BACKGROUND We analyse the distribution of Gastropods and Chitons from shallow to deep waters along the southwestern Atlantic Ocean off Argentina and discuss possible factors determining the observed biogeographic patterns. RESULTS Three major biogeographic groups are defined on the basis of Gastropod and Chiton species associations, i.e., continental shelf (< 350 m), upper continental slope (> 350-2000 m) and lower continental slope (2000-3000 m). Bathymetry appears as the main factor modifying large-scale distribution of the fauna at a. In this scenario, species associations are determined by marine currents that clearly occur at a particular and well defined depth. No arrangement of species by geographic location was found in assemblages from the continental shelf and upper continental slope. CONCLUSIONS We hypothesize that depth and marine currents are the main factor affecting the distribution of Gastropods and Chitons along the SW Atlantic between 200 and 3000 m depth.

中文翻译：

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沿西南大西洋的某些底栖软体动物的集合：从潮下到深海。

背景我们分析了腹足类动物和Chitons从阿根廷西南大西洋沿浅水到深水的分布，并讨论了确定观察到的生物地理格局的可能因素。结果根据腹足纲和奇顿物种的联系，确定了三个主要的生物地理群，即大陆架（<350 m），上大陆坡（> 350-2000 m）和下大陆坡（2000-3000 m）。测深法似乎是改变某处动物群大规模分布的主要因素。在这种情况下，物种关联由明显在特定且定义明确的深度的洋流确定。在大陆架和大陆上坡的组合中没有发现按地理位置排列的物种。