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Information on the occurrence and bioaccumulation of bisphenols and benzophenones in coastal marine invertebrates is limited. In this study, concentrations of eight bisphenol and five benzophenone analogues were determined in 186 mollusks collected from coastal areas of the Chinese Bohai Sea during the period 2006–2015. Total concentrations of bisphenols and benzophenones were in range of not detected (nd)–58 (geometric mean: 13.0 ng/g) and nd–59.1 (2.06 ng/g) on a dry-weight basis, respectively. BPA and BPF were the major bisphenols, collectively accounting for >90% of the total concentrations. BP-3 was the predominant benzophenone, representing 74% of the total concentrations. The mollusk species, Meretrix meretrix, accumulated high concentrations of both bisphenols and benzophenones. A steady increase in bisphenol concentrations in mollusks was observed in recent years, whereas no obvious temporal trend was found for benzophenones. The estimated daily intakes of bisphenols through consumption of mollusks were lower than the current reference dose. This study establishes a baseline concentration for bisphenols and benzophenones in mollusks in Chinese coastal waters.

To evaluate the pollution level of marine environment received treated municipal effluent (TME), the water quality classification index (WQCI) capable of integrating biomarker results into a four-level pollution for effluent assessment was proposed and applied. The WQCI calculation was that of the integrated biomarker responses vesion 2 (IBRv2) index based on the expert system classification scale. In this research, mussels of Meretrix meretrix were treated with different effluent volume ratios (EVRs, 0–40%, v/v) for 12 days, six biomarkers of oxidative stress, metal exposure and neurotoxicity in both gills and digestive glands as well as the other two biomarkers of general health and genotoxicity in hemocytes were measured. Then based on the correlation analysis between the response of biomarkers and EVRs, the lysosomal membrane stability (LMS) and micronucleus frequency (MF) in hemocytes, glutathione (GSH) and acetylcholinesterase (AChE) in gills were chosen to calculate the IBRv2 and WQCI. The results showed that the control (EVR = 0%) was defined as Level I, EVR of 1–5% as Level II, EVR of 10–30% as Level III, and EVR of 40% as Level IV. In addition, two other sets of data of biomarkers in previous studies were used to test the applicability of the classification scheme established. The WQCI values and the evaluation results based on them were almost identical to those obtained by using the first set of data. This study is the first attempt to develop an index on water quality assessment of marine environment received discharged effluent from a biological perspective. The findings confirm that WQCI offers a potential measurement of water quality evaluation of marine environment and possible to be a water quality standard.

Microplastics ingested by two bivalve species Perna viridis and Meretrix meretrix collected from three estuaries viz. Ariyankuppam, Panithittu, and Chunnambar in Pondicherry, India was analysed for the first time in this research. Nile Red dye was used for microplastic detection. A survey of 50 local families was conducted to determine the frequency and quantity in which they consume mussels/clams. On an average, the number of microplastics per gram of soft tissue (wet weight) is 0.18 ± 0.04, 1.84 ± 0.61, and 1.76 ± 0.48; and the number of microplastics per bivalve is 0.50 ± 0.11, 1.75 ± 0.35, and 4.80 ± 1.39 respectively for Ariyankuppam, Panithittu, and Chunnambar. 61.02% and 77.42% of the particles belonged to the size group of100 μm in M. meretrix and P. viridis respectively. A moderate positive correlation of r (18) = 0.6985, p 0.05 was calculated between bivalve weight and microplastic particles. An average person belonging to the local community is likely to ingest 3917.79 ± 144.71 microplastic particles per year through mussel consumption.

This paper presents results of a laboratory study designed to assess the impact of pollution in Espirito Santo Estuary, Mozambique, by the use of scope for growth (SFG) and condition indices in the clam Meretrix meretrix . Low energy balances were observed at all sites from the estuary (0.91–2.89 J h −1 g −1 ) as well as from the comparison site (2.57 J h −1 g −1 ). Lowest condition index was observed in clams from the comparison site. Results from the present study indicate symptoms of stress and impact of pollution, and whether M. meretrix is a suitable candidate species for further studies of environmental contamination in coastal regions. This study is to our knowledge the first to investigate the energy available for growth in M. meretrix in its southern area of distribution.

