Investigation of parasites and diseases affecting molluscs of ecological and economic interest is critical for the management of native stocks and aquaculture. In recent years, much attention has been devoted to investigating the World Organisation for Animal Health listed infectious diseases, so that communities can be prepared to attend public health emergencies and avoid severe income losses. In this context, the health status of Mytilus galloprovincialis Lamarck, 1819 was analysed in two aquaculture sites (Strunjan Bay and Piran Bay, Slovenia), and in four natural mussel beds (Adriatic Croatia International Marinas Pula and Rovinj and St Catherine, Croatia; Marina Koper, Slovenia) along the coast of the northern Adriatic Sea. The mussels were sampled in February and April 2014, and processed for histological examination of several endosymbionts and pathogens that frequently occur in mytilid mussels. Endosymbionts and pathogens were not detected in farmed mussels. Prokaryotic inclusion bodies, the protozoan Nematopsis, Ancistrocoma-like ciliates, haplosporidian-like plasmodia, turbellarian Urastoma cyprinae, and basophilic inclusion bodies were observed in digestive gland cryosections of wild mussels from the coastal region of the northern Adriatic. Fungal spores of Psilocybe sp., Ulocladium sp. and Alternaria sp. were detected between the digestive tubules based on their morphology. Diagnostic PCR did not reveal infection with Marteilia refringens during the studied period, neither in wild nor farmed mussels. We confirmed the site effects on prevalence of infected mussels. Thus, we can conclude that wild areas are more exposed to endobionts and parasites than aquaculture sites.

The concentrations of organophosphoric acid triesters (OPEs) in water samples from Maizuru Bay were in the range of 3.0–62 ng/l. In general, the concentrations of OPEs were found in the order of TBXP > TDCPP > TCEP > TBP > TCP > TPP > TEP. The organophosphorous pesticides (OPPs) diazinon, fenitrothion, iprobenfos and chlorpyrifos were detected in water samples. The concentrations of OPEs in sediment from Maizuru Bay were in the range of <0.5–56 µg kg−1 dry weight (dw). Among OPPs, diazinon in sediment samples were in the range of 1.8–71 µg kg−1 dw. However, the detection frequencies of fenitrothion and chlorpyrifos in sediment were low. The concentrations of OPEs in mussels from Maizuru Bay were in the range of <1–34 µg kg−1 wet weight (ww). The concentrations of OPEs were found in the order of TBP > TDCPP > TCP > TBXP = TPP = TCEP. Pesticides were detected in mussels, but these concentrations were lower than the acceptable daily intake (ADI) values. The partition coefficients between water and sediment (Kws) of diazinon and fenitrothion were 200–1300 and 200–300, respectively and the partition coefficients between water and biological samples (Kwb) of diazinon and fenitrothion were 700–3300 and 450–700, respectively, suggesting that these pesticides accumulate in biological samples at higher rates than in sediment.

Rocky shore intertidal communities along the cold- and warm-temperate coasts of the south-western Atlantic are dominated by small mussels of the genus Brachidontes s.l. (Mytilidae), yet the status of species occurring in the region remains unresolved. Taxonomic studies have been based on shell morphology, but high phenotypic variability has led to much confusion. Based on mitochondrial and nuclear genes (COI, 28S rDNA and ITS1) from nine localities in Uruguay and Argentina we confirmed the occurrence of three species in the south-western Atlantic: Brachidontes darwinianus and B. rodriguezii in the warm-temperate and B. purpuratus in the cold-temperate sector. The latter two species coexist in the same beds along the transition zone (41–43°S). The phylogeny based on mitochondrial and nuclear genes, indicate an early divergence of B. purpuratus. At the intra-specific level, low genetic differentiation and absence of fossil record for B. purpuratus from the earlier Quaternary marine terraces of Patagonia likely result from a relatively recent (post-LGM) colonization originated from populations in the south-eastern Pacific. In the case of B. rodriguezii, by contrast, genetic intraspecific differentiation, a fossil record of phenotypically-related forms going back to the Late Miocene, and phylogenetic position in the COI-based phylogeny, prompts the hypothesis that this species is derived from a local stock with a long history of occurrence in the warm-temperate region of the south-western Atlantic. While intertidal mussel beds from the south-western Atlantic are ecologically similar in appearance, their assembly involves components clearly differentiated in terms of historical biogeography and phylogeny.

