Dietary analysis of the marine Amphipoda (Crustacea: Peracarida) from the Iberian Peninsula

The gut contents of 2982 specimens of 33 amphipod families, 71 genera and 149 species were examined, representing a high percentage of amphipod diversity in the Iberian Peninsula. Material was collected mainly from sediments, algae and hydroids along the whole coast of the Iberian Peninsula from 1989 to 2011. Although detritus was the dominant food item in the majority of amphipods, gammarideans also included carnivorous (mainly feeding on crustaceans) and herbivorous species (feeding on macroalgal tissues). Our study revealed that general assignment of a type of diet for a whole family is not always adequate. Some families showed a consistent pattern in most of the studied species (Corophiidae, Pontoporeiidae = detritivorous; Oedicerotidae, Phoxocephalidae, Stenothoidae = carnivorous; Ampithoidae = primarily herbivorous on macroalgae), but others included species with totally different feeding strategies. In general terms, detritivorous families were characterized by a stronger mandibular molar, while in carnivorous taxa this feature was less developed or reduced. The percentage of macroalgae in the digestive contents was associated in most cases with a reduction or loss of the mandibular palp. It seems that high trophic diversity in amphipods is a generalized trait along different ecosystems in all latitudes, and could be related to the ecological success of this group in marine benthic communities.