Adamussium Research Articles

Detergent-stable proteases from the antarctic scallop Adamussium colbecki

Detergent-stable proteases were found in crude extract of the Antarctic scallop Adamussium colbecki. The results of gelatin zymography indicated the availability of the proteases which able to act in the presence of SDS, whereas plasmin and miniplasmin maintained their activity toward gelatin only after complete removing of detergent. Total proteolytic activity, represented by casein hydrolysis was within the control level after incubation of crude extract with detergents such as Tween 80 and SDS whereas trypsin activity was significantly reduced.

Population Dynamics and Parasite Load of a Foraminifer on Its Antarctic Scallop Host with Their Carbonate Biomass Contributions.

We studied the population dynamics and parasite load of the foraminifer Cibicides antarcticus on its host the Antarctic scallop Adamussium colbecki from three localities differing by sea ice cover within western McMurdo Sound, Ross Sea, Antarctica: Explorers Cove, Bay of Sails and Herbertson Glacier. We also estimated CaCO3 biomass and annual production for both species. Cibicides populations varied by locality, valve type, and depth. Explorers Cove with multiannual sea ice had larger populations than the two annual sea ice localities, likely related to differences in nutrients. Populations were higher on Adamussium top valves, a surface that is elevated above the sediment. Depth did not affect Cibicides distributions except at Bay of Sails. Cibicides parasite load (the number of complete boreholes in Adamussium valves) varied by locality between 2% and 50%. For most localities the parasite load was < 20%, contrary to a previous report that ~50% of Cibicides were parasitic. The highest and lowest parasite load occurred at annual sea ice localities, suggesting that sea ice condition is not important. Rather, the number of adults that are parasitic could account for these differences. Cibicides bioerosion traces were categorized into four ontogenetic stages, ranging from newly attached recruits to parasitic adults. These traces provide an excellent proxy for population structure, revealing that Explorers Cove had a younger population than Bay of Sails. Both species are important producers of CaCO3. Cibicides CaCO3 biomass averaged 47-73 kg ha-1 and Adamussium averaged 4987-6806 kg ha-1 by locality. Annual production rates were much higher. Moreover, Cibicides represents 1.0-2.3% of the total host-parasite CaCO3 biomass. Despite living in the coldest waters on Earth, these species can contribute a substantial amount of CaCO3 to the Ross Sea and need to be incorporated into food webs, ecosystem models, and carbonate budgets for Antarctica.

ALPHA AND BETA DIVERSITY OF FORAMINIFERA THAT ENCRUST THE ANTARCTIC SCALLOP ADAMUSSIUM COLBECKI: ECOLOGICAL CONNECTIVITY AMONG SHELLS AND BETWEEN SITES

Benthic foraminifera are ubiquitous marine organisms in Antarctica, but little is known about their ecology despite their importance as climate-change proxies. A fundamental question remains unanswered: is foraminiferal diversity highly localized and similar to reports for Antarctic benthic invertebrates? If so, high endemism would result driven by dispersal limitation with little connectivity among sites. To answer this question, the composition, abundance, spatial distribution and alpha (α) and beta (β) diversity of foraminiferal species that encrust living shells of the Antarctic scallop Adamussium colbecki were compared within and between two sites located 30-km apart in McMurdo Sound, Ross Sea, Antarctica: Bay of Sails (BOS), an open coastal region with annual sea-ice cover, and Explorers Cove (EC), a protected embayment with multiannual sea-ice cover. Foraminiferal community structure differed between the sites, generated by variations in species abundance, turnover of rare species, and heterogeneity in species composition between top and bottom valves. Foraminifera were significantly more common on the scallop’s auricles, perhaps driven by nutrients generated by the scallop. Calcareous taxa were significantly more abundant at EC despite lower seawater pH, while agglutinated taxa were significantly more abundant at BOS. Alpha diversity (species richness, Shannon H , e H ) was higher at BOS than at EC and is similar to deep-sea diversity reported for Caribbean encrusting foraminifera. Based on Shannon H , foraminifera at EC may represent a stressed community dominated by Cibicides antarcticus , while those at BOS may represent a transitional community. Within-site β-diversity was high, spurred by the turnover of rare species between top and bottom valves, which acted as separate microhabitats. Higher β-diversity at BOS suggests that foraminiferal dispersal and recruitment were more localized than at EC. Additive partitioning revealed that encrusting diversity was mostly held at the local level, and that BOS and EC have high connectivity, similar to deep-sea communities. The Antarctic endemicity of these protists is questionable, and is in stark contrast to Antarctic invertebrates with high within- and between-site diversity. Therefore, Antarctic encrusting foraminifera appear to be influenced primarily by niche-based processes, rather than dispersal limitation. Indeed, habitat islands, such as carbonate shells, are essential for generating Antarctic diversity, and are integral for the conservation of Antarctica’s unique polar ecosystem.

