Stefano Schiaparelli

The spatial structure of Antarctic biodiversity

Patterns of environmental spatial structure lie at the heart of the most fundamental and familiar patterns of diversity on Earth. Antarctica contains some of the strongest environmental gradients on the planet and therefore provides an ideal study ground to test hypotheses on the relevance of environmental variability for biodiversity. To answer the pivotal question, “How does spatial variation in physical and biological environmental properties across the Antarctic drive biodiversity?” we have synthesized current knowledge on environmental variability across terrestrial, freshwater, and marine Antarctic biomes and related this to the observed biotic patterns. The most important physical driver of Antarctic terrestrial communities is the availability of liquid water, itself driven by solar irradiance intensity. Patterns of biota distribution are further strongly influenced by the historical development of any given location or region, and by geographical barriers. In freshwater ecosystems, free water is also crucial, with further important influences from salinity, nutrient availability, oxygenation, and characteristics of ice cover and extent. In the marine biome there does not appear to be one major driving force, with the exception of the oceanographic boundary of the Polar Front. At smaller spatial scales, ice cover, ice scour, and salinity gradients are clearly important determinants of diversity at habitat and community level. Stochastic and extreme events remain an important driving force in all environments, particularly in the context of local extinction and colonization or recolonization, as well as that of temporal environmental variability. Our synthesis demonstrates that the Antarctic continent and surrounding oceans provide an ideal study ground to develop new biogeographical models, including life history and physiological traits, and to address questions regarding biological responses to environmental variability and change.

Shallow- and deep-water mollusc distribution at Terra Nova Bay (Ross Sea, Antarctica)

Abstract The aim of this work is to improve the knowledge of the mollusc fauna of Terra Nova Bay (Ross Sea), on the basis of more than 100 stations sampled from 25 to 1100 m depth, during Italian Antarctic Expeditions (austral summers 1987/1988, 1989/1990, 1993/1994, 1994/1995, 1995/1996 and 1997/1998). In shallow waters, gastropod fauna is represented by 31 species, among which Neobuccinum eatoni, Onoba gelida, Powellisetia deserta, Philine cf. apertissima and Austrodoris kerguelenensis are the most abundant, while among bivalves (25 species) the commonest species are Adamussium colbecki, Yoldia eightsi, Laternula elliptica and “Montacuta”nimrodiana. At present, most of the Antarctic mollusc species are known as having circumantarctic distribution and are considered eurybathic. Moreover, in general, only scarce data are available on their substrate preferences, because of their occurrence in scattered sampling stations with different sediment features. In the present study carried out at Terra Nova Bay, based on a relatively high number of stations, a clear zonation of mollusc assemblages is shown, according to depth and sediment features. While gastropods characterise the superficial algal belts dominated by the red algae Iridaea cordata and Phyllophora antarctica, bivalve distribution is wider. Adamussium colbecki is the dominant species in the upper 100 m, both on soft and hard bottoms, if the slope is suitable (density up to 40–60 ind./m2). On coarse sands, this species is frequently accompanied by L. elliptica (density <20 ind./m2), while Y. eightsi characterises organic- enriched bottoms (density 70–80 ind./m2). Below 200 m depth Adacnarca nitens, Limatula hodgsoni, “Montacuta”nimrodiana and Mysella gibbosa are commonly found on relatively coarse sediments, while Thyasira dearborni and Yoldiella ecaudata prefer muddy bottoms. In order to identify bivalve assemblages, multivariate analyses were applied to stations grouped into depth ranges, sediment features and location. While shallow bathymetric ranges (25–200 m) are clearly defined, deeper clusters of stations are more influenced by the high degree of eurybathy of most of the species and by the scattered distribution of the sediment particle sizes.

Molecular phylogeny of pontobdelline leeches and their place in the descent of fish leeches (Hirudinea, Piscicolidae)

Phylogenetic relationships of all genera of the fish leech subfamily Pontobdellinae were investigated using mitochondrial (12S rDNA, COI, tRNA‐Leu, ND1) and nuclear (28S rDNA) DNA sequences under maximum likelihood, Bayesian inference and parsimony. All methods resulted in trees that corroborated the monophyly of the family Piscicolidae, but recovered their subfamily Pontobdellinae as non‐monophyletic. Based on the basal position of the giant Antarctic Megaliobdella szidati, it is hypothesized that the putative ancestor of fish leeches was a free‐ranging, large bodied, muscular leech. The next branch contains parasites of cartilaginous fishes, Pontobdella muricata and Pontobdella macrothela. Two remaining genera of the subfamily (the Arctic Oxytonostoma and the Antarctic Moorebdellina) showed weak affinities to other piscicolid taxa. The obtained phylogenetic hypothesis suggests a possible transition from an ancestral free‐ranging life style and temporary parasitism, to parasitism on cartilaginous fishes, followed by parasitism on bony fishes.

Cenozoic evolution of Muricidae (Mollusca, Neogastropoda) in the Southern Ocean, with the description of a new subfamily

Barco, A., Schiaparelli, S., Houart, R. & Oliverio, M. (2012). Cenozoic evolution of Muricidae (Mollusca, Neogastropoda) in the Southern Ocean, with the description of a new subfamily. —Zoologica Scripta, 41, 596–616.

Skin-digging tanaids: the unusual parasitic behaviour of Exspina typica in Antarctic waters and worldwide deep basins

Abstract The order Tanaidacea includes over 1000 species which are mainly free-living or tube-dwelling detritivores. Exspina typica Lang, 1968 represents an exception to these common life styles, having being found in the intestine and body cavity of deep sea holothuroids. The 2008 New Zealand ‘IPY-CAML Cruise’ held in the Ross Sea collected several deepwater holothuroids that were observed to carry specimens of E. typica inside their coelomic cavity. A clear interpretation of this association was hence possible. Even if E. typica shows slight adaptations to a parasitic life style, the tanaids were found to actively ‘dig’ into the hosts skin, grasping tissue with their claws and producing tunnels in the body wall. It is therefore possible to clearly define this association, which is here reported from the Antarctic for the first time, as parasitism.

