or decrease in their relative proportions. The adipohaemocytes were the most sensitive cells to the insecticidal stress whereas the oenocytoids showed least damage to their cellular integrity. However, there was a consistent increase in the proportion of damage/unidentifiable blood cells in accordance with increase in concentration of acephate applied. Furthermore, the treated insects apparently responded by releasing more prohaemocytes, the so called “stem cells”, into the circulation as evident by increase in the percentage of these cells in treated blood smears compared to the parallel control.