Antarctic seawater temperature evaluation based on stable isotope measurements on Adamussium colbecki shells: kinetic effects vs. isotopic equilibrium

A year-long controlled growth experiment of 60 specimens of the Antarctic bivalve Adamussium colbecki was conducted in Terra Nova Bay (Ross Sea) to evaluate its reliability as a suitable archive of water mass properties. Nine shells were sub-sampled for stable oxygen and carbon isotope analysis to study the inter and intra specimen variations. Slow-growing A. colbecki precipitate their calcitic shells close to the expected oxygen and carbon isotopic equilibrium, whereas the fast-growing individuals are strongly influenced by biogenetic and kinetic effects. The equation of Kim and O'Neil (1997) is considered a fair approximation for the δ18O-temperature relationship in slow-growing individuals. The reconstructed temperature is closer to the mean experimental summer temperature than the annual one. This fact is interpreted as reflecting a possible winter decrease of shell growth, the salinity variation and the corrections for negative temperature on calibrating the δ18O-temperature relationship. Our results support the hypothesis that A. colbecki might represent a good archive for encoding Antarctic Shelf water summer temperature information. Further improvements in adopting A. colbecki as a paleotemperature archive will require the evaluation of the seasonal variability in shell growth rate through culturing slow-growing A. colbecki individuals at near-freezing temperatures to calibrate a species-specific δ18O-temperature equation.

Addendum to “A new Antarctic certified reference material for trace elements: Adamussium colbecki” by Sergio Caroli and Paola Bottoni [Microchem. J., Vol. 96 (2010), 190–193

Addendum to “A new Antarctic certified reference material for trace elements: Adamussium colbecki” by Sergio Caroli and Paola Bottoni [Microchem. J., Vol. 96 (2010), 190–193

Experimental growth pattern calibration of Antarctic scallop shells ( Adamussium colbecki, Smith 1902) to provide a biogenic archive of high-resolution records of environmental and climatic changes

To determine the potential of Antarctic bivalve shells as biomonitors for environmental and climatic variations in polar marine areas, we developed a growth model for juvenile Adamussium colbecki Smith, 1902 based on the use of in situ temporal calcein markings to calibrate growth patterns in the external striae formation. To minimize scallop stress caused by excessive handling, in situ benthic chambers were used for the marking experiment, during an exposure time of 6 h. Once marked, scallops remained on site in a benthic cage and were collected 18, 26, and 41 days later. Apart from a few specimens affected by possible calcein toxicity effects, the detectable mark in all shells revealed a higher austral summer growth rate for A. colbecki compared to other Antarctic bivalves. Using calcein labeling, we identified a near 14-day periodicity in the striae formation associated with the fortnightly seawater level regime. Striae counting and increment width measurements showed an annual cycle, with no clear cessation of growth in juvenile specimens, allowing age determination. Because of the relatively high growth rate for a polar species and easily recognizable sclerochronological calendar in the shell striae formation, A. colbecki is an appropriate species for high-resolution (infra-monthly) geochemical sampling. Comparison between LA-ICP-MS analyses (Li, B, Mg, Mn, Co, Sr, Ba, Pb) from one shell and hydrological parameters (sea level, temperature, salinity) measured in seawater suggests, however, that more work is needed to calibrate the trace element proxies. Nevertheless, the shell of the Antarctic scallop A. colbecki has tremendous potential for recording environmental conditions from time periods covering months to a few years in polar waters, notably the ice melting date.

