Soft Tissues Of Mussels Research Articles

Marine mussel adhesion: biochemistry, mechanisms, and biomimetics

Common blue mussel (Mytilus edulis) is a sessile organism that has unique ability to attach to a wide array of organic and inorganic marine surfaces using its holdfast structures. Strong adhesion to surfaces is essential for mussel survival, movement, and self-defense. Mussel proteins from byssal thread are structural components connecting soft mussel tissues to marine surfaces via an adhesive plaque in the distal end, while adhesive proteins from byssal plaque are responsible for mussel adhesion. Adhesive proteins are small molecules containing a high proportion of post-translationally modified amino acids such as 3,4-dihydroxyphenylalanine (DOPA). High DOPA content, small molecular size, protein flexibility, the presence of metal ions, and a high oxidation state enable strong mussel adhesion to surfaces. Mussel adhesion mechanisms depend on the composition and interactions of mussel proteins, as well as their interactions with the environment. Difficulties in the extraction of mussel adhesion proteins hamper mechanism studies and their practical applications. Development of recombinant mussel proteins and biomimetics will advance our understanding of adhesion mechanisms. In this paper, recent advances in the characterization of mussel adhesive proteins (MAPs), mussel adhesion mechanisms, application of MAPs, and the development of biomimetic biopolymers are reviewed.

Metal accumulation in sediments and biota in Malta Reservoir (Poland)

AbstractMunicipal water reservoirs improve urban landscape architecture, providing water for various domestic uses. At the same time, they are under strong human impact affecting water quality and biological conditions. We investigated the level of metal accumulation (Cd, Co, Cr, Cu, Fe, Ni, Mn, Pb and Zn) in sediments as well as mussels Anodonta anatina and Unio tumidus and common reed Phragmites australis collected from 8 sampling sites at Malta Reservoir (Poznań, Poland) just before the complete drainage of the lake in November, 2012. In all investigated samples metal concentrations ranked in decreasing order: Fe>Mn>Zn>Cu>Cr>Ni>Pb>Co>Cd. Accumulation of toxic metals in roots of P. australis was higher than in soft tissues of mussels although it did not exceed phytotoxic levels. Roots of P. australis accumulated high levels of Cr (mean 9.7 μg g-1) and Ni (mean 5.7 μg g-1). U. tumidus accumulated higher concentrations of Cr (mean 1.1 μg g-1) than A. anatina indicating potential use in bioindication of this metal. The present study provides the most recent information on metal content in sediments and biota in Malta Reservoir and, further, suggests that this reservoir is capable of accumulating toxic elements from preceding water bodies (Lake Swarzędz) and surrounding residential areas.

Some features of the trace metal biogeochemistry in the deep-sea hydrothermal vent fields (Menez Gwen, Rainbow, Broken Spur at the MAR and 9°50′N at the EPR): A synthesis

Along with summarizing the published literature and our own data some new results on properties of the trace metal biogeochemistry in the deep-sea hydrothermal ecosystems at the Mid-Atlantic Ridge (MAR) and East Pacific Rise (EPR) are shown. Differences in mean concentrations of big group of trace metals (Fe, Mn, Zn, Cu, Ni, Cr, Co, As, Pb, Cd, Ag, Hg) between the biotope water of the low- and high-temperature hydrothermal vent fields were firstly revealed. The same trace metals were studied in different groups of organisms within different temperature zones at one and the same vent field (9°50′N EPR), as well as in fauna inhabiting geochemically different vent sites. Distribution patterns of Fe, Mn, Zn, Cu, Cd, Pb, Ag, Ni, Cr, Co, As, Se, Sb, and Hg in different taxa gave an evidence of the influence of environmental and biological parameters on their bioaccumulation in organisms. Among the animals a particular “champion” with respect to the trace metal content was found to be a polychaeta Alvinella pompejana that inhabits the hottest places of the vent sulfide chimneys of the 9°50′N field, EPR. New data on the trace metal distribution between soft tissues and carbonate shell let us estimate a role of biomineralization in the accumulation of metals in the Bathimodiolus mussels. Contrasting geochemical behavior was revealed for Cu that is enriched in soft tissues of mussels and depleted in shells, on the one hand, and Mn that is accumulated almost totally in mussel shells, on the other hand.Deep-sea hydrothermal biological communities demonstrate a strong concentration function, and bioconcentration factors (BCF) of trace metals estimated for Bathimodiolus mussels collected at the four hydrothermal fields vary within the limits of n102–n105 and are similar to that of the littoral mussels. Due to this and to the high values of biomasses per square meter, the hydrothermal fauna may be considered as a newly discovered biological filter of the oceans.

