MALACOFAUNAL TAXONOMIC DIVERSITY IN RELATION TO PHYSICOCHEMICAL PARAMETERS OF RAIWADA RESERVOIR, ANAKAPALLI DISTRICT, ANDHRA PRADESH, INDIA

A total of 18 molluscan species, representing two classes, three orders, and eight families, were recorded from Raiwada Reservoir during 2023–2025. Gastropoda dominated the assemblage, contributing 66.67% at the class level, 87.50% at the family level, and 72.22% at the species level, while Bivalvia accounted for 33.33%, 12.50%, and 27.78%, respectively. Among the orders, Mesogastropoda was the most diverse, comprising four families, six genera, and nine species, whereas Basommatophora and Unionida exhibited lower diversity. Seasonal assessment of physico-chemical parameters indicated higher values during pre-monsoon, followed by post-monsoon and monsoon. The Water Quality Index (WQI) reflected similar trends, with values of 49.92 (pre-monsoon), 45.55 (post-monsoon), and 35.69 (monsoon), indicating generally good water quality. One-way ANOVA revealed no significant seasonal variation in WQI (F = 0.00245; p = 0.997), suggesting stable water quality throughout the year.