Our study tracked three non-native, marine, sessile, invertebrate species which have recently colonized the south-eastern United States Atlantic coastlines and estuaries: Mytella charruana, the charru mussel; Perna viridis, the Asian green mussel; and Megabalanus coccopoma, the titan acorn barnacle. Along the eastern Floridian coast, Mytella charruana was discovered in the Indian River Lagoon, Florida (FL) in 2004. Perna viridis was found in Ponce de Leon Inlet, FL in 2002, after being introduced to Tampa Bay, FL in 1989. Megabalanus coccopoma was documented in St Augustine, FL and Brunswick, Georgia in 2006. From 2006 through to 2011, a biannual survey of the south-eastern Atlantic coastlines and estuaries was conducted from Jupiter, Florida to Charleston, South Carolina (894 km) to document the distribution and range expansion of M. charruana, P. viridis and M. coccopoma. Field surveys were conducted in June and December each year at 82 sites (e.g. docks, boat ramps, jetties and mangrove roots). The ranges of the three invertebrates have expanded and retracted along the Atlantic coast since the survey began. Mytella charruana had spread as far north as Savannah, Georgia in 2007, but the species was absent from northern Georgia in 2010 and 2011. Perna viridis and M. coccopoma were present in Georgia in 2007, but were absent in the 2010 and 2011 surveys. These range fluctuations may be explained by extreme cold temperatures, which occurred during the 2009/2010 and 2010/2011 winters. The patterns observed with these three sessile invertebrates provide information regarding how non-native species disperse and establish in new locations.

This study presents the morphological description and histochemical characterization of gill filaments of the Brazilian endemic bivalve Diplodon expansus, aiming to broaden the morphological knowledge of this species and establish the structure of the gills that will serve as control in histopathological studies applied to biomonitoring. The gill filaments are divided into three zones: frontal, intermediate, and abfrontal. In the center of the filament, haemocytes circulate through the haemolymph vessel, which is internally lined by endothelium. The frontal surface of the filament is covered with cilia, the lateral surface exhibits aquifer ducts, and the abfrontal surface presents ciliated and nonciliated cells. The epithelium of the filaments is composed of ciliated cells, nonciliated absorptive cells, and mucocytes. The support of the filaments is made by two specialized structures called skeletal rod and skeletal loop. Based on the obtained information, the gill filaments of the studied species present some peculiar characteristics that are not yet reported in detail in the literature such as the simultaneous presence of skeletal rod and skeletal loop. On the other hand, the general constitution of the filament is similar to that described for both marine and limnic bivalves and seems to be suitable for ecotoxicological studies.

This study aimed to examine the responses of RNA/DNA ratio in Perna viridis under different nutritional status via both field and laboratory studies, and hence evaluate the usefulness of this ratio as a rapid growth biomarker in the mussels. First, the effects of size (small: 30–40 mm; medium: 40–50 mm; large: >50 mm) and tissue type (adductor muscle, foot, gill and hepatopancreas) on the RNA/DNA ratio were investigated in P. viridis collected from three different sites with different degrees of eutrophication in Hong Kong waters. Across all sizes, the mussels collected from a fairly ‘eutrophic’ mariculture zone had significantly higher RNA/DNA ratios in their gills than those from the other two relatively clean sites. The RNA/DNA ratio in small mussels was generally higher than in medium and large individuals, though such a size effect significantly interacted with tissue type and site. Second, we conducted a 10-day comparative laboratory study to elucidate the influence of starvation and feeding on the RNA/DNA ratio in the mussels. We observed that both hepatopancreas and foot muscle generally exhibited significant and rapid response to such a short-term starvation or food addition. The present results confirmed that the RNA/DNA ratio in P. viridis is a sensitive biomarker to gauge their growth and general health condition in accordance with food availability and/or eutrophication condition.

The processes involved in vital effects, defined as biological processes overriding environmental signals, are not well understood and this hampers the interpretation of environmental parameters such as seawater temperature. Insufficient knowledge is available about changes in physico-chemical parameters, in particular those related to crystallography, associated with biomineral formation and emplacement. This paper assesses the influence of crystallography on Mg2+ concentration and distribution in calcite biominerals of bivalved marine organisms, mussels and rhynchonelliform brachiopods, and considers the implications for Mg/Ca thermometry. In the mussel Mytilus edulis, changes in Mg2+ are not associated with crystallography; but in the brachiopod Terebratulina retusa, increases in Mg2+ concentrations (∼0·5–0·6 wt. ) are associated with the {0001 planes of calcite biominerals. A comparison between mussels and brachiopods with avian eggshells, which form at constant ambient temperature, also reveals that there is at least a common 0·1 wt. variation in magnesium concentration in these calcite biomineral systems unrelated to temperature or crystallography. Results demonstrate that the integration of contextual crystallographic, biological and chemical information may be important to extract accurate environmental information from biominerals.