Comparison of Bioaccumulation and Biomarker Responses in Dreissena polymorpha and D. bugensis After Exposure to Resuspended Sediments

The zebra mussel Dreissena polymorpha is widely used as sentinel organism for the assessment of environmental contamination in freshwater environments. However, in the River Rhine (Germany), the D. polymorpha population is declining, whereas the closely related quagga mussel D. bugensis is found in high numbers at some sites. In the present laboratory study, D. polymorpha and D. bugensis were exposed to resuspended native sediments for ≤2 weeks. Wet sediments (<63μm, 100mgl(-1) dry weight) were used as surrogate suspended particulate matter to mimic one of the mussels' main uptake route for chemicals. The sediments were sampled in (1) the River Elbe in Dessau, a site known to be highly polluted with, e.g., organochlorine (OC) pesticides and (2) at a relatively unpolluted site in Havelberg in the River Havel, one of the Elbe's tributaries. Chemical analysis of persistent OC compounds (seven polychlorinated biphenyls [PCBs], DDT and its metabolites (DDX), hexachlorocylohexanes [HCHs], and hexachlorobenzene [HCB]) in soft tissue of mussels showed significantly greater values of PCBs 101, 118, 153, 138, 180, the sum of seven PCBs, and p,p'-DDD in D. bugensis compared with D. polymorpha. Fourteen days of exposure to Dessau sediment increased the concentration of p,p'-DDE and p,p'-DDD, as well as the sum of DDX, in both species compared with Havelberg sediment. Interspecific differences were less pronounced when regarding chemical concentrations with lipid content instead of dry-weight of tissue because D. bugensis had greater levels of total lipid than D. polymorpha. DNA damage in gills, as measured with the comet assay, was greater in D. bugensis compared with D. polymorpha. Simultaneously, the content of heat-shock protein (hsp70) in gills was greater in D. polymorpha than in D. bugensis. DNA damage and hsp70 were not induced by exposure time or sediment type. This study shows that D. bugensis and D. polymorpha may differ in their bioaccumulation potential of OC pesticides as well as their levels of DNA damage and hsp70. Therefore, more investigations are needed before quagga mussel can be used as alternative test organism for the zebra mussel.

DEVELOPMENT OF A CHEMILUMINESCENT ELISA FOR DETERMINING OKADAIC ACID IN SHELLFISH

ABSTRACTAn indirect competitive enzyme‐linked immunosorbent assay with chemiluminescent (CL‐ELISA) detection for okadaic acid (OA) in mussel muscle was developed. A hybridoma cell line secreting monoclonal antibody against OA was established after immunization of BALB/c mice with artificially synthesized OA‐bovine serum albumin as antigen. Luminol solution was used as the substrate for horseradish peroxidase. The detection limit was 0.175 ng/g. The range of average fortified recovery was 91.8–102.6% when OA was spiked in mussel muscle at levels of 50, 160 and 800 µg/kg. The standard curve for OA showed good linearity over the concentration range of 0.08125–20 ng/mL. The cross‐reactivity with dinophysistoxin1 and saxitoxin was 51.82 and 0%, respectively. In a residue study, the results obtained by CL‐ELISA correlated well within those obtained using the commercial ABRAXIS kit (ABRAXIS, Warminster, PA). The developed method is therefore suitable for detecting the residues of OA in shellfish.PRACTICAL APPLICATIONSDiarrhetic shellfish poisoning is a gastrointestinal syndrome that occurs in humans following the consumption of bivalve mollusks contaminated with OA with the main symptoms of diarrhea, nausea, vomiting and abdominal pain. OA widely exists at marine products and it is very important to develop a technique to monitor this toxin. In this study, a sensitive competitive indirect enzyme‐linked immunosorbent assay with chemiluminescence for determination of OA in mussel soft tissues was investigated. Chemiluminescent ELISA (CL‐ELISA) is a good alternative method for screening samples. This technique has the potential to improve the sensitivity of the immunoassays by at least two to three orders of magnitude compared with conventional colorimetric detection.

