

THE DISTRIBUTION OF PELAGIC 



POLYCHAETES IN THE SOUTH 



ATLANTIC OCEAN 



By Norman Tebble 

 British Museum (Natural History) 



(Text-figs. 1-52) 



INTRODUCTION 



The object of this report is to investigate the distribution of pelagic polychaetes in the South 

 Atlantic Ocean in relation to their environment. It is a contribution to the work on the distri- 

 bution and dispersal of plankton in the Southern Oceans formerly directed by the Discovery Com- 

 mittee and now continued by the National Institute of Oceanography. As a zoogeographical study it 

 is also intended to be an extension of C. C. A. Monro's (1930, 1936) systematic analyses of the 

 polychaete fauna of the Southern Oceans. 



The report is in two main parts: systematic account and zoogeography. It is fundamental 

 in a zoogeographical survey to define the units involved — the species — and the Systematic Account 

 forms an integral part of this paper. The principal water masses have been found to influence the 

 distribution of many pelagic polychaetes in the South Atlantic Ocean ; the zoogeographical account 

 has been separated therefore into two sections, Hydrological Environment and Distribution of Species. 

 In the former the characteristics of the water masses are described and in the latter the distribution of 

 species is considered in relation to these. Details of the number of specimens and species collected 

 at each station are tabulated in the tables and appendices. 



The treatment of some species from the South Atlantic Ocean is necessarily incomplete, because 

 the distribution of endemic antarctic species and of antarctic and sub-antarctic cosmopolitan popu- 

 lations is more properly a circumpolar study. However in the present state of our knowledge it was 

 felt that a study of the group as a whole was necessary ; it is hoped to make circumpolar distribution 

 the subject of a future report. 



It has not been possible to examine all the very numerous plankton samples collected by the 

 Discovery Investigations in the South Atlantic Ocean. The material first examined, principally from 

 South Georgia and along the Greenwich Meridian, was sorted by the staff of the N.I.O. and included 

 also the specimens reported by Monro (1930, 1936); subsequently many more hauls were examined 

 in order to extend the work over as wide an area as possible. 



The complete development of pelagic polychaetes from the fertilized egg to sexual maturity is 

 unknown, but development is probably direct without metamorphosis. Age groups are almost im- 

 possible to define in the present state of our knowledge, and the majority of the specimens described 

 in this report are therefore at indeterminate stages of development. 



