The increasing emphasis on the assessment and ecological monitoring of freshwater ecosystems has highlighted the necessity to deploy and subsequently evaluate appropriate biological indices.
In the present study, haemopoietic tissue imprints and flowcytometric analysis were employed to assess the impact of plant pesticide, azadirachtin (at No Observed Effect Limit concentration) on the cellular composition of head kidney cells from freshwater carp, Labeo rohita . The small lymphoidhemoblast decreased signi?cantly throughout the experimental tenure whereas transient stages (i.e. basophilic erythroblasts, polychromatophilic erythroblasts and acidophilic erythroblasts) increased significantly suggesting the immediate requirement of younger erythroid cells into circulation post agrocontaminant exposure. Among leucocytes, the percentage of neutrophils rose and percentage of lymphocyte decreased signi?cantly suggesting the impaired leukopoietic ef?ciency. Flowcytometric analysis clearly subdivided the entire head kidney cell population into two separate groups, viz. granulocytes and lymphocytes. In a time dependent and dose independent experiment, these two populations showed significant variation (P value .000 and .003) and Pearson correlation suggested that both are negatively correlated (-.718).
Flowcytometric measurement of ROS production showed linear regression throughout the experimental tenure. A significant rise in ROS production indicated that these are good “oxidative stress biomarkers”for the ecotoxicological assessment of any pollutants, even in a limited exposure. Thus, this study establishes a novel and easy approach towards characterization of fish head kidney cell population which can be exploited to compare patternof quantitative cell subpopulation alteration due to external stress factor and an alternative system for immunotoxicity testing of xenobiotics in native freashwater fishes.
Key words: Azadirachtin, head kidney, erythrocytes, leucocytes, flow cytometry, Reactive oxygen species (ROS), biomarker, Labeo rohita .