Health risks of heavy metals in the mediterranean mussels as seafood

In recent years, mussels have already become commercially important seafood species worldwide. Mussels accumulate a wide range of metals in their soft tissue. Thus, the determination of accumulated concentrations of heavy metals, such as Pb, Cd, Hg, and As, in mussels is essential because of their usage as seafood and the potential adverse effects of their consumption on human health. In this review, these issues are presented and discussed using the Mediterranean mussel Mytilus galloprovincialis as an example. M. galloprovincialis is very efficient at converting low value victuals into high quality animal protein. The production of M.galloprovincialis in Mediterranean countries has been increasing rapidly, but Spain is still the largest producer of mussels. Only China has a larger production of these mussels than Spain. M. galloprovincialis is a filter feeding animal and accumulates a wide range of metals from their environment. The metal concentrations in the soft tissue of M.galloprovincialis are indicators of marine ecosystems contamination. In the same time, the bioaccumulation of heavy metals remains an issue concerning the consumption of mussels. Thereby, the Cd, Pb, Hg, and As concentration measurement in mussel soft tissue as a seafood have become significant. A review of literature data revealed large variations in the Cd, Pb, Hg, and As concentrations in M. galloprovincialis from their endemic areas, e.g., Mediterranean, Adriatic, and Black Sea, and the concentrations of these toxic metals were generally in the following order: As > Pb > Cd > Hg. The guidelines on heavy metals for seafood safety set by different countries and associations are reviewed. Comparison of the published data with European legislation showed that the levels of the heavy metals generally did not exceed the existing limits in all the mussels analyzed, excluding mussels from hot spots, such as lagoons and harbors, in the Mediterranean, Adriatic, and Black Sea.

PAH body burden and biomarker responses in mussels (Mytilus edulis) exposed to produced water from a North Sea oil field: Laboratory and field assessments

In order to study the impact of produced water (PW) from a North Sea oil field on blue mussels (Mytilus edulis), chemical and biological markers were selected. A laboratory exposure (0.125%, 0.25% and 0.5% of PW) and a field study (6 stations 0.2–2km from a PW discharge point) were conducted. In the laboratory study, PAH bioaccumulation increased in mussel soft tissue even at the lowest exposure dose. Micronuclei frequency demonstrated a dose–response pattern, whereas lysosomal membrane stability showed tendency towards a dose–response pattern. The same markers were assessed in the field study, biomarker analyses were consistent with the contamination level, as evaluated by mussel polycyclic aromatic hydrocarbons body burden. Overall, obtained results confirmed the value of an ecotoxicological approach for a scientifically sound characterisation of biological effects induced by offshore oilfield operational discharges.

Early genotoxic effects in gill cells and haemocytes of Dreissena polymorpha exposed to cadmium, B[ a]P and a combination of B[ a]P and Cd

