Organs Of Mussels Research Articles

Ocean acidification impact on the uptake of trace elements by mussels and their biochemical effects

This study delves into the intricate interplay between ocean acidification (OA), metal bioaccumulation, and cellular responses using mussels (Mytilus galloprovincialis) as bioindicators. For this purpose, environmentally realistic concentrations of isotopically labelled metals (Cd, Cu, Ag, Ce) were added to investigate whether the OA increase would modify metal bioaccumulation and induce adverse effects at the cellular level. The study reveals that while certain elements like Cd and Ag might remain unaffected by OA, the bioavailability of Cu and Ce could potentially escalate, leading to amplified accumulation in marine organisms. The present findings highlight a significant rise in Ce concentrations within different mussel organs under elevated pCO2 conditions, accompanied by an increased isotopic fractionation of Ce (140/142Ce), suggesting a heightened potential for metal accumulation under OA. The results suggested that OA influenced metal accumulation in the gills of mussels. Conversely, metal accumulation in the digestive gland was unaffected by OA. The exposure to both trace metals and OA affects the biochemical responses of M. galloprovincialis, leading to increased metabolic capacity, changes in energy reserves, and alterations in oxidative stress markers, but the specific effects on other biomarkers (e.g., lipid peroxidation, some enzymatic responses or acetylcholinesterase activity) were not uniform, suggesting complex interactions between the stressors and the biochemical pathways in the mussels.

Distribution and polymorphism of enzymes involved in antioxidant protection and xenobiotics biotransformation in the mediterranean mussel Mytilus galloprovincialis

The aim of the work was to determine the tissue distribution, activity and polymorphism of 13 enzymes involved in antioxidative protection and xenobiotics biotransformation in a five bivalve mussel organs (hepatopancreas, ctenidia, mantle, leg, adductor muscles). Iso-allozyme analysis was performed by electrophoresis, correlation relationships between the studied enzymes in the whole mussel body were carried out using Spearman’s correlation analysis. It was found that all studied enzymes are polymorphic, each organ differed in the level of enzyme activity and a set of multiple forms. The coordinated functioning of protective enzymes in various mussel organs was demonstrated. Keywords: antioxidant enzymes, coordination of protective enzymes, enzymes of biotransformation, iso-allozyme analysis, Mytilus galloprovincialis

Histological Alteration of Green Mussel Perna viridis Organs Exposed to Microplastics

Microplastic in the oceans might interfere the health of marine organisms, including the green mussels (Perna viridis). This is due to microplastic accumulation in mussels organs, such as gills, hepatopancreas, and gonads. Therefore, tissue alteration is a good indicator for ecological risk analysis and other ecotoxicological study activities. Green mussels with shells 4.1 to 5.0 cm in length were collected from Mandalle waters, Pangkep Regency (Pangkajene Islands), Indonesia. Green mussels were exposed for seven days to microplastic with concentrations of 0.05 (A), 0.5 (B), and 5 (C) g/L. The results showed that the higher the concentration of microplastics exposed to the green mussel, the higher the accumulation of microplastics in the body of the mussel, within the tested concentrations. The increased concentration of microplastics increased the level of tissue alteration in the gills, hepatopancreas, and gonads, with the most sensitive organ being the hepatopancreas. Overall, the study confirmed that the histological assay of mussel organs could be used as a biomarker in ecotoxicological studies.

Seasonal distribution of cadmium, lead, nickel, and magnesium in several tissues of mussels from the Algerian coasts.

This study aims to investigate the distribution of heavy metals (Cd, Pb, Ni, and Mn) in different organs of two marine mussel species, Perna perna collected from Figuier site and Mytilus galloprovincialis sampled from Sercouf and Algiers port sites of the Algerian coast. Thirty individuals (>5cm length) were seasonally sampled over a 1-year period from each site, and condition index (CI) and gonado somatic index (GSI) of mussels were calculated. The gill, digestive gland, rest of soft tissues, and gonad were accurately isolated and heavy metal contents were analyzed by ICP-MS. Heavy metal results, expressed on μg/g dry weight, ranged from 0.1 to 2.6 Cd, 0.1 to 17.15 Pb, 0.36 to 25.7 Ni, and 3.68 to 74.76 Mn. Thus, typical distribution of studied metals in various organs of mussels was found. In fact, the digestive gland followed by gill revealed significantly high metal concentrations. However, gonad showed low heavy metal contents. Different patterns of heavy metal distribution in various organs of mussels were found at the three sampling sites. High levels of Cd, Pb, Ni, and Mn were detected in mussels of Sercouf, Algiers port, and Figuier sites, respectively. According to the Algerian and European norms, mussels collected from all sites were healthy except those of Algiers port sampled in autumn and winter seasons where lead contamination was found.

