Amphipods are not all created equal: a reply to Bell
Duffy, J. Emmett
Hay, Mark E.
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In laboratory feeding trials, Hay et al. (1987) found that the tube-building amphipod Ampithoe longimana readily consumed the brown seaweed Dictyota dichotorna, which was not eaten by local fish. The diterpene alcohols pachydictyol A and dictyol E, which are produced by this species of Dictyota, significantly deterred feeding by fish but either stimulated or did not affect feeding by the amphipod. Based on these data, Hay et al. (1987) suggested that small, relatively sedentary mesograzers like the amphipod they studied might experience decreased predation if they lived on seaweeds that were chemically defended and thus not commonly consumed or visited by omnivorous or herbivorous fishes. Because predation is a major source of mortality for amphipods and other mesograzers (see references in Hay et al. 1987), they reasoned that selection might favor sedentary mesograzers that could live on and eat chemically defended seaweeds.