Non-chromatographic screening method for the determination of mercury species. Application to the monitoring of mercury levels in Antarctic samples

A simple non-chromatographic method for the determination of mercury (Hg 2+), methylmercury (MeHg +), dimethylmercury (Me 2Hg), and phenylmercury (PhHg +) employing atomic fluorescence spectrometry (AFS) as detection technique was developed. Mercury species showed a particular behavior in the presence of several reagents. In a first stage SnCl 2 was employed for Hg 2+ determination; in a second step, [Hg 2+ + PhHg +] concentration was determined using SnCl 2 and UV radiation. MeHg + decomposition was prevented adding 2-mercaptoethanol. In a third stage, [Hg 2+ + PhHg + + MeHg +] concentration was determined using K 2S 2O 8. Finally, the four species were determined employing NaBH 4. Reagents concentration and flow rates were optimized. The extraction technique of mercury species involved the use of 2-mercaptoethanol as ion-pair reagent. The limits of detection for Hg 2+, PhHg +, MeHg +, and Me 2Hg were 1, 40, 68, and 99 ng L −1 with a relative standard deviation of 1.5, 3.1, 4.7 and 5.8%, respectively. Calibration curve was linear with a correlation factor equal to 0.9995. The method was successfully applied to the determination of the mercury species in two Antarctic materials: IRMM 813 ( Adamussium colbecki) and MURST-ISS-A2 ( Antarctic Krill).

A new Antarctic certified reference material for trace elements: Adamussium colbecki

The certification of a new reference material for trace elements based on the Antarctic bivalve Adamussium colbecki is reported. This certified reference material (CRM), labelled IRMM 813, was produced in the frame of the Italian National Program for Research in Antarctica (Programma Nazionale di Ricerca in Antartide, PNRA). About 40 kg of the scallop were collected at Terra Nova Bay (Ross Sea). The raw material was freeze-dried, jet-milled and homogenized so as to make it suitable for certification. The elements selected for the certification project were As, Cd, Cu, Cr, Fe, Mn, Ni and Zn. Homogeneity and short- and long-term stability were preliminarily investigated so as to assess the suitability of the freeze-dried mass as a candidate CRM. The candidate material was found to be fit for purpose, thus allowing the following phases of the certification project to be undertaken, in the first place the selection of expert laboratories for the accomplishment of the certification campaign. Eighteen laboratories from twelve countries accepted to participate in the certification project which thus could be successfully completed.

Video observations on non-swimming valve claps in the Antarctic scallop Adamussium colbecki

Video observations on non-swimming valve claps in the Antarctic scallop <i>Adamussium colbecki</i>

Epibiotic demosponges on the Antarctic scallop Adamussium colbecki (Smith, 1902) and the cidaroid urchins Ctenocidaris perrieri Koehler, 1912 in the nearshore habitats of the Victoria Land, Ross Sea, Antarctica

The importance of epibiosis in Antarctic benthic communities is highlighted here considering the specific diversity of sponges living on shells of the scallop Adamussium colbecki and on spines of the cidaroid urchin Ctenocidaris perrieri. Scallops are from three different areas along the Victoria Land [Tethys Bay (TB), New Harbour (NH), Dunlop Island (DI)], while cidaroid urchins are from NH but not present in the two other stations. Homaxinella balfourensis is the commonest species both on the scallops and cidaroid urchins. Other common species on scallops are Myxilla (Myxilla) asigmata, Lissodendoryx (Ectyodoryx) nobilis and Iophon unicorne at NH, Iophon unicorne at DI, and Iophon radiatum, Haliclona sp. 1, Iophon unicorne and Lissodendoryx (Ectyodoryx) nobilis at TB. The highest number of sponge species we found on a single scallop was ten and the sample was collected at NH. On the spines of C. perrieri, Isodictya erinacea, Iophon unicorne and Haliclona (Rhizoniera) dancoi are present too. A. colbecki and C. perrieri, generally living on soft bottoms, represent important substrata for several sponge species. In this way, sponges may increase their dispersal exploiting valves and spines as stepping stones.

