Clam Ruditapes Decussatus Research Articles

Heterogeneity of macrozoobenthic assemblages within a Zostera noltii seagrass bed: diversity, abundance, biomass and structuring factors

The macrobenthic fauna community of a 70-km 2 Zostera noltii seagrass bed (Arcachon bay, France) was studied by sampling 49 stations systematically. A total of 126 taxa were identified. Cluster Analysis based on χ 2 distance showed that in this apparently homogeneous habitat, four distinct macrobenthic communities could be identified. Multiple Discriminant Analysis highlighted the major contribution of the overlying water mass as a forcing variable, and, to a lesser extent, of tidal level and Z. noltii's below-ground parts. Seven stations did not constitute any conspicuous group, and were characterized by a low biomass of leaf (<28 g DW m −2), considered as the lowest value to constitute a Z. noltii community. Less than 24% of the seagrass bed was situated in more oceanic waters and at a quite low tidal level. In this relatively stable environment, the macrofauna community was characterized by a high species richness (mean = 39) and a moderate density and high biomass (12 638 individuals m −2 and 25 g AFDW m −2, respectively). Annelids dominated, particularly the oligochaetes. When physical constraints increased (emersion or brackish water conditions), diversity decreased, abundance and biomass increased. The seagrass bed (55%) was flooded with highly fluctuating waters in term of temperature and salinity, here species richness was low (mean = 27) but abundance and biomass were high (24 384 individuals m −2 and 28 g AFDW m −2, respectively), with a dominance of molluscs. The meadow (7%) was in external waters but at a higher tidal level (2.4 m vs 1.8 m above medium low tide level). This community was characterized by the particularly high density (41 826 individuals m −2) and dominance of oligochaetes (79% of total abundance). Species richness was high (mean = 37) here. A fourth community, extending over 12% of the meadow was dominated by the gastropod Hydrobia ulvae but could not be linked to a specific forcing variable. This study confirmed the almost complete replacement of the native clam Ruditapes decussatus by the Manila clam Ruditapes philippinarum since its introduction in the 1980s.

Effect of three xenobiotic compounds on Glutathione S-Transferase in the clam Ruditapes decussatus

The effects of 4,4′DDE, methoxychlor and imidazole were studied on glutathione S-transferase activities in the gills and hepatopancreas of the clam Ruditapes decussatus. The contamination doses were 0.14 μM for 4,4′DDE, 0.14 μM for methoxychlor and 25 μM for imidazole. GST activities were spectrophotometrically measured. SDS-PAGE and isoelectric focusing (IEF) were used to separate the different GST isoforms in control and treated animals, followed by Western blotting performed with anti-alpha, anti-mu and anti-pi GST anti-sera. In the hepatopancreas, GST-CDNB activities were always two to five-fold lower than in the gills where the activities were significantly increased after exposure to 4,4′DDE (ca. 1.6-fold) and to methoxychlor (ca. 1.3-fold) compared to the controls (ca. 3 μmol min −1 mg −1protein) whereas they remained unchanged after treatment with imidazole. When using glutathione S-transferase anti-alpha, anti-mu and anti-pi anti-sera, a single 26 kDa polypeptide was observed in the hepatopancreas and in the gills in all the tested conditions. Five GST subunits were observed after IEF showing greater immuno-reactivity with the anti-pi mammalian class antiserum than with the anti-alpha or anti-mu mammalian anti-sera. One isoform of p I 5.77 was particularly induced by 4,4′DDE and methoxychlor; it was recognized by the three anti-sera tested and seemed to be more efficient in the gills than in the hepatopancreas. This isoform may play a role in organochlorine detoxication.

Molecular detection of a haplosporidian parasite in carpet shell clam Ruditapes decussatus from Spain

A protozoan parasite identified by histology as a haplosporidian was detected in carpet shell clam Ruditapes decussatus from Spain during routine samplings. Analysis based on the sequence of the small subunit ribosomal RNA gene revealed that this organism was related to the haplosporidian group, mainly to Urosporidium. A specific probe was used for in situ hybridization studies to show the specificity of the amplified sequence.

Preliminary study of the clam Ruditapes decussatus exposed in situ to metal contamination and originating from the Gulf of Gabès, Tunisia.

Preliminary study of the clam Ruditapes decussatus exposed in situ to metal contamination and originating from the Gulf of Gabès, Tunisia.

