Because of the unique conditions that exist around the Antarctic continent, Southern Ocean (SO) ecosystems are very susceptible to the growing impact of global climate change and other anthropogenic influences. Consequently, there is an urgent need to understand how SO marine life will cope with expected future changes in the environment. Studies of Antarctic organisms have shown that individual species and higher taxa display different degrees of sensitivity to environmental shifts, making it difficult to predict overall community or ecosystem responses. This emphasizes the need for an improved understanding of the Antarctic benthic ecosystem response to global climate change using a multitaxon approach with consideration of different levels of biological organization. Here, we provide a synthesis of the ability of five important Antarctic benthic taxa (Foraminifera, Nematoda, Amphipoda, Isopoda, and Echinoidea) to cope with changes in the environment (temperature, pH, ice cover, ice scouring, food quantity, and quality) that are linked to climatic changes. Responses from individual to the taxon-specific community level to these drivers will vary with taxon but will include local species extinctions, invasions of warmer-water species, shifts in diversity, dominance, and trophic group composition, all with likely consequences for ecosystem functioning. Limitations in our current knowledge and understanding of climate change effects on the different levels are discussed.

In the Southern Ocean, that is areas south of the Polar Front, long-term oceanographic cooling, geographic separation, development of isolating current and wind systems, tectonic drift and fluctuation of ice sheets amongst others have resulted in a highly endemic benthic fauna,\ud which is generally adapted to the long-lasting, relatively stable environmental conditions. The Southern Ocean benthic ecosystem has been subject to minimal direct anthropogenic impact (compared to elsewhere) and thus presents unique opportunities to study biodiversity and its\ud responses to environmental change. Since the beginning of the century, research under the Census of Marine Life and International Polar Year initiatives, as well as Scientific Committee of Antarctic Research biology programmes, have considerably advanced our understanding of the Southern Ocean benthos. In this paper, we evaluate recent progress in Southern Ocean benthic research and identify priorities for future research. Intense efforts to sample and describe the benthic fauna, coupled with coordination of information in global databases, have greatly enhanced\ud understanding of the biodiversity and biogeography of the region. Some habitats, such as chemosynthetic systems, have been sampled for the first time, while application of new technologies and methods are yielding new insights into ecosystem structure and function. These advances have\ud also highlighted important research gaps, notably the likely consequences of climate change. In a time of potentially pivotal environmental change, one of the greatest challenges is to balance conservation with increasing demands on the Southern Ocean’s natural resources and services. In\ud this context, the characterization of Southern Ocean biodiversity is an urgent priority requiring timely and accurate species identifications, application of standardized sampling and reporting procedures, as well as cooperation between disciplines and nations

There has been a significant body of literature on species flock definition but not so much about practical means to appraise them. We here apply the five criteria of Eastman and McCune for detecting species flocks in four taxonomic components of the benthic fauna of the Antarctic shelf: teleost fishes, crinoids (feather stars), echinoids (sea urchins) and crustacean arthropods. Practical limitations led us to prioritize the three historical criteria (endemicity, monophyly, species richness) over the two ecological ones (ecological diversity and habitat dominance). We propose a new protocol which includes an iterative fine-tuning of the monophyly and endemicity criteria in order to discover unsuspected flocks. As a result nine « full » species flocks (fulfilling the five criteria) are briefly described. Eight other flocks fit the three historical criteria but need to be further investigated from the ecological point of view (here called « core flocks »). The approach also shows that some candidate taxonomic components are no species flocks at all. The present study contradicts the paradigm that marine species flocks are rare. The hypothesis according to which the Antarctic shelf acts as a species flocks generator is supported, and the approach indicates paths for further ecological studies and may serve as a starting point to investigate the processes leading to flock-like patterning of biodiversity.

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Understanding the factors that determine the distribution of taxa at various spatial scales is a crucial challenge in the context of global climate change. This holds particularly true for polar marine biota that are composed of both highly adapted and vulnerable faunas. We analysed the distribution of 2 Antarctic echinoid species, Sterechinus antarcticus and S. neumayeri, at the scale of the entire Southern Ocean using 2 niche modelling procedures. The performance of distribution models was tested with regard to the known ecology of the species. The respective contributions of environmental parameters are discussed along with the putative roles played by biotic interactions and biogeographic processes. Depth was the parameter that contributed most to both distribution models, whereas sea ice coverage and sea surface temperature had significant contributions for S. neumayeri only. Suitability maps of the 2 species were mostly similar, with a few notable differences. The Campbell Plateau and Tasmania were predicted as suitable areas for S. antarcticus only, while S. neumayeri was restricted to the south of the Ant arctic Polar Front. However, numerous sampling data attest that S. antarcticus is absent from the Campbell Plateau and from Tasmania. Different hypotheses are formulated to explain the mismatch between observed and modelled distribution data. They stress the putative roles played by both oceanographic barriers to dispersal (Antarctic Polar Front), biotic factors (species exclusion patterns) and biogeographic processes (ongoing dispersal).KEY WORDS: Habitat suitability map · Sterechinus · Echinoidea · GARP · Maxent · Southern OceanResale or republication not permitted without written consent of the publisher

