Feeding preferences of supralittoral isopods and amphipods

We examined the feeding preferences of 3 supralittoral crustacean species i n the Pacific Northwest of North America. The isopod Ligia pallasii (Brandt , 1833), the rocky-shore amphipod Traskorchestia traskiana (Stimpson, 1857) , and the sandy-beach amphipod Megalorchestia californiana (Brandt, 1851) h ad similar feeding preferences, suggesting that feeding preferences were ba sed on general algal traits rather than on adaptations particular to specif ic herbivores. No single trait clearly distinguished low- and high-preferen ce seaweeds, although pH and phenolic compounds may have been important for two chemically defended seaweeds (Desmarestia sp. and Fucus sp., respectiv ely). Feeding preferences of L. pallasii were affected by dietary history, but effects were minor compared with differences among seaweeds. All 3 cons umers tended to prefer wrack (aged, stranded seaweeds) over fresh seaweeds of the same species. Our results suggested that increased organic and miner al contents of wrack were important in mediating these preferences, but tha t toughness and salt and nitrogen contents were not. Reduced levels of defe nsive compounds may have made wrack more palatable than fresh seaweeds in t he case of the two chemically defended seaweeds.