The role of polyphenols from the tropical brown alga Sargassum furcatum onthe feeding by amphipod herbivores

Several studies, mainly in temperate regions, have shown that the polypheno ls of brown seaweeds (Phaeophyceae) are responsible for chemical defense ag ainst herbivores. In the present work, we tested the susceptibility of 4 sp ecies of tropical seaweeds from Buzios, Southern Brazil to herbivory by the amphipod Parhyale hawaiensis Dana, and also analysed the effect of differe nt concentrations of polyphenols from Sargassum furcatum Kutzing as a defen se against this amphipod. Sargassum furcatum exhibited low levels of polyph enols, consistent with previous observations from other tropical regions, a nd the natural levels of phenols found in this alga did not inhibited herbi vory by Parhyale hawaiensis. On the other hand, high levels of the polyphen ols extracted from Sargassum furcatum and the phloroglucinol monomer of the polyphenols inhibited this amphipod. The results obtained reveal that phen olic compounds could be used as an effective defense, but for unknown reaso ns they are not produced in high quantities by southern Brazilian brown sea weeds, as they are in other regions of the Pacific Ocean.