Cholinesterases in the Antarctic scallop Adamussium colbecki: Characterization and sensitivity to pollutants

Antarctica is affected by man-made contamination and development of sensitive ecotoxicological tools for impact assessment is a priority task. The aims of the present study were to characterize cholinesterase (ChE) activities in an Antarctic key species, the scallop Adamussium colbecki, and to investigate their sensitivity as biological markers (biomarkers) of exposure to pollutants and of their effects. Our results show that ChEs in gills share most characteristics with true acetylcholinesterase. The present results show that ChE activities in A. colbecki are significantly inhibited by organophosphates (OPs) and somehow affected by in vitro exposure to mixtures of marine contaminants such as polycyclic aromatic hydrocarbons (PAHs), even if no concentration-dependent pattern of response was observed and no effect was elicited by polychlorinated biphenyls (PCBs). The present results do not demonstrate ChEs in A. colbecki as sensitive tools to measure exposure to the above chemicals, but they may be worthy of further study considering the importance of the scallop in Antarctic marine ecosystems and its suitability as a sentinel species.

TROPHIC STRUCTURE OF COASTAL ANTARCTIC FOOD WEBS ASSOCIATED WITH CHANGES IN SEA ICE AND FOOD SUPPLY

Predicting the dynamics of ecosystems requires an understanding of how trophic interactions respond to environmental change. In Antarctic marine ecosystems, food web dynamics are inextricably linked to sea ice conditions that affect the nature and magnitude of primary food sources available to higher trophic levels. Recent attention on the changing sea ice conditions in polar seas highlights the need to better understand how marine food webs respond to changes in such broad-scale environmental drivers. This study investigated the importance of sea ice and advected primary food sources to the structure of benthic food webs in coastal Antarctica. We compared the isotopic composition of several seafloor taxa (including primary producers and invertebrates with a variety of feeding modes) that are widely distributed in the Antarctic. We assessed shifts in the trophic role of numerically dominant benthic omnivores at five coastal Ross Sea locations. These locations vary in primary productivity and food availability, due to their different levels of sea ice cover, and proximity to polynyas and advected primary production. The delta15N signatures and isotope mixing model results for the bivalves Laternula elliptica and Adamussium colbecki and the urchin Sterechinus neumeyeri indicate a shift from consumption of a higher proportion of detritus at locations with more permanent sea ice in the south to more freshly produced algal material associated with proximity to ice-free water in the north and east. The detrital pathways utilized by many benthic species may act to dampen the impacts of large seasonal fluctuations in the availability of primary production. The limiting relationship between sea ice distribution and in situ primary productivity emphasizes the role of connectivity and spatial subsidies of organic matter in fueling the food web. Our results begin to provide a basis for predicting how benthic ecosystems will respond to changes in sea ice persistence and extent along environmental gradients in the high Antarctic.

The phylogeny of native and exotic scallops cultured in China based on 16S rDNA sequences

Scallops of the Family Pectinidae are a valuable resource in marine industry of the world. Understanding the phylogeny of the family is important for the development of the industry. In this study, partial 16S mitochondrial rDNA genes were obtained from 8 scallop species that are commonly cultured indigenous and transplanted species in China. Phylogenetic relationships of Pectinidae were analyzed based on the 8 sequences and other 5 published ones in GenBank, representing 9 genera of the family. The molecular phylogeny trees were constructed using 3 methods with software PHYLIP. The results showe that total 13 species of scallops clustered in 4 clades. Pecten maximus joins P. jacobaeus then Amusium pleuronectes in cluster, indicating close relationship of genus Amusium with Pecten in evolution. P. yessoensis is close to Chlamys farreri and C. islandica. No enough material was available to single out genus Patinopecten as an independent monophyletic subfamily. The position of Adamussium colbecki indicates that it is far from genus Pecten but near to genus Chlamys in evolution.