Does zinc produce reactive oxygen species in Ruditapes decussatus?

Zinc is an essential trace element with many enzymatic functions that include antioxidant properties. To investigate whether an excess of Zn in the cells produces cytotoxicity or tissue damage or an imbalance in the antioxidant systems, marine clams ( Ruditapes decussatus) were exposed to two sublethal Zn concentrations (100 and 1000 μg L −1) for 28 days. The effects of Zn on the activities of protective antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase, both total and selenium-dependent), lipid peroxidation, and metallothionein induction were followed in the gills and digestive gland of these clams. The results indicate that the effect of Zn exposure in this clam species depends not only on the tissue but also on the Zn concentration present. In the gills, catalase activity was enhanced by Zn exposure, whereas total glutathione peroxidase activity was inhibited. Lipid peroxidation occurred only in the clams exposed to the highest Zn concentration. In the digestive gland, the impact of Zn exposure on metabolic activity was less evident than in the gills. The most evident effect in both tissues was the enhancement of catalase activity by Zn exposure. Catalase and total glutathione peroxidase activities as well as lipid peroxidation are promising biomarkers to assess the effects of Zn in the gills of R. decussatus.

Energy balance, gonad development and biochemical composition in the clam Ruditapes decussatus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 258:133-145 (2003) - doi:10.3354/meps258133 Energy balance, gonad development and biochemical composition in the clam Ruditapes decussatus A. Pérez Camacho1,*, M. Delgado1, M. J. Fernández-Reiriz2, U. Labarta2 1Instituto Español de Oceanografía, Muelle de Ánimas s/n, 15001 La Coruña, Spain 2Consejo Superior Investigaciones Cientificas (CSIC), Instituto de Investigaciones Marinas, Eduardo Cabello 6, 36208 Vigo, Spain *Email: alejandro.perez@co.ieo.es ABSTRACT: This study evaluates the influence of different states of energy balance, positive and negative, on the accumulation and utilisation of energy reserves during the period of gonad development in the clam Ruditapes decussatus (L.). Our results show a clear sexual differentiation in the biochemical composition of the clams. The differences were associated with gonad development and were particularly evident in proteins and lipids. These findings imply that separation of the sexes for studying variations in the biochemical composition of sexually developed specimens is essential, and thus questions the results of previous studies in which both sexes were analysed simultaneously. Gonad development occurs under conditions of both positive and negative energy balance, and permits the development of a model of the utilisation of reserves during gonad development, which is closely linked to the clam¹s energy balance. Under conditions of positive energy balance, the amount of food ingested provides sufficient energy for both metabolic consumption and the accumulation of reserves. The absolute value of all biochemical components increases, in particular for lipids in the case of female clams, with no evidence of consumption of glycogen and other carbohydrates or their conversion into lipid reserves. Conditions of negative energy balance lead to a moderate degree of organic weight loss in the clams. Glycogen and other carbohydrates are rapidly consumed, falling to almost a quarter of initial values, whilst protein and lipid levels remain constant in females. Lipid values decrease slightly in males. Finally, under situations of extreme nutritive stress (when energy reserves are scarce) there is a loss of all biochemical components in a specific order of priority. Most of the glycogen and other carbohydrates are consumed initially (a decrease of 61 and 74%, respectively), followed to a lesser extent by lipids in males (40%) and then proteins (between 20 and 25%). In females, there was no lipid loss until the majority of the carbohydrates and part of the proteins had been consumed, indicating that lipids constitute the reproductive reserve par excellence in this species. KEY WORDS: Ruditapes decussatus · Energy balance · Gonad development · Biochemical composition Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 258. Online publication date: August 29, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Antioxidant enzyme activities, metallothioneins and lipid peroxidation as biomarkers in Ruditapes decussatus?

Antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPX)) were studied in the gills and digestive gland of clams Ruditapes decussatus from different sites of the Ria Formosa (south coast of Portugal) in order to validate these enzymes as biomarkers of metal exposure. Two other potential biomarkers, lipid peroxidation expressed as malondialdehyde (MDA), and metallothionein (MT) levels were also measured. This study demonstrates that mitochondrial and cytosolic SOD activity changed while CAT activity (cytosolic and mitochondrial) was higher in the gills of clams from the three sites affected by different sources of contamination. GPXs (total and Se-dependent) were inhibited in the gills of clams from sites A (directly influenced by sewage industrial wastes) and B (directly influenced by harbor facilities). MT and MDA levels were higher in the gills of clams from these two sites and in the digestive gland of clams from the third site (C, main navigation channel and exchange with Atlantic ocean). These results suggest that CAT and GPX activities and MDA levels especially in the gills of clams can be used as biomarkers for monitoring environmental pollution.