The aim of this study was to assess the genotoxic potential of environmentally relevant concentrations of Cd on the zebra mussel, an important freshwater sentinel organism, and to determine the stability of DNA damage in gill cells and haemocytes. The oxidative DNA damage and the co-genotoxicity of Cd in combination with B[ a]P were investigated. We measured DNA damage in haemocytes and gill cells of zebra mussels exposed for 11 days to a constant concentration of Cd (10 μg/L), B[ a]P (10 μg/L) or the two combined chemicals (10 μg/L + 1 μg/L). Enzymatic dissociation of gills with dispase gave the lower percentage DNA in tail, compared with collagenase/dispase or collagenase. Bioaccumulation of cadmium in the soft tissues of mussels exposed to CdCl 2 or CdCl 2 + B[ a]P increased in a time-dependent manner indicating that both exposures were effective. Cd (10 μg/L) is genotoxic only during the first 3 days of exposure in gill cells, while in haemocytes the genotoxicity of Cd was observed later. B[ a]P (10 μg/L) induced an early increase of DNA damage in gill cells (after 10 h and 1 day), while in both gill cells and haemocytes, B[ a]P caused a marked increase of DNA damage after 3 days of exposure. The Cd + B[ a]P mixture decreased the DNA-damaging effect of Cd and B[ a]P in both cell types. Cd induced an increase of DNA damage in Fpg-treated slides, indicating that Cd contributed to oxidative DNA damage. Cadmium induced a cytogenetic effect in gill cells, assessed by the number of micronuclei, throughout the duration of the exposure, while B[ a]P did not induce any cytogenetic effect. B[ a]P, Cd and Cd + B[ a]P induced a transient increase in the number of bi-nucleated cells. Our data clearly show that gills are more sensitive to Cd and B[ a]P, which makes them more suitable for future bio-monitoring studies.

A proteomic study using zebra mussels ( D. polymorpha) exposed to benzo(α)pyrene: The role of gender and exposure concentrations

It has recently been established that the use of proteomics can be a useful tool in the field of ecotoxicology. Despite the fact that the mussel Dreissena polymorpha is a valuable bioindicator for freshwater ecosystems, the application of a proteomic approach with this organism has not been deeply investigated. To this end, several zebra mussel specimens were subjected to a 7-day exposure of two different concentrations (0.1 and 2 μg L −1) of the model pollutant benzo[α]pyrene (B[α]P). Changes in protein expression profiles were investigated in gill cytosolic fractions from control/exposed male and female mussels using 2-DE electrophoresis. B[α]P bioaccumulation in mussel soft tissue was also assessed to validate exposure to the selected chemical. We evaluated overall changes in expression profiles for 28 proteins in exposed mussels, 16 and 12 of which were, respectively, over- and under-expressed. Surprisingly, the comparative analysis of protein data sets showed no proteins that varied commonly between the two different B[α]P concentrations. Spots of interest were manually excised and analysed by MALDI-TOF/TOF mass spectrometry. The most significant proteins that were identified as altered were related to oxidative stress, signal transduction, cellular structure and metabolism. This preliminary study indicates the feasibility of a proteomic approach with the freshwater mussel D. polymorpha and provides a starting point for similar investigations. Our results confirm the need to increase the number of invertebrate proteomic studies in order to increase the following: their representation in databases and the successful identification of their most relevant proteins. Finally, additional studies investigating the role of gender and protein modulation are warranted.

Retention of N and P by zebra mussels (Dreissena polymorpha Pallas) and its quantitative role in the nutrient budget of eutrophic Lake Ekoln, Sweden