Mating systems are diverse in animals, notably in crustaceans, but can be inferred from a limited set of parameters. Baeza and Thiel (2007) proposed a model predicting mating systems of symbiotic crustaceans with three host characteristics and the risk of predation. These authors proposed five mating systems, ranging from monogamy to polygynandry (where multiple mating occurs for both genders). Using microsatellite loci, we tested the putatively mating system of the ectoparasite crab Dissodactylus primitivus. We determined the mating frequencies of males and females, parentage assignment (COLONY & GERUD software) as well as the contents of female spermathecae. Our results are globally consistent with the model of Baeza and Thiel and showed, together with previous aquarium experiments, that this ectoparasite evolved a polygamous mating system where males and females move between hosts for mate search. Parentage analyses revealed that polyandry is frequent and concerns more than 60% of clutches, with clutches being fertilized by up to 6 different fathers. Polygyny is supported by the detection of eight males having sired two different broods. We also detected a significant paternity skew in 92% of the multipaternal broods. Moreover, this skew is probably higher than the estimation from the brood because additional alleles were detected in most of spermathecae. This high skew could be explained by several factors as sperm competition or cryptic female choice. Our genetic data, combined with previous anatomic analyses, provide consistent arguments to suggest sperm precedence in D. primitivus.

In many symbioses involving marine crustaceans the nature of the relationships and the population biology remain overlooked, obscuring the understanding of their ecology and evolution. The association between the pea crab Dissodactylus primitivus and the irregular sea urchin Meoma ventricosa was investigated in the Caribbean Sea. The work tested the predictions provided by an evolutionary model, in which host-switching behaviour and polygynandry are expected for the mating system of D. primitivus. The crab prevalence (infected sea urchins) and mean burden were high and variable between sites and/or years. All post-metamorphic stages of crabs were found on the host, and no exclusion effect was observed between juvenile and adult crabs. In adults, although a general 1:1 sex ratio was stable over the years, there was no evidence for social monogamy. Adult males occurred more often on host-harbouring non-ovigerous females, suggesting that they search for females available for mating. This assumption was supported by a recolonization experiment showing that the males move between hosts. However, both juveniles and females also moved between hosts, indicating that this behaviour could occur due to causes other than mate searching. D. primitivus inflicts external lesions on M. ventricosa teguments. The most severe lesions were associated with a lower gonad volume during spawning, suggesting a reduction in fitness of the host. The demography of D. primitivus and the recolonization experiments indicate that the mating system of this crab is the 'pure-search polygynandry of mobile females', but the parasitic nature of the relationship could confound this assumption. KEY WORDS: Parasitism · Mating system · Life cycle · Brachyuran crustaceans · SpatangoidsResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 375: 173-183, 2009 vided empirical support for the model, but they claimed that more case studies are needed to strengthen their model.In crustaceans, as pointed out by Thiel (2000), while many different host -symbiont associations have been described, little is known of the population biology and the nature of the relationship (e.g. mutualism vs. parasitism). Host exploitation will not only depend on mating or social systems of the symbionts, but also on the nature of the symbiotic relationship. For example, a commensal using its host mainly as a shelter or chemical refuge will not exploit it in the same way as a parasite using its host as a food resource. In turn, the nature of host exploitation could influence the social system of the symbiont. For example, in the case of parasitism, host resistance could modulate the number of infecting symbionts, whatever their mating system, and therefore drive their social structure. Thus, knowledge on the nature of the relationship is a prerequisite for understanding symbiosis evolution and ecology.Within the Crustacea, symbiotic relationships involving brachyuran crabs are quite common. Decapod symbionts belong to 7 famili...

The shell of the bivalve Montacuta ferruginosa, a symbiont living in the burrow of an echinoid, is covered with a rust-colored biofilm. This biofilm includes different morphotypes of bacteria that are encrusted with a mineral rich in ferric ion and phosphate. The aim of this research was to determine the genetic diversity and phylogenetic affiliation of the biofilm bacteria. Also, the possible roles of the microorganisms in the processes of mineral deposition within the biofilm, as well as their impact on the biology of the bivalve, were assessed by phenotypic inference. The genetic diversity was determined by denaturing gradient gel electrophoresis (DGGE) analysis of short (193-bp) 16S ribosomal DNA PCR products obtained with primers specific for the domain Bacteria. This analysis revealed a diverse consortium; 11 to 25 sequence types were detected depending on the method of DNA extraction used. Individual biofilms analyzed by using the same DNA extraction protocol did not produce identical DGGE profiles. However, different biofilms shared common bands, suggesting that similar bacteria can be found in different biofilms. The phylogenetic affiliations of the sequence types were determined by cloning and sequencing the 16S rRNA genes. Close relatives of the genera Pseudoalteromonas,Colwellia, and Oceanospirillum (members of the γ-Proteobacteria lineage), as well as Flexibacter maritimus (a member of theCytophaga-Flavobacter-Bacteroides lineage), were found in the biofilms. We inferred from the results that some of the biofilm bacteria could play a role in the mineral formation processes.