Schwenke, Theresa Magdalena (2011) Inductive chemical and mechanical defense in Fucus vesiculosus against herbivory – an analogy between East and West Atlantic populations?. (Bachelor thesis), Freie Universität zu Berlin, Berlin, Germany, 38 pp.

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Abstract

The geographic relation of inducible defenses in marine macroalgae has rarely been studied. Inducible defense in macroalgae have been reported numerous times. However, it is not known, whether different populations of Fucus vesiculosus respond differently to grazers. For this purpose I designed grazing experiments with Idotea baltica and Littorina littorea on F. vesiculosus. Algae samples were taken after 6 (7 respectively) and 11 days, and tested in dual choice feeding and no choice attachment bioassays against ungrazed F. vesiculosus samples of the same Fucus individual. I conducted these tests with F. vesiculosus from the Baltic Sea (Bülk, Germany) and the St. Lawrence River (Rimouski, Canada) to investigate inducible chemical defenses in F. vesiculosus. Furthermore I measured the toughness of differently treated Fucus thalli to localize inducible mechanical defense in F. vesiculosus. I found out that both Fucus populations induced chemical defenses against I. baltica after 6 days of grazing by I. baltica and that this effect diffused after 11 days of grazing. However inducible chemical defense of F. vesiculosus against grazing by L. littorea could not be proven in my experiments. Also I found no evidence for inducible mechanical defense in F. vesiculosus. F. vesiculosus from the St. Lawrence River were preferably consumed by I. baltica independent of the sample treatments. Considering the fact, that I. baltica does not occur in the St. Lawrence River this result was surprising.

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