We quantified cover, population densities, size distribution and biomass of zebra mussels along 7 transects in eutrophic Lake Ekoln (Sweden). We also analyzed the elemental (C, N, P) composition of zebra mussel soft tissue and computed their retention rates of N and P their quantitative role in the lake’s nutrient budget. We hypothesized that zebra mussels play an important role in the nutrient budget of the lake and speculate that the successive harvesting of cultured mussels could contribute to the lake’s rate of recovery from cultural eutrophication. At depths exceeding 5 m, mussels covered consistently less than 5% or were absent. Similarly, mean densities were 3,158 ± 2,143 ind m−2 between 2 and 4 m, but rapidly declined at larger depths. Calculated clearance rates averaged 19.4 ± 2.3 km3 y−1, implying the entire lake is filtered every 8–10 days. Concentrations of N and P in mussel soft tissue averaged 100.9 ± 1.5 mg N g−1 DW and 9.3 ± 0.2 mg P g−1 DW. The lake population was estimated to 22.2 ± 2.6 × 1010 mussels, corresponding to a standing stock biomass of 362 ± 42 ton DW, or conservative estimates of 36.6 ± 4.3 ton N and 3.4 ± 0.4 ton P. Assuming a life span of 2–3 years gives a retention estimate of 1.2–1.8 ton P y−1 by mussels, corresponding to 50–77% of the annual P influx from Uppsala sewage treatment plant to the lake. Similarly, annual N-retention by zebra mussels makes up 13–20 ton N y−1, largely equaling the annual N-deposition from atmospheric sources on the lake’s surface. These retention rates correspond to only a few percent of the annual P-load from agricultural sources, but we argue that the quantitative role of zebra mussels in nutrient budgets is much larger if these budgets are adjusted for the bias introduced by coarse estimates of N and P pools that include a large share of refractory P.

Trace metal concentrations in Mediterranean blue mussel and surface sediments and evaluation of the mussels quality and possible risks of high human consumption

The concentrations of trace metals (Fe, Zn, Mn, Ni, Cu, Co and Cr) were determined for the first time in Mediterranean blue mussels (Mytilus galloprovincialis) and surface sediments. The mussel and sediment samples were collected from five sites on the Montenegrin coastal area (southeastern Adriatic Sea) in the fall of 2005 and 2006. The collected samples were digested with a microwave digestion system. The maximum Fe, Zn, Mn, Ni, Cu, Co and Cr mean concentrations in the mussel samples were 603.0, 345.0, 85.0, 18.9, 17.2, 9.1 and 4.2mg/kg of sample dry weight, respectively. The maximum Fe, Mn, Cr, Ni, Zn, Cu and Co concentrations in the sediment samples were 40867, 943.0, 382.0, 336.0, 67.2, 24.8 and 16.9mg/kg of sample dry weight, respectively. A correlation between the metal levels found in the mussel soft tissues with those found in sediments, for both 2005 and 2006, could be established, except for the levels of Zn observed.

Biochemical responses of Mytilus galloprovincialis as biomarkers of acute environmental pollution caused by the Don Pedro oil spill (Eivissa Island, Spain)

In the present work, the potential use of several antioxidant and detoxification biomarkers in the digestive gland of wild mussels ( Mytilus galloprovincialis) for biomonitoring the marine pollution induced by the Don Pedro oil spill has been investigated. Two locations from the East to South-East of Eivissa (Ibiza) and Formentera islands were selected, one extensively affected by the oil spill and the other one not affected and considered as the control area. Mussels were sampled one, two and six months after the Don Pedro accident. Polycyclic aromatic hydrocarbon (PAH) levels were significantly increased in the soft tissues of mussels in the affected area one month after the disaster, returning to normal values after six months. Markers of oxidative damage in lipids – malondialdehyde, and in proteins – carbonyl derivates, and antioxidant enzyme – catalase, superoxide dismutase and glutathione peroxidase, activities significantly increased as result of the spill oil after one month, returning to basal values at two month sampling time. Glutathione/glutathione disulfide ratio (GSH/GSSG), as a marker of the redox status, was reduced after one and two months indicating a more oxidized situation. Markers of detoxification – glutathione- S-transferase and cytochrome P4501A activities and metallothionein gene expression – were significantly increased by the oil spill one month after the accident, returning to the basal values at two month sampling time. In conclusion, the Don Pedro accident induced a transient situation of PAHs pollution resulting in enhanced antioxidant and detoxification defense systems in the wild mussel M. galloprovincialis returning to normal levels six months from the spill. The selected biomarkers are a useful tool for biomonitoring the response to acute exposure to pollutants in marine mussels.