The objective of this study was to identify a possible effect of food on the accelerationof decontamination in blue mussels, Mytilus edulis, containing diarrhetictoxins belonging to the okadaic acid (OA) structural group. An experimental protocol wasdesigned to describe and compare the decontamination kinetics and detoxification rates ofnaturally OA-contaminated mussels that had either received or not received food for threeweeks. The protocol was applied in two trials (in June 2006 and June 2007, called Ker06and Ker07), conducted one year apart on samples of mussels collected in the same area, atthe same season. Okadaic acid (OA), the main lipophilic toxin produced by the toxic algaDinophysis acuminata, was analysed over the course of thedecontamination, in hydrolysed (total OA) and non hydrolysed (free OA) digestive glandextracts, in order to estimate acyl-esters (7-O-acyl-ester derivatives ofOA) concentrations. OA analyses were also made for toxin presence in biodeposits and inthe aqueous phase. Bivalve physiological status was evaluated by biomass measurements (dryweight of flesh) and two biochemical compounds (total lipid and glycogen concentrations).Measured physiological parameters showed that mussels did not suffer under experimentalconditions. Both trials showed that the food accelerated the elimination of free and totalOA. This effect cannot be attributed to a dilution of the toxin in the tissue, as resultsexpressed in toxin burden led to the same conclusion. The kinetic models ofdecontamination differed between the two experiments: the model was linear for Ker06,provided that the values corresponding to the first two days were discarded, whereas datafitted a decreasing exponential curve better in Ker07. Detoxification rates increased asthe food supply increased. After three weeks of experimentation, the detoxification ratesfor total OA in Ker06 and Ker07 were 52 and 61%, respectively, in unfed mussels and 90 and89% in fed mussels (with the highest level in Ker07). Comparisons between the free OA andesters showed that detoxification rate was higher for free OA than for esters, whateverthe level of food supply. The results of this study suggest that food increase probablyaccelerates elimination of OA and OA-esters but the latter are eliminated at a lowerspeed.

During a parasitological survey of the brown mussel Perna perna from highly productive culture fields in the southern sector of Brazil, monstrilloid copepods were discovered in the mantle of this mytilid bivalve. Numerous specimens of endoparasitic copepods were found within nodules in the mantle of the host; they belong to an undetermined species of Monstrilla. Monstrilloid copepods were known to be endoparasitic in polychaetes and in one species of prosobranch mollusc only; their occurrence as parasites of bivalve molluscs has not been previously documented. This is also the first record of these crustaceans infecting commercial molluscs. The prevalence of Monstrilla sp. infecting the brown mussel was 25.6%. At the histological level, it was observed that the larvae induced a strong haemocytic infiltration resulting from the complete larval encapsulation within the host mantle. The effect of this monstrilloid in the cultured populations of P. perna deserves further study.

Electron backscatter diffraction (EBSD) is becoming a widely used technique to determine crystallographic orientation in biogenic carbonates. Despite this use, there is little information available on preparation for the analysis of biogenic carbonates. EBSD data are compared for biogenic aragonite and calcite in the common blue mussel, Mytilus edulis, using different types of resin and thicknesses of carbon coating. Results indicate that carbonate biomineral samples provide better EBSD results if they are embedded in resin, particularly epoxy resin. A uniform layer of carbon of 2.5 nm thickness provides sufficient conductivity for EBSD analyses of such insulators to avoid charging without masking the diffracted signal. Diffraction intensity decreases with carbon coating thickness of 5 nm or more. This study demonstrates the importance of optimizing sample preparation for EBSD analyses of insulators such as carbonate biominerals.

The present study reports on population dynamics and growth performance relative to a lesser known exotic invasive species (Brachidontes pharaonis) inhabiting the southern Mediterranean. The study was carried out in western Sicily, where B. pharaonis is present on both the submerged and emerged surfaces of a hyperhaline saltpan. Individuals were scraped, counted and measured for shell length, total weight, somatic, gonadic and shell biomass. Brachidontes pharaonis intensively colonized all hard substrates of the saltpan with annual average densities of 375 ± 293 ind. 400 cm−2 with density peaks in autumn as a function of habitat. The occurrence of juveniles was different for mediolittoral and infralittoral populations as was mean size, spawning periods and annual organic matter biomass. Organic matter allocated to the shells represented 56.4% (of the total), gonad allocation was 7.3%, while somatic allocation averaged 36.3% for both populations. Brachidontes pharaonis reached high individual density, rare among temperate members of the genus Mytilus in Mediterranean and European waters, but common in tropical dense mussel beds. Considering its invasive potential and the recent warming trend of the Mediterranean, in the future B. pharaonis may actively invade more habitats, threatening indigenous bivalve species which may be unable to compete with B. pharaonis in terms of reproductive effort and density.