A dynamic model of cadmium bioaccumulation in Lamellidens marginalis, an edible shellfish in India

Mussels, as food is widely accepted by people around the world as it possesses good nutritive value. Along with the local fishes, a gradual increase in the market demand of the Lamellidens marginalis is observed in the eastern part of India. These mussels are collected from reservoirs by the local people for their daily requirements and usual business. The reservoirs receive the wastewater or sewage from the nearby tanneries and households. Consequently, people are prone to a high risk of cadmium pollution through the consumption of mussels. Thus, the study of the bioaccumulation of cadmium in the organs of mussel is felt be need of the hour.A dynamic model was constructed to observe the daily accumulation of cadmium in the different organs of mussel. The model was constructed in the STELLA 6.0 software, and a sensitivity analysis was performed followed by calibration and validation.The scenario analysis revealed that the bioaccumulation of cadmium in the gills was sensitive to the input rate of cadmium to the system. The retention of cadmium in the alimentary canal and the kidney was dependent on the excretion rate of mussels. Cadmium deposition in the muscles and hepatopancreas was strongly regulated by the transfer rate of cadmium from the alimentary canal and the depuration rate respectively. However, the cadmium bioaccumulation in the foot was dependent on the surface area of foot. The sensitivity analysis showed that the input rate of cadmium into the system was the system sensitive parameter. If the cadmium is checked at the entry point of the reservoir, then the mussels could be easily harvested by the local people, and there would be less risk of cadmium pollution to the human.

Adherence of microplastics to soft tissue of mussels: A novel way to uptake microplastics beyond ingestion

Microplastic pollution is recognized as an emerging threat to aquatic ecosystems. One of the main environmental risks associated with microplastics is their bioavailability to marine organisms. Up to date, ingestion has been widely accepted as the sole way for the animals to uptake microplastics. Nevertheless, microplastics have also been found in some organs which are not involved in the process of ingestion. We hypothesize that the animal might uptake microplastics through adherence in addition to ingestion. To test this hypothesis, we collected mussels from the fishery farms, conducted exposure/clearance experiments and analyzed the accumulation of microplastics in specific organ of mussels. Our studies clearly showed the uptake of microplastic in multiple organs of mussels. In the field investigations, we found that the abundance of microplastic by weight but not by individual showed significant difference among organs, and the intestine contained the highest level of microplastics (9.2items/g). In the uptake and clearance experiment, the accumulation and retention of microfibers could also be observed in all tested organs of mussels including foot and mantle. Our results strongly suggest that adherence rather than ingestion led to the accumulation of microplastics in those organs which are not involved in ingestion process. To our best knowledge, it is the first time to propose that adherence is a novel way for animals to uptake microplastics beyond ingestion. This new finding makes us rethink about the bioavailability, accumulation and toxicity of microplastics to aquatic animals.

Examining the physiological plasticity of particle capture by the blue mussel, Mytilus edulis (L.): Confounding factors and potential artifacts with studies utilizing natural seston