Comparison of the 2000 and 2005 spatial distributions of heavy metals in wild mussels from the North-Atlantic Spanish coast

Spatial distributions of Cd, Cu, Hg, Pb and Zn in Mytilus galloprovincialis in 41 sampling sites in the North-Atlantic Spanish coast were monitored in 2000 and 2005 to assess the coastal environmental pollution. A pool of mussel soft tissue was prepared using 50 or more individuals representing the available size range. Samples were grounded, homogenised and quantified by atomic absorption spectrometry. Quality of the chemical analyses was assessed by participation in periodic interlaboratory exercises. Univariate and multivariate statistical studies, Principal Components Analysis and Procrustes rotation (a technique intended to compare several data spaces) were carried out. Some decreasing trends were observed for the concentrations throughout the 2000–2005 period, mainly for Hg and Pb. In general, the Northern area showed higher median concentrations (e.g., 3.79 and 4.28mg Pb/kg dry weight, and 0.160 and 0.191mg Hg/kg dry weight, for 2000 and 2005, respectively) than the Atlantic ones (e.g., 1.47 and 1.44mg Pb/kg dry weight, and 0.097 and 0.084mgHg/kg dry weight, for 2000 and 2005, respectively). Nevertheless, some Atlantic sampling points, located far from human inputs (cities, industries, rivers, etc.) exhibited high concentrations of Cd, which was attributed to the influence of the natural upwelling processes which occur annually in that geographical region.

Monitoring of heavy metals in wild mussels ( Mytilus galloprovincialis) from the Spanish North-Atlantic coast

Concentrations of five heavy metals (Hg, Cd, Pb, Cu and Zn) were determined in tissues of wild mussels ( Mytilus galloprovincialis) collected at 41 stations located on the Spanish Atlantic and Northern coasts to assess the levels and spatial distribution of metals in the environment. This study, performed in 2005, constituted a contribution to the last international OSPAR pollution monitoring survey. A pool of mussel soft tissue was prepared using 50 or more individuals, representing the size range present at the sampling points. Quantification was carried out after a nitric acid digestion by atomic absorption spectrometry, AAS (Cd and Pb by electrothermal AAS; Cu and Zn by flame AAS; and total mercury by the cold vapour technique). The quality of the chemical analyses was assessed by interlaboratory exercises carried out on a regular basis. In general, the levels of the metals were higher for the Northern region than for the Atlantic one (except for a sampling site close to Vigo, one of the main Galician industrial areas). Some Galician sampling points (Atlantic coast, NW of Spain) located far from human inputs showed high Cd concentrations, which were attributed to the annual upwelling processes in this region. The levels of Cu increased from Northwest to East, whereas Zn concentrations were very homogeneous throughout the two studied geographical regions. These results were confirmed using multivariate studies (PCA and cluster analysis), as well as international ‘background assessment concentrations’ criteria.

What a difference a species makes: a meta–analysis of dreissenid mussel impacts on freshwater ecosystems

We performed a meta‐analysis of published studies and long‐term monitoring data sets to evaluate the effects of dreissenid mussels (Dreissena polymorpha and D. rostriformis bugensis), two of the world's most problematic biological invaders, on the biogeochemistry, flora, and fauna of lakes and rivers across North America and Eurasia. Dreissenid effects were structured along two distinct energy pathways. For the pelagic–profundal pathway, large mean reductions in phytoplankton (−35% to −78%) and zooplankton (−40% to −77%) biomass occurred and were dependent on habitat type. The largest effects were found in rivers, followed by littoral and pelagic habitats in lakes. In contrast, benthic energy pathways within littoral habitats of lakes and rivers showed dramatic increases in mean benthic algal and macrophyte biomass (+170% to +180%), sediment‐associated bacteria (about +2000%), non‐dreissenid zoobenthic biomass (+160% to +210%), and total zoobenthic biomass, which includes dreissenid mussel soft tissues (+2000%). Our study quantifies the remarkable ability of these invasive mussels to shift aquatic food webs and energy flow from pelagic–profundal to benthic–littoral energy pathways, and it provides a basis for forecasting their impacts in diverse freshwater ecosystems. Our meta‐analysis approach was a powerful tool for moving beyond the idiosyncrasies of individual case studies and may be equally powerful for assessing impacts of other biological invaders.

