Species richness and distribution patterns of echinoderms in the southwestern Atlantic Ocean (34-56°S)

Valeria Souto,Mariana Escolar,Claudia Bremec,Gabriel Genzano

doi:10.3989/scimar.03882.26b

Abstract

The aim of this study was to compile and analyse available historical information on echinoderms in the southwestern Atlantic Ocean in order to make a synthesis of present taxonomical knowledge, to identify patterns of geographical distribution of echinoderm assemblages and to test the validity of the current zoogeographic scheme for this group. This study was conducted on the Argentinean continental shelf, southwestern Atlantic Ocean (34-56°S). An intensive research on geo-referenced data was carried out to make a knowledge synthesis on echinoderm species and thus create a historical database. Multivariate analysis was used to analyse the faunal composition through latitudinal and bathymetric gradients as well as echinoderm associations. The results confirmed the existence of two faunal associations that correspond to the traditional zoogeographic scheme established for the Argentine Sea: the Argentinean and Magellan Provinces. The Argentinean Province had 46 widely distributed species. Of the 86 species recorded in the Magellan Province, a high percentage (25%) were also found in Antarctic waters, suggesting a strong connection between the echinoderm fauna of this province and the Antarctic Region. The species richness between 34 and 56°S in the Atlantic Ocean showed a significant increase in reference to latitude, with the highest values being recorded between 46 and 56°S. In view of the high percentage of shared species with Antarctica, considered a hot-spot region in terms of echinoderm diversity, the pattern of distribution of species richness observed in our study area could correspond to a dispersion of this species from Antarctic to sub-Antarctic regions.

Highlights

Echinoderms are benthic marine invertebrates widely distributed throughout the world ocean
The aim of this study was to compile and analyse available historical information on echinoderms in the southwestern Atlantic, in order to make a synthesis of present taxonomical knowledge and to identify patterns of geographical distribution
A total of 110 species of echinoderms distributed in 5 classes, 16 orders and 37 families were recorded in the study area (Appendix 1) according to the information available in 36 taxonomic and other published works up to 2005 (Appendix 2)

Summary

Introduction

Echinoderms are benthic marine invertebrates widely distributed throughout the world ocean. In southern South America, this group was early studied by L. Feuillée at the beginning of 1770 (Larraín 1995); during the following centuries, most information from the Atlantic Ocean was produced on the basis of material collected by HMS Challenger (1873-1876) and RV Discovery (1925-1936) (Mortensen 1936, Fisher 1940). The early work on taxonomy and biology of echinoderms of the Argentine Sea are contributions about echinoids, asteroids and ophiuroids of southern South America (Bernasconi 1947, 1964a,b,c, Bernasconi and D’Agostino 1977). Other contributions have shown the distribution patterns of the most conspicuous species in large Atlantic shelf areas, between 26 and 38°S (Tommasi et al 1988a,b), and along the shelf break frontal area, between 36 and 43°S (Escolar 2010)

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