Influence of rocky substrata on three-dimensional sponge cells model development

Many marine and freshwater organisms are rocky bottom dwellers, and the mineralogical composition of the substratum is known to potentially condition their biology and ecology. In this work, we propose the use of 3D sponge cellular aggregates, called primmorphs, as suitable models for a multidisciplinary study of the mechanisms which regulate the biological responses triggered by the contact with different inorganic substrata. In our experiments, primmorphs obtained from the marine sponge Petrosia ficiformis (Poiret, 1789) were reared on calcium carbonate or on quartzitic substrata, respectively, and their morphological development was described. In parallel, the quantitative expression levels of two genes, silicatein and heat shock protein 70 (HSP70), were evaluated. The first gene is strictly correlated to spiculogenesis and sponge growth, while the second is an important indicator of stress. The results achieved with this in vitro model clearly demonstrate that quartzitic substrata determine the increase of silicatein gene expression, a lower expression of HSP70 gene, and a remarkable difference in primmorphs morphology compared to the analogous samples grown on marble.

Ross Sea Mollusca from the Latitudinal Gradient Program: R/V Italica 2004 Rauschert dredge samples

Abstract Information regarding the molluscs in this dataset is based on the Rauschert dredge samples collected during the Latitudinal Gradient Program (LGP) on board the R/V “Italica” in the Ross Sea (Antarctica) in the austral summer 2004. A total of 18 epibenthic dredge deployments/samplings have been performed at four different locations at depths ranging from 84 to 515m by using a Rauschert dredge with a mesh size of 500μm. In total 8,359 specimens have been collected belonging to a total of 161 species. Considering this dataset in terms of occurrences, it corresponds to 505 discrete distributional records (incidence data). Of these, in order of abundance, 5,965 specimens were Gastropoda (accounting for 113 species), 1,323 were Bivalvia (accounting for 36 species), 949 were Aplacophora (accounting for 7 species), 74 specimens were Scaphopoda (3 species), 38 were Monoplacophora (1 species) and, finally, 10 specimens were Polyplacophora (1 species). This data set represents the first large-scale survey of benthic micro-molluscs for the area and provides important information about the distribution of several species, which have been seldom or never recorded before in the Ross Sea. All vouchers are permanently stored at the Italian National Antarctic Museum (MNA), Section of Genoa, enabling future comparison and crosschecking. This material is also currently under study, from a molecular point of view, by the barcoding project “BAMBi” (PNRA 2010/A1.10).

The Census of Antarctic Marine Life: The First Available Baseline for Antarctic Marine Biodiversity

The Census of Antarctic Marine Life (CAML, www.caml.aq) was a 5-year long international project that focused the attention on the ice-bound oceans of Antarctica during the International Polar Year (IPY) in 2007–08, bringing together researchers from 30 different countries and more than 50 institutions. It was one of the fifteen IPY-endorsed biological projects devoted to Antarctica (Project #83) and coordinated field operations of 18 research voyages in Antarctica during IPY and/or within the CAML life-span.

‘Hitchhiker’ polynoid polychaetes in cold deep waters and their potential influence on benthic soft bottom food webs

Abstract We describe a new association for Antarctica, involving an holothuroid host, Bathyplotes bongraini Vaney, 1914, and a parasitic polynoid polychaete, Eunoe opalina McIntosh, 1885, which lives on the host body. Both species have never been recorded in the study area, the Ross Sea. The ecological definition of this partnership is difficult to assess, being a mix of phoresis, protective association, parasitism and, possibly, kleptocommensalism. Eunoe opalina emerges also as a true predator, ingesting several food items that do not belong to the diet of Bathyplotes. We compare this association with analogous examples known from shallow tropical environments as well as bathyal and abyssal depths. Given the conspicuous similarities between the deep water and high latitude examples of this kind of association, a possible common origin is hypothesized. Although the role of such a kind of parasitic relationships in Antarctic communities remains to be fully evaluated, it seems evident that, at high latitudes, where trophic levels are simplified and food webs do not have much redundancy, the impact of such a ‘multitasking’ predator-parasite as E. opalina might be of a greater magnitude than its shallow water tropical counterpart.

Cross-disciplinarity in the advance of Antarctic ecosystem research

The biodiversity, ecosystem services and climate variability of the Antarctic continent and the Southern Ocean are major components of the whole Earth system. Antarctic ecosystems are driven more strongly by the physical environment than many other marine and terrestrial ecosystems. As a consequence, to understand ecological functioning, cross-disciplinary studies are especially important in Antarctic research. The conceptual study presented here is based on a workshop initiated by the Research Programme Antarctic Thresholds - Ecosystem Resilience and Adaptation of the Scientific Committee on Antarctic Research, which focussed on challenges in identifying and applying cross-disciplinary approaches in the Antarctic. Novel ideas and first steps in their implementation were clustered into eight themes. These ranged from scale problems, through risk maps, and organism/ecosystem responses to multiple environmental changes and evolutionary processes. Scaling models and data across different spatial and temporal scales were identified as an overarching challenge. Approaches to bridge gaps in Antarctic research programmes included multi-disciplinary monitoring, linking biomolecular findings and simulated physical environments, as well as integrative ecological modelling. The results of advanced cross-disciplinary approaches can contribute significantly to our knowledge of Antarctic and global ecosystem functioning, the consequences of climate change, and to global assessments that ultimately benefit humankind.