Trace Metal Content in Mussels, Perna viridis L., Obtained from Selected Seafood Markets in a Metropolitan City

Mussels, Perna viridis L., obtained from three selected seafood markets in Metro Manila, were tested for metal content including cadmium, copper, lead, and zinc through atomic absorption spectrophotometry. Water samples from Bacoor Bay, Cavite, which supplies mussels to the market, were likewise subjected to similar metal analyses. Of the metals analyzed in the soft tissues of mussels, only copper and lead with highest obtained values of 10.4 mg/kg and 2.3 mg/kg, respectively exceeded the PEMSEA guideline for safe human consumption. Water samples collected from the harvest sites in Bacoor Bay showed high concentrations of cadmium (0.023 mg/L) and lead (0.25 mg/L) that exceeded the standards of DENR, ASEAN, and US EPA. Zinc, though detected in relatively high concentrations in both water (0.03 mg/L) and soft tissues (12.16-14.43 mg/kg) of mussels remained below the criteria set by the above-mentioned agencies. Overall, the present study indicates that mussels being sold in selected Metro Manila seafood markets were contaminated with metals, notably Cu and Pb, at concentrations that are unsafe for human consumption and thus, represents a health risk.

The effects of lead bioaccumulation on filtration rate of zebra mussel (Dreissena polymorpha) from Anzali wetland–Caspian Sea

In this study, the effects of lead on filtration rate of zebra mussel (Dreissena polymorpha) together with the accumulation of lead in the soft tissue of the mussels, were investigated. Studies showed different effects of lead in all concentrations. In three concentrations of lead (2, 48, and 93 µg L−1), no significant differences were investigated between filtration rates of mussels in treatments and also between treatments and control (respectively 102, 93, and 84% of control). Whilst, at concentration 455 µg L−1 the filtration rate of mussels decreased to 40% compared to control. In this study mussels in different lead treatments had the same exposure time, length range, and temperature. Therefore, in this experiment accumulation of lead in the soft tissue of the mussels is affected by the differences at lead concentration in treatments. Initial concentration of lead has a direct effect on its accumulation in the tissue of the mussels. In the highest concentration of lead, the most accumulation of lead in the soft tissue of mussels was observed and in the lowest concentration of lead, the least accumulation of lead in the soft tissue of mussels was found.

Purification and characterisation of ferritin from the Baltic blue mussel Mytilus trossulus

Baltic blue mussels Mytilus trossulus were collected from the Gulf of Gdansk (southern Baltic Sea) in order to isolate ferritin from its soft tissues, as well as to purify and characterise this protein. Proteins were isolated from the inner organs of M. trossulus (hepatopancreas, gills and soft tissue residue) by thermal denaturation (70◦C) and acidification (pH 4.5) of the homogenates, followed by ammonium sulphate ((NH4)2SO4) fractionation. The ferritin was then separated by ultracentrifugation (100 000× g, 120 min.). The protein content in the purified homogenates was determined by the Lowry method using bovine serum albumin (BSA) and horse spleen ferritin (HSF) as standards. PAGE-SDS and Western blotting analysis permitted identification of ferritin in the purified preparations. Additionally, the purified homogenates and mussel soft tissue were analysed for their heavy metal contents (especially cadmium and iron) in a Video 11 E atomic absorption spectrophotometer, following wet digestion of the samples (HNO3/HClO4). * This work was supported financially by the Committee for Scientific Research, grant No. 3/P04E/035/22, and the Institute of Oceanology statutory research grant. The complete text of the paper is available at http://www.iopan.gda.pl/oceanologia/ 526 J. Potrykus, A. Kosakowska The electrophoregrams showed that the inner organs of M. trossulus contained ferritin, which, like plant ferritin, is characterised by the presence of subunits in the electrophoregram in the 26.6–28.0 kDa range. The highest ferritin content was recorded in the hepatopancreas, followed by the gills and the soft tissue residue. With regard to the sampling stations, the highest content of ferritin was noted in the animals sampled off Sopot (station D3), and in those collected by a diver off Jastarnia (W1) and Gdynia (W4). Ferritin isolated from the inner organs of mussels collected from these stations also contained the largest quantities of heavy metals (Cd and Fe). Ferritin isolated from the inner organs of mussels collected by a diver from wrecks – sites where the concentrations of iron and other trace metals in the sea water are high – contained higher quantities of heavy metals (Cd and Fe) than the ferritin isolated from the inner organs of mussels collected with the drag. This confirms that ferritin is a protein able to store and transport not only iron, but also, though to a lesser extent, some other heavy metals, including cadmium.

