Tropical/subtropical amphipod genera in the Atlantic Patagonian waters

CHIESA I.L.

Aveiro

Congreso; 16 th ICA International Colloquium on Amphipoda; 2015

Universidade de Aveiro

The genera Hartmanodes (Oedicerotidae) and Garosyrrhoe (Synopiidae) have been recorded from temperate and tropical waters. Hartmanodes includes three species: H. hartmanae (J.L. Barnard, 1962) and H. murrius (J.L. Barnard, 1962), both species reported from south of California, and H. nyei (Shoemaker, 1933) reported from the Gulf of California, Gulf of Mexico, Belize and Brazil. The genus Garosyrrhoe, also comprises three species: G. bigarra (J.L. Barnard, 1962) recorded from south of California, Gulf of Mexico and the Caribbean sea, G. disjuncta (J.L. Barnard, 1969) recorded from the northwestern Gulf of California, and G. luquei Ortiz & Veledo, 1988 only found in Cuba, Caribbean Sea. In January of 2005 nineteen samples were taken off Piedras Coloradas (40° 53.081? S, 65° 07.5920? W), in San Matías Gulf, Río Negro, Argentina, between 12 - 20 m depths, using a van Veen grab and a Rauschert sledge. Thirty-five amphipod species were recognized, including specimens belonging to Hartmanodes and Garosyrrhoe. These specimens represent not only the first report of both genera for Argentine waters, but also the southest records of distribution. The finding of extant genera distributed from tropical waters to northern Atlantic Patagonia has already been mentioned for other benthic invertebrates groups. The presence of this "tropical fauna" could be explained by historical causes and the actual oceanographic conditions. During the Late Miocene times -after the opening of the Drake passage- the fauna of the Southwest Atlantic Ocean contained ?paratropical? components that probably became extinct or retreated northward, when the cold Malvinas current was fully operating. Besides, at present, the waters from the northeast San Matias Gulf are the warmest of the entire Patagonian coast. On the basis of this oceanographic scenario, it is possible to speculate that part of the amphipod fauna of the northeast San Matias Gulf could include relictual tropical genera and species.