Effects of Chlorella sorokiniana KU.B2 microalga on the development of Culex quinquefasciatus (Diptera: Culicidae) larvae.

Culex quinquefasciatus (Say) is a significant vector of lymphatic filariasis and arboviruses. Current control strategies rely heavily on chemical insecticides, highlighting the need for alternative and environmentally sustainable approaches. This study evaluated the effects of the microalga Chlorella sorokiniana KU.B2 on the development of Cx. quinquefasciatus larvae. Larvae were reared on microalgal-rabbit food diets: a control (100% rabbit food) and four treatments with increasing proportions of C. sorokiniana suspension (25 microalgae [Al], 50Al, 75Al, and 100Al). Additional rabbit food-only controls with matched food proportions were included to distinguish microalgal effects from reduced food availability. Larval growth, pupation, adult emergence, and mortality were assessed, and gut histology and ultrastructure were examined descriptively. Higher proportions of microalgae (75Al and 100Al) were associated with failure of pupation and adult emergence, resulting in complete larval mortality. Lower proportions (25Al and 50Al) caused delayed development and reduced survival compared with controls. Larvae provided reduced amounts of rabbit food alone were still able to complete development, indicating that the observed effects were associated with microalgal inclusion rather than reduced food availability alone. Histological and ultrastructural observations revealed numerous intact and partially degraded microalgal cells within the larval gut, while recovery of viable cells after gut passage suggested that some ingested cells remained viable after transit through the larval digestive tract. Overall, C. sorokiniana KU.B2 negatively affected the development and survival of Cx. quinquefasciatus larvae in a dose-dependent manner. Further investigation into the mechanisms underlying these effects and their ecological relevance is needed.