The diets of six species of the carrion-feeding lysianassid amphipod genusAnonyxand their relation with morphology and swimming behaviour

Abstract

Abstract Mandible morphology, maximum body length, and gut contents of six species of Anonyx from the Saint Lawrence Estuary were examined. All species are primarily carrion feeders, which is consistent with the morphology of the mandibles. They divide into two groups according to 1) maximum length, 2) the importance of detritus in their diets, 3) swimming behavior, and 4) the feeding condition of sexually mature individuals. The large (28—35 mm) A. nugax, A. makarovi, and A. sarsi prey to some extent on polychaetes and suprabenthic or pelagic crustaceans, while the small (12–18 mm) A. lilljeborgi, A. compactus, and A. ochoticus rely more on detritus. Overall mandible shape differs little among species, but proportionately wider incisors and taller molars occur in large species. Young stages of the siX species are prone to detritus feeding. Data suggest large species do not feed when sexually mature, while small species continue feeding. The significance of body size and swimming behavior for diets is dis...