Feeding deterrence of Azolla in relation to deoxyanthocyanin and fatty acid composition

Abstract

Higher levels of deoxyanthocyanins in Azolla fronds correlated with feeding deterrence against adult Lymnea swinhoei snails and Polypedates leucomystax tadpoles. After 7 days in co-culture, the growth yield of Azolla filiculoides was almost twice that of Azolla pinnata, which contained approximately 20-fold higher levels of deoxyanthocyanins. Inclusion of snails upon initiating a plant co-culture resulted in an A. pinnata growth yield that was 1.5-fold higher than that of A. filiculoides. The two plant species did not differ significantly in fatty acid composition. However, snails incubated for 1 week solely with A. pinnata showed a characteristic starvation-like fatty acid profile, with a two-fold lower proportion of polyunsaturated fatty acids (PUFAs) compared to snails that had access to A. filiculoides, either as a sole food source or in co-culture with A. pinnata. A 3-month cultivation of A. pinnata with tadpoles resulted in fronds having a 260% higher concentration of deoxyanthocyanins and a 10-fold lower proportion of PUFAs in comparison to plants unexposed to tadpoles, indicating that prolonged feeding reduces the desirability of the surviving plants as a food source.