Comparison between the mercury contamination in populations of Unio pictorum mancus (Mollusca, Bivalvia) from two lakes of different trophic state: the oligo-mesotrophic Lake Maggiore and the eutrophic Lake Candia

This research was designed to evaluate the influence of mussel (Unio pictorum mancus) size on mercury concentration in mussel soft tissues. It also evaluated the relationships between calcium, mercury and selenium in the mussel tissues. The mussel populations from the deep, meso-oligotrophic Lake Maggiore and the shallow, eutrophic Lake Candia were analyzed. The mean concentration of mercury in the tissues was 0.075 mg kg-1 in Lake Maggiore mussels and 0.033 mg kg-1 in Lake Candia mussels. The local mercury content in the mussel biomass per surface unit was about eleven-fold higher in Lake Maggiore (5.99 μg Hg m-2) than in Lake Candia (0.55 μg Hg m-2). This wide difference was due firstly to the larger population density (46.86 vs 6.93 ind m-2) and secondly to the higher individual content (0.128 vs 0.079 μg Hg ind-1) in Lake Maggiore than in Lake Candia. These differences in population density and individual mercury content are the result of both biological and environmental characteristics. Lake trophy and water renewal affect population density and individual growth rate, and ultimately determine their impact on biogeochemical cycles by regulating the mussel standing stock. The relationships between mercury, calcium and selenium were taken into account.

Inducibility of metallothionein biosynthesis in the whole soft tissue of zebra mussels Dreissena polymorpha exposed to cadmium, copper, and pentachlorophenol

Freshwater mussels Dreissena polymorpha (Pallas, 1771) were exposed to the elevated concentrations of Cd (10, 50, 100, and 500 microg/L), Cu (10, 30, 50, and 80 microg/L), and an organochlorinated pesticide, pentachlorophenol (PCP) (1, 10, and 100 microg/L). Induced synthesis of biomarker metallothionein (MT) and changes in concentrations of cytosolic Cd, Cu, and Zn in the whole soft tissue of mussels were monitored after a 7-day laboratory exposure to the contaminants. A clear dose-dependent elevation in the MT concentration was observed after exposure to Cd at doses of 10-100 microg/L, and this increase of MT content was accompanied with a linear increase of cytosolic Cd. Cd concentration of 500 microg/L caused no additional increase of MT and Cd in mussel cytosol, suggesting possible toxic effects due to exceeding cellular inducible/defense capacity. Cu exposure resulted with variable changes in MT concentrations, with no clear linear relationship between MT and Cu concentrations in water, although a progressive dose-dependent accumulation of Cu in the soluble fraction of mussel tissues was recorded. A decrease of cytosolic Zn was evident at higher exposure concentrations of both metals used. PCP in concentrations applied was unable to induce MT synthesis, but the higher concentrations of PCP influenced the cytosolic metal concentrations. In conclusion, the results obtained confirm the specificity of MT induction in D. polymorpha as an biological response on metal stimulation, especially by cadmium, being more closely correlated to MT than copper within the ecologically relevant concentration range. The strong induction potential of cadmium as well as an absence of MT induction following exposure to PCP as an organic chemical contaminant are supporting evidences for usage of zebra mussel MT as a specific biomarker of Cd exposure in biomonitoring programs.