Environmental Modulation in Larval Development of the mosquito, Culex quinquefasciatus Say: Effects of Temperature and Organic Pollution

Abstract

Introduction: Culex quinquefasciatus is the principal vector of lymphatic filariasis and an important vector of Japanese encephalitis in urban India. Aim:This study investigated the individual and combined effects of ambient temperature and organic pollution on the larval development, survival, and adult emergence of C. quinquefasciatus in Agra, Uttar Pradesh. Materials and Methods: Larvae of were collected every monthduring January, 2025 to December, 2025 from four representative breeding site categories and reared under controlled laboratory temperatures (20°C, 25°C, 30°C, and 35°C). Results: Water quality analysis revealed significant seasonal variation in biological oxygen demand (BOD), dissolved oxygen (DO), and nutrient loads. Developmental time was shortest at 30°C (7.2 ± 0.6 days) and longest at 20°C (18.4 ± 1.1 days), whereas survival peaked at 25°C (89%). Organic pollution, measured by BOD and ammonium concentration, showed a significant positive correlation with larval density (r = 0.84, P < 0.01) but an inverse relationship with dissolved oxygen. Sites with BOD > 10 mg/L supported 2.8-fold higher larval densities than clean water habitats. Conclusion: These findings demonstrate that the interaction between thermal regime and organic enrichment strongly modulates vector productivity in Agra, underscoring the need for sanitation-integrated vector management.