The Role of Polyphenols from the Tropical Brown Alga Sargassum furcatum on the Feeding by Amphipod Herbivores

Abstract
Several studies, mainly in temperate regions, have shown that the polyphenols of brown seaweeds (Phaeophyceae) are responsible for chemical defense against herbivores. In the present work, we tested the susceptibility of 4 species of tropical seaweeds from Búzios, Southern Brazil to herbivory by the amphipod Parhyale hawaiensis Dana, and also analysed the effect of different concentrations of polyphenols from Sargassum furcatum Kützing as a defense against this amphipod. Sargassum furcatum exhibited low levels of polyphenols, consistent with previous observations from other tropical regions, and the natural levels of phenols found in this alga did not inhibited herbivory by Parhyale hawaiensis. On the other hand, high levels of the polyphenols extracted from Sargassum furcatum and the phloroglucinol monomer of the polyphenols inhibited this amphipod. The results obtained reveal that phenolic compounds could be used as an effective defense, but for unknown reasons they are not produced in high quantities by southern Brazilian brown seaweeds, as they are in other regions of the Pacific Ocean.