Historically, particle capture efficiency (CE) in suspension-feeding bivalve molluscs has been shown to be strongly dependent on particle size, increasing asymptotically to a maximum of about 100% for particles ca. ≥ 4 μm in diameter. Recent advances in the analysis of the particulate matter of seston have allowed for more precise studies of bivalve feeding under natural conditions. Some studies have reported that the mechanisms associated with particle capture exhibit physiological plasticity, and under certain conditions smaller cells and particles are captured in preference to larger ones. For bivalves, however, there is no mechanistic explanation that would account for such fine-scale control of CE based on size. The current study experimentally assessed the seasonal control of CE by the blue mussel, Mytilus edulis, employing a flow-through system to examine particle capture of natural seston. The natural particle field was analyzed using two different types of particle analyzers, the LISST-100X and the Coulter Multisizer IIe. Mussels were simultaneously delivered synthetic microspheres of defined diameter (2–45 μm) to control for the effects of seasonal differences in the size and shape of natural particles. The capture of microspheres was quantified by means of flow cytometry (FCM), and results cross-checked with the Multisizer. Additionally, gene expression of a mucosal lectin (MeML) associated with the feeding organs of mussels was examined as a biomarker for physiological response to seasonal changes in the particle-food supply. Results demonstrated that for microspheres ≥ 4 μm CE of mussels was always near 100%, and did not change seasonally. In contrast, there was an apparent seasonal shift in CE of natural particles, with particles 17-to-35 μm in equivalent spherical diameter (ESD) occasionally being captured at lower efficiencies than particles 4-to-15 μm in ESD (e.g., during September and December). No relationship between MeML expression and seasonal CE was found. These findings call into question the physiological plasticity of CE in mussels and alternative hypotheses are presented. We suggest that the purported changes in CE are not a consequence of behavioral or physiological responses of mussels, but rather a result of one or more of the following confounding factors; 1) instrument artifacts that can arise as a result of the way in which laser and electronic particle counters calculate ESD to estimate particle size; 2) disaggregation of flocculent material collected from control chambers; 3) post-capture escape of highly motile phytoplankton cells from the infrabranchial camber; 4) qualitative factors of the particles that could affect capture; or 5) mathematical happenstance of calculating CE on particle-size classes that contain widely different numbers of particles.

Assessment of Toxoplasma gondii levels in zebra mussel (Dreissena polymorpha) by real-time PCR: an organotropism study.

Water quality is a public health concern that calls for relevant biomonitoring programs. Molecular tools such as polymerase chain reaction (PCR) are progressively becoming more sensitive and more specific than conventional techniques to detect pathogens in environmental samples such as water and organisms. The zebra mussel (Dreissena polymorpha) has already been demonstrated to accumulate and concentrate various human waterborne pathogens. In this study, first, a spiking experiment to evaluate detection levels of Toxoplasma gondii DNA in zebra mussel organs using real-time PCR was conducted. Overall, lower DNA levels in the hemolymph, digestive gland, and remaining tissues (gonad and foot) were detected compared to mantle, muscle, and gills. Second, an in vivo experiment with 1000 T. gondii oocysts per mussel and per day for 21 consecutive days, followed by 14days of depuration time in protozoa-free water was performed. T. gondii DNA was detected in all organs, but greatest concentrations were observed in hemolymph and mantle tissues compared to the others organs at the end of the depuration period. These results suggest that (i) the zebra mussel is a potential new tool for measuring T. gondii concentrations and (ii) real-time PCR is a suitable method for pathogen detection in complex matrices such as tissues.

Lysosomal deoxyribonuclease II from the mussel Mytilus galloprovincialis: Characterization and seasonal activity

In view of the importance of Mytilus species in marine ecology and environmental quality assessment, all aspects of mussel enzymes that are related to environmental factors are of great relevance. A lysosomal enzyme, deoxyribonuclease II, a member of the acid deoxyribonucleases, has a major role in cellular DNA degradation. The presence and seasonal variations of the acid deoxyribonuclease (DNase) activity in the digestive gland and gills of the mussel Mytilus galloprovincialis were investigated. The enzyme was localized in the lysosomal vacuolar system of both gill and digestive gland tissues. Two active acid DNase isoforms were detected in the digestive gland (48 and 37 kDa) and one in the gills (48 kDa). All active enzyme isoforms coincided with protein bands immunoreactive to antibodies raised against human DNase II. Post-translational lysosomal processing of acid DNase in the digestive gland but not in the gills indicated tissue-specific enzyme maturation. The activity of acid DNase determined across the annual cycle showed a tissue-specific pattern that could be related to the seasonal activity of mussel organs and their biological function. In the digestive gland, high DNase activity was observed in relation to food availability and spawning. Higher enzyme activity in the gills observed in the autumn/winter period could be associated with feeding and cellular adaptation to low seawater temperatures.

