THE SUPERGIANT AMPHIPOD ALICELLA GIGANTEA CHEVREUX FROM THE NORTH PACIFIC GYRE

ABSTRACT Recent collections from the central North Pacific provide evidence that the mysterious supergiant amphipod seen in deep-sea photographs from the North Pacific (Hessler et al., 1972) is Alicella gigantea. These specimens confirm that Alicella gigantea is the only known amphipod from the Pacific that has the same appearance and reaches the size of the supergiant amphipod reported by Hessler et al. (1972). The supergiant specimens from the Pacific differ morphologically in two ways from the Atlantic specimens, heretofore based on two individuals described in 1899. These taxonomic differences, which appear to be due to changes associated with maturation, are described and a key to Atlantic and Pacific specimens is provided. Various aspects of the natural history of A. gigantea are discussed from the results of our morphological analyses and from unpublished observations.