Dual characteristics of Bellamya aeruginosa encountering Microcystis aeruginosa: Algal control and toxin depuration

The benthic gastropods Bellamya aeruginosa (B. aeruginosa) is ubiquitous in freshwater in China and neighboring countries with great edible value. It has been recognized as a potential manipulator to control harmful algal blooms due to its filtration on algal cells. In this study, the control effect of B. aeruginosa on toxic and non-toxic Microcystis aeruginosa (M. aeruginosa), and the accumulation and depuration of microcystins (MCs) in the snail were systematically explored. Results indicated that although toxic M. aeruginosa could protect itself via producing MCs, the introduction of B. aeruginosa could still effectively inhibit the algae with cell density below 1 × 106 cells/mL. Hepatopancreas was the primary target of MCs in all tissues of B. aeruginosa, presenting a maximum of 3089.60 ng/g DW when exposed to toxic M. aeruginosa of 1.0 × 107 cells/mL. The enrichment of MCs in other tissues following the order of digestive tract > gonad > mantle > muscle. Interestingly, snail could again excrete previously enriched MCs when transferred to non-toxic M. aeruginosa, giving rise to over 80% reduction of MCs in the body. After depuration, the estimated daily intake (EDI) of free MCs in intact individuals and the edible parts of B. aeruginosa were both lower than the tolerable daily intake (TDI). These results implicated that B. aeruginosa could control low density of M. aeruginosa in spring. Particularly, the snail could be perfectly safe to consume by purifying for a while after using as manipulator.