Availability and utilization of waste fish feed by mussels Mytilus edulis in a commercial integrated multi-trophic aquaculture (IMTA) system: A multi-indicator assessment approach

Fish feed waste enhancement of the particulate food supply and performance of mussels Mytilus edulis suspended near salmon cages at an integrated multi-trophic aquaculture (IMTA) site was assessed using a multi-indicator approach. Dietary indicators included bulk measurements of seston quantity and nutritional quality, proximate analysis (PA), fatty acid (FA) and stable isotope (SI) composition. Mussel tissue indicators consisted of PA and FA composition. Mussel performance was assessed from physiological integrations (scope for growth, SFG), growth efficiency (K2) and condition index (CI). All measurements were made over 2 days at a commercial IMTA farm and a monoculture mussel farm in the Bay of Fundy (Canada). Significant differences detected in seston quantity and quality were within the range of natural spatial variability. The SFG of IMTA mussels was lower (28.71Jh−1) than monoculture mussels (38.71Jh−1) and reflected site differences in natural food availability and composition that affected absorption rate. PA of mussel organs didn't reflect a significant fish feed contribution to the mussel diet. However, dietary enhancement and assimilation of fish feed waste was demonstrated by significantly higher levels of feed FA biomarkers 20:1ω9, 18:2ω6, 18:1ω9 and low ω3/ω6 ratio in seston, mussel tissues and feces at the IMTA site than at the mussel farm. SI (δ13C and δ15N) in seston and mussel feces significantly differed among sites and IMTA mussels had significantly higher CI (21%) than monoculture individuals (16%). It was concluded that bulk indicators of the diet, short-term physiological integrations, and PA of mussel tissues have a limited capacity to detect dietary enhancement at IMTA sites. FA and SI tracers of fish feed waste were shown to be more sensitive for detecting the low-levels of diet enhancement within the large range of natural seston variation.

Energy status and immune system alterations in Elliptio complanata after ingestion of cyanobacteria Anabaena flos-aquae

Cyanobacteria have often been described as nutritionally poor for herbivorous organisms. To gain additional information on the potential impacts of invertebrates feeding on cyanobacteria, we fed Elliptio complanata mussels with two types of algae: Anabaena flos-aquae (cyanobacteria) and Pseudokirchneriella subcapitata (green algae). Physiological parameters were examined at the energy status, immune system and oxidative stress levels. Energy status was examined by following the rate of electron transport activity in mitochondria (a measure of cellular energy expense) and lipid/sugar stores in the visceral mass. The cyanobacteria were not actively producing toxins. Based on the digestive gland index, the mussels fed equally on either regime. However, the energy status in mussels fed A. flos-aquae revealed that the total sugar was lower in the digestive gland, whereas mitochondrial electron transport activity (MET), once corrected against the digestive gland somatic index, showed increased energy expenses. Acetylcholinesterase activity and lipid peroxidation (LPO) were also higher in mussels fed with A. flos-aquae compared with mussels fed with P. subcapitata. LPO was correlated by mitochondrial activity in both the digestive gland and gills, suggesting that oxidative stress resulted from metabolic respiration. Immunocompetence (phagocytic activity, natural killer cell-like activity, haemocyte count and viability) and humoral level of lysozyme were not affected in mussels by the algae or cyanobacteria regime. Moreover, the xenobiotic conjugating enzyme, glutathione S-transferase, hemoprotein oxidase and vitellogenin-like proteins were not affected in mussel organs via ingestion of A. flos-aquae. Our study suggests that ingestion of cyanobacteria leads to increased energy expenses, oxidative stress and increased acetylcholine turnover in mussels.

Assessment of the adaptation capabilities of the bivalves Modiolus modiolus (Linnaeus, 1758) and Crenomytilus grayanus (Dunker, 1853) under increased levels of heavy metals in the environment

The active biomonitoring method was used to examine the changes in heavy-metal (Fe, Zn, Cu, Cd, Mn, Pb, and Ni) contents in the organs (muscle, gonads, mantle, gills, digestive gland, and kidney) of the mussels Crenomytilus grayanus and Modiolus modiolus. The dynamics of trace element concentrations in mussel organs during the experiment were compared with their subcellular distribution. The defense strategy of M. modiolus consisted of the threshold accumulation of toxic metals in all organs followed by their excretion, whereas the strategy of C. grayanus involved short-term isolation from adverse environmental influence. Under chronic pollution, in C. grayanus the main loads occurred in the digestive gland and kidney. Under acute changes in environmental conditions, the processes of regulation (detoxification/excretion) of Fe, Mn, and Pb in this species were impaired substantially.

