Polychaetes from the Atlantic seamounts of the southern Azores: biogeographical distribution and reproductive patterns

Abstract

A study of the polychaetes living on isolated seamounts was undertaken to give data on marine biogeography and the dispersal of marine invertebrates. The data from the Meteor and Josephine seamounts came from Hartmann-Schröder and Rosenfeldt's work in the 1980s. Data from Hyeres came from Bellan's work in the 1960s, and data from the Atlantis and Hyeres seamounts were obtained during the Seamount 2 French expedition on board the ‘Suroît’ in 1993. Thirty-five sites from 280 to 2205 m were sampled: 16 on Atlantis (13 with polychaetes), and 19 on Hyeres (16 with polychaetes). In all 84 polychaete taxa from four seamounts were studied: Atlantis, 36; Hyeres, 33; Josephine, 34; and Meteor 50, but data analysis was based on the following number of taxa: Atlantis, 31; Hyeres, 29; Josephine, 34, and Meteor 48. Two groups of sites were identified by cluster analysis: I, Atlantis and Hyeres; and II, Josephine and Meteor. Only seven species were present at all sites. Nine families were present only in group I and six other families only in group II. Hesionidae (three species) occurred in group I, conversely Syllidae (16 species) were sampled only in group II. Some of the species were cosmopolitan (31%), 49% had a large distribution in the Atlantic, 11% were lusitano–mauretanian species, and only 6% were endemic; 51% of the species have direct development against 46% of the species which had a planktotrophic development and 3% a lecithotrophic development. Results of the biogeographical distribution and reproductive patterns of the polychaetes collected on these four sites were compared.