Because of the high frequencies of null alleles at microsatellite loci in mollusks, it is difficult to enhance the accuracy of parentage assignment in closely related families by increasing the number of loci. To develop an effective approach, microsatellite markers combined with mitochondrion COI marker were used for parentage assignment with computer simulations and experimental verification in the clam, Meretrix meretrix. In the present study, simulations based on allele frequency data from the candidate parents (sample II) demonstrated that combined exclusion probability of the five microsatellite loci (0.991 for Excl 1 and 0.995 for Excl 2) were not much lower than that of the seven loci (0.993 and 0.999). After discarding the two loci that deviated from Hardy-Weinberg equilibrium in experimental verification, accurate probability of progeny assigned to their fathers and mothers with both parents unknown was 68% and 59% in CF (closely related families), and 76% and 68% in DF (distant related families), respectively, which were much lower than those predicted by the simulations. When the COI marker was used in combination with microsatellite markers, 32 out of 39 offspring that were not previously assigned to their correct parents were assigned to their correct mothers, and 29 doubtful offspring could be assigned to their correct fathers. Consequently, with the combination of the two kinds of markers, the accurate probability of progeny that can be correctly assigned to their true fathers and mothers was increased to 89% and 92% respectively. We suggest that the use of microsatellite markers and COI marker will greatly improve the efficiency of parentage determination in closely related families in the clam. (C) 2011 Elsevier B.V. All rights reserved.

All structural biological materials are nearly composite materials and often exhibit some superior properties. In order to obtain useful information for the design and manufacture of composite materials, the microstructures and the friction-wear properties of three species of bivalve shells were studied in this paper. The results showed that the microstructure of tested bivalve shells I ( Meretrix meretrix ) and II ( Saxidomus purpuratus ) are constructed of about 10–100 μm small platelets stacked in brick-and-mortar fashion and small platelets consist of lamella clusters. The lamellae are parallel inside the individual cluster. The orientations of adjacent lamellae clusters form the angle of about 70–90°. The thickness of lamellae is about about 0.2–0.6 μm. The organic component and the calcium carbonate form the three-dimensional net-like microstructure, respectively, which interlaces each other to form the microstructure of the bivalve shells. The microstructure of bivalve shells III ( Periglypta chemnitzii ) is constructed of about 10–40 μm particles with the internal structure of lamellae clusters as the above mentioned. Under the experimental conditions of medium-carbon steel counterpart and sliding dry friction, the friction coefficient of the bivalve shells is lower than that of grey cast iron HT200. The organic component of the bivalve shells can transfer to the friction interface and form organic film, which not only lubricates the friction interface but also protects the friction surface. The organic component is very important to the friction-wear property of the shells.

A nature-simulating culture system was used to explore the influence of salinity, the diurnal cycle and daylength on ingestion rate (IR) and assimilation efficiency (AE) of Meretrix meretrix . The clams used in the experiments were grouped into three sizes: small, with a shell length of 2.70 ± 0.10 cm and a dry fresh weight of 0.35 ± 0.04 g; medium, with a shell length of 4.00 ± 0.05 cm and a dry fresh weight of 1.25 ± 0.05 g; and large, with a shell length of 5.00 ± 0.10 cm and a dry fresh weight of 2.45 ± 0.10 g. The clams in all size groups demonstrated a common response pattern in IR and AE under salinities ranging from 18 to 34 ppt. The clams achieved the greatest IR within the salinity range 27 to 30 ppt. There was a marked reduction in IR outside this range. Of the salinities tested 18 ppt was the harshest stress to the feeding of M. meretrix . Between the salinities 24 to 34 ppt, changes in AE of the clam were the inverse of those observed in IR, suggesting that M. meretrix is able to compensate for the loss of IR by an increase in AE. Although the effect of both salinity and body size of the clam was significant on both IR and AE, salinity had evidently stronger influence than body size. All sizes of clam showed a three-phase diurnal feeding pattern: a high ingestion phase from 00:00 to 08:00, a low ingestion phase from 12:00 to 20:00, and a changing phase between low and high ingestion phases. The IR response to daylength comprised a high and constant feeding phase at daylengths from 0 to 16 h (longer darkness) and a declining and unstable feeding phase as daylength increased from 16 to 24 h (shorter darkness). All sizes of clams demonstrated an inverse adaptation to AE compared with IR, indicating that the clam is able to achieve a stable feeding physiology by compensating for daylength-induced variations in IR by changing AE. The ANOVA analysis also showed that both diurnal cycle and daylength affected IR and AE of the clam very significantly, body size did not, however.

