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In polar areas, where benthic sampling is constrained by a series of limitations imposed by climate and logistic challenges, knowledge about the key elements required to plan a successful survey is fundamental. During the International Polar Year (IPY, 2007/2008), under the Census of Antarctic Marine Life (CAML), new sampling campaigns were undertaken in several Antarctic areas comprising the Ross Sea. In this region, the 2008 NIWA IPY-CAML voyage obtained benthos samples from shelf to abyssal depths. In the present study, we focus on the Mollusca from this expedition and on the possible variations in their richness and composition with latitude and depth. Given the use of sampling gears selective for different size fractions of the macrofauna, we also assess which size fraction contained the highest biodiversity. Differences were detected in species composition with latitude (averaged across depth groups) but not for depth (averaged across latitudinal groups). Richness varied locally and showed a variety of patterns depending on the areas and depths considered. The greatest diversity of molluscs was found in the fine fraction (i.e.

Connectivity is a key factor in determining the genetic structure of marine populations, and type and duration of the larval phase strongly affect dispersal abilities of species. In Antarctica, invertebrates show a higher proportion of species with limited pelagic dispersal, and any exception to this pattern is worthy of attention. Capulidae is a family of kleptoparasitic gastropods, with two larval strategies. Most species have a peculiar planktotrophic larva, the ‘echinospira’, which enables a long pelagic dispersal; a minority of species undergo lecithotrophic development. We provide the first molecular phylogenetic framework for the family and define the Antarctic species based on molecular data. Based on this information, and on larval shell morphology, we tested the hypothesis that capulid species with high dispersal capacities via planktotrophic larvae display high genetic connectivity over long distances. Our data showed that whilst larval planktotrophy is the predominant larval strategy of the family worldwide, the vast majority of Antarctic species exhibit non-planktotrophic development. The unique exception, Capulus subcompressus, showed high genetic connectivity between the Ross Sea and Weddell Sea-Antarctic Peninsula. In all other Antarctic species, environmental constraints selected towards intracapsular metamorphosis, despite the associated limits of dispersal and finding a host.