Correlation between the activity of intracellular Ca2+-dependent proteinase and the content of membrane lipid components in mussel, Mytilus edulis, upon accumulation of heavy metals

Correlation of calpain activity level and some membrane lipid component contents in organs of mussels, Mytilus edulis L., was shown in aquarial experiment on the study of mussel response reactions on the exposure of different levels of copper and cadmium. The correlation observed possibly could be explained by the effector role of membrane lipid components (arachidonic acid, phosphatidylinositol) on Ca(2+)-channels. Thus, the correlation between tissue lipid composition and protein functional activity was demonstrated with intracellular Ca2+ level as a key member.

Uptake, distribution, and bioaccumulation of copper in the freshwater mussel Anodonta anatina

Copper (Cu) is present in aquatic ecosystems in dissolved form, associated with suspended food particles, and as insoluble sulfide in the sediment. Due to its wide technical use and its presence in municipal and industrial waste waters, levels in rivers and sediments may be elevated. The aims of this study are to assess the relative importance of copper uptake by a typical freshwater mussel (Anodonta anatina), its distribution, accumulation among the mussel organs, and elimination. Using the stable isotope 63Cu as tracer, the mussels are exposed via the water (0.3 µmol L−1 Cu) or via the food (1.5 mg L−1 Cu-loaded algae, equivalent to 0.06 µmol L−1 Cu) for 24 days. The levels of exogenous and total Cu increase in all body compartments. Relative increases are highest in the digestive gland, followed by mantle and gills. Upon depuration for 12 days, 63Cu is quickly but not completely eliminated.

Relationship between metal levels in the vent mussel Bathymodiolus azoricus and local microhabitat chemical characteristics of Eiffel Tower (Lucky Strike)

The turbulent mixing of hydrothermal hot fluid with cold seawater creates large chemical gradients at a small spatial scale that may induce variable physiological and biochemical adaptations within the vent fauna. The adaptation to such a variable environment by the vent mussel Bathymodiolus azoricus relies on a dual symbiosis hosted in the gills, and digestion of particulate organic matter. The surrounding environment not only provides the necessary energy sources and suspended organic particles for the vent mussel nutrition, but also potentially toxic compounds such as metals. Our main goal was to see if there is a relation between metal accumulation in mussel organs and the chemical characteristics of their close environment. Mussels were collected at six locations in a cold part of the Eiffel Tower fluid-seawater mixing zone, characterized by distinct chemical compositions. Metals (Cd, Cu, Fe and Zn) and metallothioneins were quantified in the gills and digestive gland. The physiological condition of the sampled mussels was also evaluated using tissues and gill indices. Our study indicates that the accumulation of metals in B. azoricus is related to their spatial distribution and linked to fine scale environmental conditions that influence the physiological status of the organism.

The use of cholinergic biomarker, cholinesterase activity of blue mussel Mytilus edulis to detect the effects of organophosphorous pesticides

The aim of the study was to investigate the effects of organophosphorous pesticide on thecholinesterase activity of different organs of Mytilus edulis. The mussels were exposed to serial dilutions of the pesticides (0, 50, 100, 200, 500, and 1000 µg/l) for 96 h. A significant inhibition of the cholinesterase activity from gill occurred at the lowest concentration, which indicated that gill was the most sensitive organ. The moderate sensitive organs were foot and mantle, which wereinhibited by trichlorfon at 200 μg/l. The least sensitive organs were hemolymph, posterior adductor muscle and digestive gland were inhibited at 1000 μg/l. After incubation of the trichlorfon-exposed mussels for seven days in clean media, the cholinesterase activities from different organs of mussels were not cured completely. The cholinesterase activities from hemolymph, gill, posterior adductor muscle and digestive gland recovered, while the persistent inhibition of cholinesterase activity from foot and mantle were observed. Key words: Biomarker, cholinesterase, mussel, trichlorfon.

