Comparison of the polychaete fauna composition from the Patagonian Shelf and the Strait of Magellan. Preliminary results from cruises shinkai maru IV, V, X, and XI (1978-1979) and second Italian oceanographic cruise (1991)

Abstract

A preliminary comparison of faunistic composition between two different areas of the Magellanic Biogeographical Province was carried out through studies on benthic poly- chaetes from the Patagonian Shelf and the Strait of Magellan. Most of the samples were taken with dredges (triangular, Charcot, Picard), from soft bottoms and sieved through 1 mm mesh screen. Twenty families represented by 36 taxa were identified in the Patagonian Shelf. The most abundant (43–65% sampling stations) families were Onuphidae, Nephtyidae and Ampharetidae, mainly with the presence of Kinbergonuphis dorsalis, Aglaophamus sp. and Ampharete kerguelensis, respectively. In the Strait of Magellan, 34 families and 119 taxa of polychaetes were identified, most of them restricted to one or two stations. Syllidae (Exogone spp., Trypanosyllis sp. and Sphaerosyllis spp.), Ampharetidae (Melinna cristata) and Maldanidae (Maldane sarsi and Axiothella minor) were the most abundant taxa. Cluster analysis indicates low similarity in species compo- sition between both sampling areas. The observed distribution pattern of austral species is considered a consequence of bottom heterogeneity, sediment composition and depth range of the collected material.