The effects on reduced glutathione (GSH) levels, glutathione-S-transferases (GST) and glutathione peroxidase (GPx) activities of digestive gland in Meretrix meretrix exposed to tributyltin (TBT) at environmental levels (0.1, 1, 10 ng/L as Sn), in experimental condition, were evaluated. The GST activities in 0.1 ng/L groups were significantly elevated after exposure for 2 days, and were significantly inhibited after exposure to 10 ng/L TBT for 8 and 20 days. The GPx activities were mainly induced by TBT exposure, except the GPx activities in 10 ng/L groups were significantly inhibited after exposure for 2 days. The GSH content was significantly decreased with prolonged exposure. The GSH content, GST and GPx activities in all exposure groups, transferred to clean recovery tanks for 20 days, were recovered to the level corresponding to that of the control group. Taken together, our present studies indicate that exposure to TBT may induce strong production of reactive oxygen species in the clams.

The hydrocarbon levels in the clam Meretrix meretrix at selected locations along the Saudi Arabian Gulf coastline for the period 1981–90 (prior to the 1991 Gulf War) are compared to those from the war and post-war periods. Five of the nine sites in the study were affected by the war oil spill. There was no significant impact in the n -alkane levels. However dibenzothiophenes and phenanthrenes increased significantly in the clam tissue during the war period. These values returned to pre-war levels after a short period of time (within two years). The data from the sites affected by the oil spill are compared with data from the other four unaffected sites in the study that are located further to the south.

Clams (Meretrix meretrix) were collected during April–May 1991 (post-war period) from five locations along the Saudi Arabian coast of the Gulf. All the soft tissue from each clam was removed and digested separately at 120°C for 3 h in the nitric-perchloric acids mixture. Twenty metals were determined in the acid digests using an inductively coupled plasma analyser. Clams (Meretrix meretrix) were also collected from the same stations in April–May, 1985 (pre-war period) and analysed for Cd, Co, Cr, Mo, Ni, Pb, V, and Zn. Wherever appropriate, these data were compared with those collected in this study. Sediment and seawater samples were also collected during clam sampling. Concentrations of selected metals were determined in the sediment and seawater samples. Concentrations of Ba, Ca, K, Mg, P, and Sr were affected significantly (p

1. 1. An adenosine aminohydrolase was extracted from the mid-gut gland of the clam, Meretrix meretrix lusoria (Gmelin), in a highly purified form which, though heat-labile, could be stored over a month at 0°C without losing the specific activity amounting to 750-fold. 2. 2. The preparation catalysed the reaction of the first order, with the activation energy of 14,600 cal under the experimental conditions, showing the velocity constant of 13·18 × 10 −2 min −1 . 3. 3. A sharp optimum was found at pH 5·0. The Michaelis-Menten constant was 6·9 × 10 −5 M at 26°C at the optimal pH. 4. 4. This enzyme specifically decomposes adenosine and deoxyadenosine. Mercury, either metallic or organic, and fluoride inhibit the enzymatic reaction, though many common agents are not foond effective.

1. 1. A precipitate of water-homogenized midgut gland was suspended in 3 M NaCl, heat-shocked (50°C, 5 min), dialyzed against 0·2 M NaCl and suspended in 3 M NaCl to obtain a preparation with 17·7-fold activity of dephosphorylating 5′-AMP. 2. 2. It decomposed 2′-, 3′- and 5′-AMP, 5′-dAMP, 5′-UMP, 5′-IMP, 5′-GMP, 5′-CMP, 5′-ADP, ATP, β-glycerophosphate and p- nitrophenyl phosphate at pH 8·8, but did not attack l -α-lecithin and sodium creatine phosphate.

1. 1. Phosphohydrolytic activity was studied in the homogenized mid-gut gland tissue, using nucleotides (5′-AMP, 3′-AMP, 5′-IMP and GMP) and β-glycerophosphate as substrates. 2. 2. For nucleotides there were two optima of pH (8·5–9·7, 4·0–4·2). For β-glycerophosphate the activity was restricted to the alkaline region (pH 9·5).