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.

Dynamics of glutathione- S-transferases in Mytilus galloprovincialis exposed to toxic Microcystis aeruginosa cells, extracts and pure toxins

Molluscs and especially bivalves are able to accumulate dinoflagelates, diatoms and cyanobacteria toxins, and, being vectors for these toxins, transfer them along food chains. The data obtained from laboratory experiments showed that bivalve molluscs are resistant to cyanobacteria toxins. In this work, we wanted to test if Mytilus galloprovincialis organs react to microcystins and other cyanobacteria compounds by inducing or decreasing its GST activity. Acclimated mussels M. galloprovincialis were exposed to the toxic Microcystis aeruginosa M13 strain. Exposure of mussels to toxins was done in three ways: living Microcystis cells, crude Microcystis extracts and pure toxins. The measurement of soluble and microsomal GST activity in the different mussel organs was done by using the substrates 1-chloro-2,4-dinitrobenzene (CDNB) and 2,4-dichloro-1-nitrobenzene (DCNB). Analysis of the GST activity of the control mussels using CDNB as a substrate showed that cytosolic activity is much more significant than microsomal. Intact M. aeruginosa cells did not induce any significant response from the mussels, showing that these animals are quite resistant to the cyanobacteria if they are intact. On the other hand, cell extracts caused an important effect in the gut, in the gills and in the labial palps, although in different ways. There was an increase in GST activity in the gut and gills of mussels exposed to Microcystis extracts, showing a response of this detoxication pathway, but in the labial palps a severe reduction in GST activity occurred. Pure MC LR+YR induced an increase in GST activity in all organs but the labial palps. The results showed that other substances apart from microcystins may cause stress to mussels and affect detoxication enzymes such as GST.

Heavy Metal Concentrations in Water, Sediment, Fish and Some Benthic Organisms from Tigris River, Turkey

In this study concentrations of heavy metals, such as Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn were determined in water, sediment, muscle, liver and gill of fish (Silurus triostegus, Mastacembelus simack, Mystus halepensis, Orthrias euphraticus) the muscle and liver of crab (Potamon fluviatilis), the internal organs of fresh water snail (Physa acuta), and mussel (Unio elongatulus), and in whole biomass of green algae (Spirogyra sp.) examples collected seasonally from three selected sites (I, II, and III) of Tigris River and from a reference site on Resan Creek. In general, the average Cd, Cu, Mn, Ni, Zn, and Fe values in Sites I, II, and III were found to be high in spring and summer. The concentrations of heavy metals in the Tigris River are compared with previous studies in the same sites. The results showed that Cu levels have gradually decreased during recent years. In Tigris River, among the living organisms, i.e., those which are living in benthic region and showing biomonitor characteristic, crab, snail, green algae, mussel and fish are seen to be formed in sequence. Cu, Fe, Mn and Zn values obtained from the muscle of fish and from the mass of internal organs of mussel and snail were found to be under the acceptable values suggested.

Comparative Analysis of Subcellular Distribution of Heavy Metals in Organs of the Bivalve Mollusks Crenomytilus grayanus and Modiolus modiolus in a Continuously Polluted Environment

The distribution of Zn, Fe, Ni, Cu, Mn, Cd, and Pb in subcellular fractions, and of Cd, Zn, and Cu in cytoplasm proteins of the kidney and digestive gland of the mussels Crenomytilus grayanus and Modiolus modiolus, sampled from contaminated and conditionally clean areas, was studied. It was found that, in a contaminated environment, the organs of mussels were more highly enriched with metals. It was shown that essential trace elements were accumulated mostly in the cytosol of organs of both molluscan species from contaminated areas, whereas in the background areas the trace elements were associated mostly with membrane structures in Gray's mussel, C. grayanus, and with the cytosol in M. modiolus, the northern horse mussel. The lead was bound mostly to membrane structures in organs of both mussel species at all stations. The method of gel chromatography enabled us to isolate metallothionein-like proteins from the kidney of the northern horse mussel sampled in contaminated areas, whereas their concentration in the kidney of Gray's mussels was lower than the limiting error of the method. It is supposed that in the kidney of Gray's mussel the synthesis of metallothionein-like proteins was quenched by the integrated effect of the accumulated metals.