Selective Feeding of the Duckweed Weevil on Three Common Species of Duckweed in Japan

Abstract

Duckweed is a floating aquatic plant that inhabits freshwater ecosystems and has attracted attention for its potential applications in animal feed and biofuel production. To facilitate such practical applications, an efficient and cost-effective cultivation system is required. Duckweed weevils are among the most common and widely distributed insect herbivores that feed on duckweed. In this study, we investigated the duckweed weevils (Tanysphyrus brevipennis) behaviors and feeding preferences for three common duckweed species: Spirodela polyrhiza (Sp), Landoltia punctata (Lp), and Lemna aequinoctialis (La). Fasted duckweed weevils were placed with individual duckweed species, and the Lp consumed significantly smaller areas than Sp and La because of fewer duckweed weevil feeding events and less damage per feeding bout. In the mixed-species settings, duckweed weevils showed a clear feeding preference for Sp and La over Lp; the preference in descending order was Sp, La, and Lp. We further examined the effect of anthocyanins on preference using stress-induced anthocyanin accumulation in Sp. Plants with anthocyanins had smaller areas of consumption than those without anthocyanins, suggesting that anthocyanins serve as a deterrent to duckweed weevil feeding. In conclusion, our findings regarding the feeding preferences of duckweed weevils and the defensive role of anthocyanins provide valuable insights for the dynamics of the community composition of coexisting duckweed species, contributing to more robust and efficient duckweed cultivation systems.