Abstract
A different species composition was found of the hyperbenthic family Eusiridae in the northernmost part of the North Atlantic Ocean and the southernmost part of the Arctic Ocean, where 88.9 % of the species were restricted to only one side of the Greenland-Iceland-Faeroe-Ridge (GIF-Ridge). The distribution limits of the eusirids are suggested to follow relatively sharp boundaries between water masses of different origin lying on and adjacent to the GIF-Ridge or within the area on each side of the ridge, combined with the geographical barrier effect of the ridge against dispersal of deep-water species. The diversity of the eusirids was much higher south (31 species) of the GIF-Ridge than north (9 species) of it. The diversity pattern of the eusirids is suggested to follow a latitudinal gradient evident in a northward decrease in the diversity from the equatorial Atlantic to the Arctic.