Variation of metal and metallothionein concentrations in a natural population of Ruditapes decussatus.

The spatial and seasonal variation of total and subcellular distribution of Cd, Cu, and Zn was followed in different tissues (gills, digestive gland, and remaining tissues) of the clam Ruditapes decussatus collected along a metal contamination gradient in the Ria Formosa lagoon (southern Portugal) and compared with metallothionein (MT) concentrations.Total metal concentrations decreased according to the sequence digestive gland > gills > remaining tissues for Cd, digestive gland approximately gills > remaining tissues for Cu and gills > digestive gland > remaining tissues for Zn. MT concentrations in these tissues decreased according to the same sequence observed for Cd. In all the tissues, the highest subcellular concentration was in the cytosol for Cd and Cu and in the pellet for Zn. Among the three metals, Cd concentrations showed the most evident spatial variation. In all tissues, total and subcellular Cd concentrations decreased from the inner parts of the lagoon toward the ocean. However, no significant spatial or seasonal variation occurred in clam tissues for the other two metals, though marginal elevated Cu concentrations were observed in the inner parts of the lagoon. Therefore, Cu subcellular distribution in clam tissues was not significantly altered by Cu changes in the lagoon and are the baseline levels for normal metabolism of this clam population. The fact that total Zn concentrations remained unchanged both spatial and seasonal suggested that these clams regulate Zn in their tissues. In the three tissues, MT bind most significantly to Cd and Cu, while Zn, although binding to MT, is preferably bound to other ligands. MT concentrations showed the same spatial and seasonal variation of Cd and were significantly related with total and heat-treated cytosolic Cd in all tissues. For Cu a significant relationship between MT and total or cytosolic Cu was only observed in the remaining tissues. No relationship was observed between MT and total or cytosolic Zn concentrations. Metals and MT concentrations increased with the increase in the condition index for the gills and the digestive gland and decreased from the remaining tissues.Cd concentrations in the gills increased only in the heat-treated cytosolic fraction while Zn in this fraction decreased. Thus Cd concentrations in this tissue displaced Zn from the MT-fraction, leading to a modification of the soluble/insoluble Zn ratio once total Zn concentrations remained unchanged. This modification reflects a perturbation in the normal metabolism in this tissue due to the excess of Cd present. With the exception of the gills, Zn subcellular distribution in the other two tissues was similar among sites and season. The model that describes the relationship between MT, metals, and weight in the gills, digestive gland and remaining tissues also indicates that Cd was the only metal that influence MT synthesis significantly in all the tissues. The induced and/or existent MT was sufficient to bind free Cd ions present in the cells, preventing any damage to cellular metabolism in this clam population. Therefore, MT in the gills and digestive gland of R. decussatus can be used as an early warning signal for Cd exposure and are a useful biomarker to assess the toxicological status of this population in the Ria Formosa lagoon.

Isolation and characterisation of metallothionein from the clam Ruditapes decussatus

Metallothioneins (MT) were obtained after purification from metal-exposed clams ( Ruditapes decussatus) using gel-permeation and ion-exchange chromatography. Four cadmium–metallothioneins (CdMTs) were resolved by ion-exchange chromatography and they all had similar molecular weights, high cadmium content and an absorption spectra indicative of the presence of characteristic CdS aggregates. The NH 2-terminal sequence suggests the presence of at least two class I clam MT isoforms. For the other two putative clam CdMTs isolated, the results of the amino acid determination were inconclusive. One was slightly contaminated and the other one had a blocked NH 2-terminal. These clam metalothioneins contain glycine, which seems to be a common feature of molluscan MT family and exhibited more similarity to oysters than to mussels. Further investigation on the inducibility of these isoforms will be necessary if clams are to be used as biomarkers of metal exposure.