COLD SCALLOPS RELY ON RUBBER

![Figure][1] Scallops are one of the few bivalve molluscs that can swim. They are not graceful and they are not fast, but they can move when threatened. While temperate and tropical scallops are only just able to swim in warm waters, it is remarkable that Antarctic scallops manage at all in

Exchange between populations of Adamussium colbecki (Mollusca: Bivalvia) in the Ross Sea

The endemic Antarctic scallop Adamussium colbecki (Mollusca: Bivalvia) represents a key species in the Ross Sea littoral benthic ecosystem, locally reaching very high densities. This species has an annual gametogenic cycle, with a summer spawning event, and a pelagic larval behaviour. This paper aims at describing population structure and genetic polymorphism (using AFLP) of the large populations inhabiting the Ross Sea (Terra Nova Bay and McMurdo Sound) in order to investigate possible genetic exchange between A. colbecki in these areas. In Terra Nova Bay, size-frequency distributions show, generally, the dominance of large individuals, although site related differences are found in the abundance of smaller size classes (less than 40 mm), suggesting that recruitment is not a regular event. All McMurdo sites are characterized by large individuals and, at least during this sampling period, recruitment is completely absent. Nuclear DNA analyses show that the largest differences are found at the largest scale (between McMurdo Sound and Terra Nova Bay), but all populations sampled, even at a smaller spatial scale, have a well-settled genetic structure, notwithstanding the pelagic larval strategy. The panmixia hypothesis has therefore to be rejected for this species.

Very slow development in two Antarctic bivalve molluscs, the infaunal clam Laternula elliptica and the scallop Adamussium colbecki

Embryos of the large infaunal clam Laternula elliptica and the scallop Adamussium colbecki, from Antarctica, were cultured over an 18-month period. Their development rates were extremely slow, taking 240 and 177 h, respectively, to reach the trochophore stage. This is ×4 to ×18 slower than related clams and scallops from temperate latitudes. The relationship between temperature and development rate for bivalve molluscs shows the expected slowing with reduced temperature (Q 10 in the range 2–4) for temperate and tropical species. However, the slowing at polar latitudes is much stronger than at warmer waters, and all of the limited data for Antarctic species are well above the Arrhenius plot for the overall bivalve data, and the Q 10 value for Antarctic to cool temperate species is 11.8, well outside the expected range for biological systems. Either the relationships describing the effects of temperature on the kinetics of biological systems do not apply to Antarctic bivalve molluscs, or some other factor that cannot be compensated for becomes important at low temperature. In the laboratory, L. elliptica embryos stayed viable in very sticky egg capsules for up to 18 months without hatching. However, even the disturbance of removing eggs using a pipette ruptured some egg capsules allowing embryo release. Gametogenesis in Antarctic marine invertebrates is almost universally slowed compared to temperate species, with nearly all cases documented requiring more than 1 year to complete oogenesis. The only exception so far appears to be A. colbecki, which has a 1-year gametogenic cycle. The data here indicate that it has been unable to adapt embryonic development in a similar way, and we are not aware of any exceptions to the markedly slowed development at low temperature rule.

Epibionts of the scallop Adamussium colbecki (Smith, 1902) in the Ross Sea, Antarctica

Although it is characterized by a patchy distribution, Adamussium colbecki is considered the most important bivalve of Antarctica, mainly in relation to its functional role in the transfer of energy from the water column to the benthos. Here, we compare the epibionts of A. colbecki from three different areas, highlighting the importance of their shells as a natural secondary hard bottom for many taxa. In this way, we show that due to its ability to swim, the scallop may contribute to the dispersion of epibiotic species, and this probably increases their survival. These data amplify the ecological roles of A. colbecki, which, along with its shells, can be considered an important ecosystem engineer in Antarctic communities.

