Are polyphenolics valuable in anti-herbivory strategies of submersed freshwater macrophytes?

Experiments were conducted to study the interspecific plant preferences of the snail Radix swinhoei on eight common submersed macrophytes species in Liangzi Lake, China, considering the various tannin content quantities of these plant species. The daily consumption rate of a tannin-rich plant species (Myriophyllum spicatum L.) was tested against each of seven other plant species in choice and non-choice tests. Five of the 7 comparisons in choice tests, and two of the 7 comparisons in non-choice tests showed that leaves of M. spicatum were un-preferred food for pulmonate snails. The other comparisons did not show significant differences. In addition, comparisons of tannin content and intake rate of senescent tissues were performed for M. spicatum and one tannin-poor species, V natans. Senescence did not change plant species preference. Dry matter content, carbon, nitrogen and ash content were measured for each plant species, but none of them can explain the observed herbivory patterns.