Nitric oxide production by carpet shell clam ( Ruditapes decussatus) hemocytes

We have demonstrated that carpet shell clam ( Ruditapes decussatus) hemocytes produce nitric oxide (NO) in response to zymosan or bacterial lipopolysaccharide (LPS). This NO production was partially inhibited by the NO synthase inhibitor, N-ω-nitro- l-arginine (L-NAME). The capability of clam hemocytes to produce NO in response to the bacterial pathogen Vibrio tapetis was also studied. Incubation with bacteria induced a significant NO production by clam hemocytes, even though exogenous NO only slightly decreased the growth of V. tapetis. The effect of exogenous NO on the capability of clam hemocytes to phagocytose labeled Escherichia coli was studied using two different NO donors S-nitroso- N-acetyl-penicillamine (SNAP), and diethylenetriamine NO adduct (DETA/NO). Exogenous NO did not increase hemocyte phagocytosis, indicating that NO does not mediate phagocytosis in this species. These results are in accordance to those observed in other mollusk species, in which NO was independent of phagocytosis and constitutes an alternative method of killing invading pathogens.

Hypnospores detected by RFTM in clam ( Ruditapes decussatus) tissues belong to two different protozoan organisms, Perkinsus atlanticus and a Perkinsus-like organism

The development of hypnospores (large cells that stain dark blue with Lugol's iodine) after incubation of bivalves tissues in Ray's fluid thioglycollate medium (RFTM) has been used for Perkinsus diagnosis for the last 40 years. Polymerase chain reaction (PCR) was performed using conserved 18S rRNA gene primers on DNA from an enriched preparation of hypnospores obtained from carpet shell clam ( Ruditapes decussatus) tissues incubated in RFTM. The restriction analysis of the cloned 18S rRNA gene PCR fragments showed different band profiles. The DNA sequencing analysis of the PCR products confirmed that they corresponded to Perkinsus atlanticus and Pseudoperkinsus tapetis, morphologically very similar to Perkinsus spp. All the cloned fragments of the 18S rRNA gene obtained from the in vitro cultured P. tapetis gave only one restriction profile, leading us to conclude that the culture was axenic containing only this organism. Hypnospores, obtained from clam tissues incubated in RFTM belonged at least, to these two morphologically similar although molecularly different organisms. The lack of specificity of RFTM makes its use questionable for the diagnosis of Perkinsus in Galicia and maybe in other parts of the world.

Routes of TBT uptake in the clam Ruditapes decussatus. I. Water and sediments as vectors of TBT uptake

This study assesses the relative importance of water and sediments as vectors of TBT uptake in the sediment-dwelling suspension feeder, Ruditapes decussatus. Accumulation of TBT was determined in R. decussatus exposed for 60 days to moderately high but environmentally realistic levels of TBT in water (100 ng Snl −1) and sediments (0.8 μg Sn g −1 dw), separately or in combination, using constant-flow systems. The results indicate that this species accumulates TBT predominantly from water. Although some accumulation from sediments does occur, the processing of large amounts of water needed to sustain the filter-feeding habits of this species is a prime determinant of TBT uptake. The route of exposure is reflected in tissue distributions of TBT in R. decussatus. However, gills are the most important site for accumulation of TBT from water, irrespective of whether contaminated sediments are present or not.

Routes of TBT uptake in the clam Ruditapes decussatus. II. Food as vector of TBT uptake

Marine bivalves are exposed to contaminants via the aqueous phase, sediments and food. Nevertheless, the relative importance of these phases as uptake vectors of contaminants in these marine organisms has not been well studied. Phytoplankton concentrate contaminants from seawater and given their position at the base of most marine food webs, these algal cells may play critical roles in the transfer of contaminants to higher trophic levels. This study assesses the relative importance of microalgae as a vector of tributylin (TBT) uptake in the infaunal, suspension-feeding bivalve Ruditapes decussatus. Accumulation of TBT via the algal diet was determined by experimental exposure of R. decussatus to 14C-TBT labelled phytoplankton Isochrisis galbana, for a period up to 60 days. The digestive tract of these clams initially accumulates TBT preferentially from food. After a few weeks of exposure, internal remobilization results in a more widespread partitioning of TBT amongst tissues.

