Deep-Sea Carrion Feeding Amphipods: Evolutionary Patterns in Niche Adaptation

Abstract

Extensive use of baited traps in deep-sea collecting during recent years has shown fishes and amphipods to be the dominant carrion-feeders in the abyssal habitat. All amphipods regularly obtained in such deep-sea traps belong to the family Lysianassidae. In the present investigation five carrion-feeding deep-sea lysianassids from the Atlantic and the Pacific have been studied with respect to possible adaptations for their particular ecological niche in the chemosensory equipment and the alimentary system. The special arrangement of chemosensory organs on the lysianassid antennulae can be seen as a general adaptation for chemosensory food localization, better developed than in most other amphipods. There is no immediately obvious difference in this respect between related deep-sea and shelf taxa. In the mandibles modification for dealing with large carrion has led to far-reaching morphological transformations away from the traditional amphipod pattern and apparently along different lines. In all species the alimentary canal is adapted for large scale food storing but along two completely different and mutually exclusive lines. In one genus a progressive intestinal adaptation for storage is suggested by a comparison between one shelf species and two deep-sea species. It is obvious that within the Lysianassidae two or more widely diverging evolutionary lines have led to successful adaptation to deep-sea carrion feeding.