The extensive use of pesticides to control agricultural pests poses a serious threat to organisms of the aquatic environment. Chemicals entering the aquatic ecosystem through human activities, either accidentally or by design may cause adverse effects on the aquatic biota, including deleterious changes which disrupt metabolic activity at the biochemical levels. In the present study the impact of pesticide quinalphos on tissues (muscle, gills, hepatopancreas, spermatheca and ovary) of Spiralothelphusa hydrodroma was determined. Histological alterations and biochemical changes such as succinate dehydrogenase (SDH), lactate dehydrogenase (LDH), acid phosphatase (ACP) and alkaline phosphatase (ALP), activities in tissues had been carried out. Overall work concluded that histological biomarkers provide reliable data to discriminate the usage of pesticides which had direct influence on loss of aquatic animals.