Organotin levels in the Ria Formosa lagoon, Portugal

AbstractOrganotin concentrations were measured in water, sediments and clams (Ruditapes decussatus) from 11 sites in the Ria Formosa lagoon, Portugal, in 1992–93. Results showed a marked spatial pattern of tributyltin (TBT) and dibutyltin concentrations. The highest organotin concentrations were observed at Olhão (site 5), where the most important fishing harbour of the Southern coast of Portugal is located.Results indicated that fishing vessels, moored in the harbour at Olhão (site 5), were the major source of organotin contamination to the lagoon. No significant seasonal trend was observed, suggesting a continuous input of organotin compounds throughout the year. In several areas of the lagoon the TBT burdens in R. decussatus could have deleterious developmental effects. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Response of antioxidant systems to copper in the gills of the clam Ruditapes decussatus

Copper (Cu) is an essential element for biological systems, however, when present in excess, is toxic. Metallothioneins can play an important role in Cu homeostasis and detoxification. Moreover, Cu can catalyse the production of toxic hydroxyl radicals that cause lipid peroxidation but defence systems in the cells can limit the oxidative damage. The present study was performed to investigate the effect of three Cu concentrations (0.5, 2.5 and 25 μg l−1) on the response of antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT), selenium-dependent glutathion peroxidase and total glutathion peroxidase), total proteins, metallothioneins (MT), malondialdehyde (MDA) concentrations in the gills of the clam, Ruditapes decussatus. The activity of antioxidant enzymes and total proteins, MT and MDA concentrations were measured in the gills of the clams after 1, 3, 7, 14, 21 and 28 days of Cu exposure. Results indicate that Cu only induces an imbalance in the oxygen metabolism during the first week of Cu exposure due to a decrease in mitochondrial SOD and CAT, selenium-dependent and total glutathion peroxidase activities. Cu also causes lipid peroxidation, measured by the MDA formation, that was Cu dependent. In the gills of clams exposed to 25 μg Cu/l, the excess of Cu triggers the induction of MT synthesis after 3 days of exposure.

Polymerase Chain Reaction–Restriction Fragment Length Polymorphism Analysis of a 16S rRNA Gene Fragment for Authentication of Four Clam Species

Specific identification of four clam species, Ruditapes decussatus (grooved carpet shell), Venerupis pullastra (pullet carpet shell), Ruditapes philippinarum (Japanese carpet shell), and Venerupis rhomboides (yellow carpet shell), was achieved by polymerase chain reaction–restriction fragment length polymorphism analysis of a fragment of the mitochondrial 16S rRNA gene. Amplification of DNA isolated from the foot muscle produced fragments of 511 bp for V. pullastra, 523 bp for R. decussatus, 545 bp for R. philippinarum, and 502 bp for V. rhomboides. The restriction profiles obtained by agarose gel electrophoresis when amplicons were digested with endonucleases BsmAI and BsrI allowed unequivocal identification of the four clam species. This approach would be less costly, simpler, and quicker than conventional sequencing of polymerase chain reaction products followed by detailed comparison of individual sequences, especially when large numbers of samples need to be analyzed.

Effect of cadmium on antioxidant enzyme activities and lipid peroxidation in the gills of the clam Ruditapes decussatus

Metals are known to influence the oxidative status of marine organisms, and antioxidant enzymes have been often proposed as biomarkers of effect. The clam Ruditapes decussatus is a well-known metal bioindicator. In this species cadmium (Cd) induces metallothionein (MT) synthesis only after 7 days of exposure. Before MT synthesis is induced, the other mechanisms capable of handling the excess of Cd are unknown. In order to identify some of these mechanisms, variations in antioxidant systems (superoxide dismutase, catalase, selenium-dependent glutathione peroxidase and non-selenium-dependent glutathione peroxidase), malondialdehyde (MDA) and MT were studied in the gills of R. decussatus exposed to different Cd concentrations (4, 40 and 100 gl-1) for 28 days. These parameters, together with total proteins and Cd concentrations, were measured in the gills of the clams over different periods of exposure. Results indicate that Cd accumulation increased linearly in the gills of R. decussatus with the increase in Cd concentration. This increase induces an imbalance in the oxygen metabolism during the first days of Cd exposure. An increase in cytosolic superoxide dismutase (SOD) activity and a decrease in mitochondrial SOD activity was observed at the same time as or after a decrease in cytosolic and mitochondrial catalase activity and of selenium-dependent and non-selenium-dependent glutathione peroxidase activity. After 14 days of exposure, Cd no longer affect these enzymes but there was elevation of other cellular activities, such as MDA and MT production. MT bound excess Cd present in the cell. These variations in these parameters suggest their potential use as biomarkers of effects such as oxidative stress resulting from Cd contamination in molluscs.

