Chlorella sorokiniana KU.B2 microalga inhibits Aedes aegypti larval development

Insecticide-resistant Aedes aegypti (Linnaeus) poses a growing global challenge, reducing the effectiveness of conventional chemical control and raising the need for sustainable alternatives. Targeting the larval stage remains a key strategy in mosquito management. Here, the effects of the microalga Chlorella sorokiniana (Shihira & R.W. Krauss) strain KU.B2 on larval development, pupation, adult emergence, and mortality of Ae. aegypti were investigated, together with gut ultrastructural and histological observations. Larvae were reared under five dietary regimes: (i) rabbit food suspension alone (10 mg/mL; control); (ii-iv) rabbit food suspension maintained at 10 mg/mL supplemented with 25%, 50%, or 75% (v/v) microalgal suspension; and (v) 100% microalgal suspension. Larvae exposed to microalgae showed significantly reduced growth compared with controls. While control larvae completed development within 10 days, pupation and adult emergence were delayed and reduced in the lower microalgal proportions (25% and 50%). Conversely, larvae exposed to higher microalgal proportions (75% and 100%) remained predominantly arrested at the L2 stage (day 30), with mortality rates of 89.5% and 100%, respectively. Ultrastructural and histological analyses revealed persistence of intact and partially degraded microalgal cells in the larval gut of selected groups over time suggesting that prolonged retention of microalgal materials within the gut lumen might be associated with developmental inhibition. Fractionation experiments performed using a selected microalgal supplementation proportion (62.5%) further showed that whole microalgae, disrupted cell materials, and soluble fractions were all associated with larval developmental inhibition. Overall, C. sorokiniana KU.B2 exhibits larval development-inhibitory effects against Ae. aegypti under these laboratory conditions.