A comparative investigation was undertaken to evaluate the diversity and community composition of freshwater molluscs inhabiting lotic and lentic environments within the Bhima River basin, India. Across both habitat types, a total of 18 molluscan species were recorded, encompassing 4 taxonomic orders and 7 families. The most frequently encountered species included Filopaludina bengalensis (Viviparidae), Tarebia lineata (Thiaridae), and Idiopoma dissimilis (Viviparidae). Species richness exhibited a marginally higher value in lotic systems relative to lentic counterparts. Noteworthy was the consistent presence of Lamellidens corrianus and Lamellidens marginalis (Unionidae) in both habitat types, reflecting their ecological plasticity. Gastropod taxa predominated over bivalves across all surveyed locations. The results further indicate that spatial variation in physico-chemical parameters exerts a significant influence on molluscan community structure. This study enhances the understanding of habitat-specific biodiversity dynamics and the environmental determinants governing mollusc distribution in freshwater ecosystems.

Physico-chemical parameters, Jawalgaon Lake, Bhima River, Freshwater molluscs, Lentic, Lotic, Solapur

This comparative analysis of the freshwater mollusc community in the Bhima River basin successfully identified the structural differences and environmental mechanisms driving population dynamics in lotic and lentic habitats. The molluscan fauna exhibits strong regional eurytopy, confirmed by the identical species richness (S = 18) shared between the lotic (Machnur) and lentic (Jawalgaon) habitats. This suggests a community adapted to the broad, regulated, and anthropogenically modified hydrological conditions characteristic of the Deccan Plateau. Significant differences in community structure were quantified: the lentic environment demonstrated higher species evenness (H = 2.560), reflecting physical stability, while the lotic environment exhibited higher total abundance (N = 5435) but lower evenness, indicating dominance by highly successful, likely pollution-tolerant, taxa. The lotic system is overwhelmingly limited by acute physical stress, evidenced by the exceptionally strong negative correlation between abundance and Turbidity (r = -0.8933). The concurrent negative correlation with Dissolved Oxygen (r = -0.5339) further suggests that the community structure has been functionally skewed toward hypoxia-tolerant species that thrive in organically polluted waters. The lentic system is predominantly limited by chronic climatic stress, indicated by the moderate negative correlation with Temperature (r = -0.5804), suggesting physiological constraints associated with thermal stratification. Nutrient dynamics reinforce this: Orthrophosphate acts as an indicator of undesirable agricultural runoff, linking community decline to watershed disturbance. The study concludes that local anthropogenic stressors, rather than fundamental flow differences, are the primary drivers shaping mollusc abundance and distribution, necessitating targeted, site-specific water quality management interventions.

Megha O. Mulajkar and Raghvendra S. Vanjari (2025). Mollusc community in Lotic and Lentic Habitats in the Bhima River Basin, India. Biological Forum, 17(10): 60-70.