Organophosphate-resistant forms of acetylcholinesterases in two scallops—the Antarctic Adamussium colbecki and the Mediterranean Pecten jacobaeus

We describe the acetylcholinesterase polymorphisms of two bivalve molluscs, Adamussium colbecki and Pecten jacobaeus. The research was aimed to point out differences in the expression of pesticide-resistant acetylcholinesterase forms in organisms living in different ecosystems such as the Ross Sea (Antarctica) and the Mediterranean Sea. In A. colbecki, distinct acetylcholinesterase molecular forms were purified and characterized from spontaneously soluble, low-salt-soluble and low-salt-Triton extracts from adductor muscle and gills. They consist of two non-amphiphilic acetylcholinesterases (G 2, G 4) and an amphiphilic-phosphatidylinositol-membrane-anchored form (G 2); a further amphiphilic-low-salt-soluble G 2 acetylcholinesterase was found only in adductor muscle. In the corresponding tissues of P. jacobaeus, we found a non-amphiphilic G 4 and an amphiphilic G 2 acetylcholinesterase; amphiphilic-low-salt-soluble acetylcholinesterases (G 2) are completely lacking. Such results are related with differences in cell membrane lipid compositions. In both scallops, all non-amphiphilic AChEs are resistant to used pesticides. Differently, the adductor muscle amphiphilic forms are resistant to carbamate eserine and organophosphate diisopropylfluorophosphate, but sensitive to organophoshate azamethiphos. In the gills of P. jacobaeus, amphiphilic G 2 forms are sensitive to all three pesticides, while the corresponding forms of A. colbecki are sensitive to eserine and diisopropylfluorophosphate, but resistant to azamethiphos. Results indicate that organophosphate and/or carbamate resistant AChE forms are present in species living in far different and far away environments. The possibility that these AChE forms could have ensued from a common origin and have been spread globally by migration is discussed.

Karyology of the Antarctic scallop Adamussium colbecki, with some comments on the karyological evolution of pectinids

Karyotype, location of the nucleolar organiser region (NOR) and heterochromatin presence and composition were studied in the Antarctic scallop Adamussium colbecki Smith, 1902. The karyotype exhibits 2n = 38 chromosomes with 11 pairs of metacentrics, 5 of submetacentrics, one subtelocentric and two telocentrics. Ag-NOR, CMA(3), DA/MM and NOR-FISH evidenced paracentromeric NORs on the short arm of 2nd pair chromosomes. Digestion with three restriction endonucleases followed by sequential staining with Giemsa, CMA(3) and DAPI evidenced on all chromosomes centromeric heterochromatin positive for both DAPI and CMA(3). In situ hybridisation analysis showed the presence of an AT-rich satellite DNA in the centromeric heterochromatin of several chromosomes. A mosaicism was detected in the germinal cell lines of one specimen, as in six of the 20 plates examined the set had 37 chromosomes with a missing pair of telocentrics and an unpaired metacentric. Comparison of the chromosome sets of all the pectinids studied to date and comparison with a phyletic tree obtained from molecular mitochondrial genes studies yielded good agreement between karyotype morphology and taxonomic classification.

A reassessment of the distribution of the common Antarctic scallop Adamussium colbecki (Smith, 1902)

The bivalve Adamussium colbecki is an endemic Antarctic pectinid that can be locally abundant in nearshore habitats, sometimes as the dominant species. However, its distribution around the Antarctic continent is rather puzzling, because it has a disjunct distribution, only occurring at some shallow, nearshore sites. Furthermore, there are some records of living specimens from the deeper shelf. In order to understand the biogeography of this circum-Antarctic species, we critically reviewed literature data on its distribution, comparing the available habitat information for those sites that have the most conspicuous populations of A. colbecki. We identified some major types of environments suitable for this species; these environments, notwithstanding an apparent dissimilarity (e.g., in the trophic conditions), all share a good level of environmental “stability”. In shallow, nearshore areas, these environments are represented by calm hydrographical settings with permanent or persistent sea-ice coverage, while on the shelf, by areas with infrequent iceberg scouring without structured communities of suspension feeders.