Comparison of Ribotyping, Randomly Amplified Polymorphic DNA, and Pulsed-Field Gel Electrophoresis for Molecular Typing of Vibrio tapetis

Brown ring disease, caused by Vibrio tapetis, is an important pathological problem in different species of cultured clams. In order to evaluate the genetic diversity of the pathogen, twenty-seven isolates of V tapetis with different origin were screened by ribotyping (RT), pulsed-field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA PCR (RAPD). Restriction with PvuII, SalI, and SmaI gave 2 RT patterns, differentiating in all cases the strain 0202RD isolated from carpet-shell clams (Ruditapes decussatus) from the other strains tested. The use of NotI generated strain specific PFGE profiles, which could be grouped in two main clusters. Cluster 1 grouped all but one strain and was subdivided into six PFGE subtypes (1a to 1f) which joined at a similarity level of 75.6%. Cluster 2 included again only the isolate 0202RD. RAPD analysis yielded the same results with three different primers, this method being able to differentiate the isolates from R. decussatus from those isolated from other clam species. Of the three techniques evaluated, PFGE was the most discriminating of the three techniques evaluated, followed in discriminating power by RAPD and RT tests. On the basis of the results obtained, we conclude that the RAPD procedure, which is more rapid and easier to perform than the other techniques, shows to be very useful to analyze large amounts of strain collections from an epidemiological monitoring stanpoint. In addition, PFGE is of great utility to evaluate the genetic diversity of strains involved in an outbreak and to study the spreading of a specific clone.

Pathogenicity of Vibrio tapetis, the etiological agent of brown ring disease in clams.

Brown ring disease (BRD) causes high mortalities in the introduced Manila clam Ruditapes philippinarum cultured in western Europe. The etiological agent of BRD, Vibrio tapetis, adheres to and disrupts the production of the periostracal lamina, causing the anomalous deposition of periostracum around the inner shell. Because the primary sign of BRD is found outside the soft tissues, the processes leading to death are not as obvious as those for internal pathogens. This study was designed to evaluate the pathogenicity of V. tapetis, in an attempt to help explain the mechanisms of mortality. We found high mortalities (up to 100%) for clams following the inoculation of V. tapetis into the extrapallial space (between mantle and inner shell) or the posterior adductor muscle of healthy R. philippinarum. Microscopy and immunological detection methods showed that the pathogen was rapidly eliminated from tissues and hemolymph of animals that survived the inoculation. In clams that died, the bacteria were found to have proliferated, resulting in severe tissue disruption. Bacteria were able to penetrate into tissues from the extrapallial space through the external epithelium of the mantle. In contrast, no mortalities were observed following injection of V. tapetis in the native European clam Ruditapes decussatus, which is resistant to BRD. This clam rapidly eliminated the bacterium from hemolymph and soft tissues. Clam mortality associated with BRD in the field is likely to result from the penetration of V. tapetis into the clam's extrapallial space through the disrupted periostracal lamina and from there into the soft tissues through the irritated mantle epithelium. Some bacteria also penetrate through the digestive epithelia. In either case, bacteria proliferate rapidly in the soft tissues, causing severe damage and subsequent death.

The use of acetylcholinesterase activity in Ruditapes decussatus and Mytilusgalloprovincialis in the biomonitoring of Bizerta lagoon

The variations of acetylcholinesterase activity, considered to be a biochemical biomarker of organophosphorus and carbamate compounds, was followed in Mediterranean clams ( Ruditapes decussatus) and mussels ( Mytilus galloprovincialis) as a function of season and sampling sites in the lagoon of Bizerta (Tunisia). Results show that acetylcholinesterase activity in clams collected from station A was the lowest and was so throughout the year. This low activity may be due to the input of non-treated waste waters in the lagoon. Heavy metal contamination has been reported in the sediments of this area, suggesting that acetylcholinesterase activity in clams may be inhibited by this type of pollution. Clams harvested from station F, a site adjacent to an agricultural area, were characterized by a decrease in acetylcholinesterase activity, especially after rain periods. Clams from station J presented the highest activity throughout the greater part of the year. This phenomenon may imply that this location is less affected by pollutants inhibiting AChE activity than the others. In the mussels from station C, located in the channel from the lagoon to the Mediterranean and submitted to pollutants (urban wastes from Bizerta and hydrocarbons from the maritime traffic), acetylcholinesterase activities were lower than in those from station J. In conclusion, the variations in acetylcholinesterase activity observed between stations in both species may be the result of pollution and of the environmental conditions.