Grazing rates of Elysia tomentosa on native and introduced Caulerpa taxifolia
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The marine alga Caulerpa taxifolia Vahl (C. Agardh), recognized globally as one of the most prolific non-native species introductions, has been introduced to several temperate locations from where it has since rapidly expanded. C. taxifolia is protected by a toxin (terpenoid) in its tissues that limits grazing by native herbivores. Sacoglossan molluscs of the genus Elysia are among the few organisms that graze C. taxifolia; however, little is known about their feeding ecology. In the current study, we quantified the grazing rates of Elysia tomentosa on native C. taxifolia (Moreton Bay, Queensland) and introduced C. taxifolia (Botany Bay and Lake Conjola, New South Wales). Grazing rates were similar at Moreton Bay sites and Botany Bay; however, they were significantly lower in Lake Conjola. At the maximum observed grazing rate, slugs ate their body weight in C. taxifolia (dry weight) every 18–24 h. Differences in grazing rates between locations may be explained by differences in C. taxifolia morphology rather than native or introduced origin.
KeywordsElysia tomentosa Caulerpa taxifolia Introduced species Grazing
We thank Kimberley Townsend and the staff of Moreton Bay Research Station for assistance with lab trials and Romain Mari for assistance with field collections. We acknowledge funding provided by the Moreton Bay Research Station Community Research Scholarship and the Tangalooma Research Foundation. In addition, we thank the two anonymous reviewers whose thoughtful comments greatly improved the earlier drafts of this manuscript.
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