The petroleum spilt by the tanker “Erika” contained environmentally high concentrations of nickel (45 mg kg−1) and vanadium (83 mg kg−1). Our aim was to show that nickel and vanadium concentrations in marine organisms could be used as tracers of their exposure to oil deposits along the coast. Two biomarkers were determined, condition index (CI) and metallothionein levels.Samples were collected monthly from January to May 2000 from five sites along the coast of Vendée and Loire Atlantique: (1) Lérat, (2) La Govelle, (3) Saint Gildas, (4) La Bernerie and (5) La Fosse. Among benthic invertebrates, mussels Mytilus edulis (filter-feeders), periwinkles Littorina littorea (grazing-feeders) and dogwhelks Nucella lapillus (carnivora, bivalve predators) were selected. In addition, mussels were collected from a control site, Fier d'Ars (Ré Island). The species chosen as bioindicators have responded to the presence of oil in their environment by accumulating nickel and vanadium. The bioaccumulation of vanadium occurred early one month after oil spill whereas nickel bioaccumulation was deferred, probably as a consequence of a lower stability of vanadylporphyrins compared to nickelporphyrins which are known in particular for their role in stabilizing emulsions (film at the water/oil interface). Interspecific differences may be explained by different food habits: periwinkles grazed contaminated algae; mussels as filter-feeders retained particles and colloids from the water column; dogwhelks fed on mussels. Spatio-temporal changes of nickel and vanadium concentrations may result from (i) the arrival of new oil slicks, (ii) the action of cleaning of the coasts contributing to the re-suspension of petroleum. In all of the three species, few changes of the CI were observed from site to site. CI variations were linked to sexual ripening in mussels. Mussels originating from the control site showed MT concentrations significantly lower than those in specimens from impacted sites. The highest MT concentrations were observed in January and February, and then a consistent decrease was registered in March and May. MT concentrations in periwinkles increased very significantly in March and May. An increase in MT concentrations was also shown at this period in dogwhelks. Depending on the species, positive correlations were shown between MT and nickel and/or vanadium concentrations.

A 3-year survey was made of several biological markers in mussels (Mytilus edulis) exposed in situ to the oil that came ashore after the wreck of the “Erika” tanker on the Brittany (France) coast in December 1999. The mussel response was assessed using a set of 7 biomarkers, most of them related to the metabolism of organic contaminants. After a series of validation tests, data was evaluated for only 5 biomarkers: acetylcholinesterase (AChE), glutathione S-transferase (GST), catalase (CAT), malondialdehyde (MDA) and deoxyribonucleic acid (DNA) adducts. No significant reductions in GST or CAT levels were observed, levels of DNA adducts and MDA were high during the 6 months immediately following the accident and levels of AChE were significantly lower during the first year of the survey suggesting a general stress. A simple multivariate graphic method, the integrated biomarker response index, was used to combine 4 of the 5 validated biomarkers and quantify the degree of impact on mussels at different sites. The results show that mussel populations were affected by the oil spill only during the first year after the event.

Levels of nickel and vanadium, trace metals found in high concentration in the oil spilled from the “Erika” tanker off Brittany (France) in December 1999 (41 ± 1 and 87 ± 3 mg kg−1 respectively), have been monitored over a one-year period following this accidental event in several benthic invertebrates. Ni and V in mussels (Mytilus edulis) and oysters (Crassostrea gigas) soft tissues were analysed twice a month by graphite furnace atomic absorption spectrometry and a scallop (Pecten maximus) shell daily growth bands were sampled every three bands by laser ablation and analysed by ICP-MS for these two contaminants. Survey data for mollusc tissues were compared with reference data arising from the national monitoring database. Ni concentrations in dried tissues, comparable with reference data (1.8 ± 0.9 µg g−1 in mussels and 1.2 ± 0.5 µg g−1 in oysters) do not show any additional input during the whole period. Conversely, a sharp increase in vanadium concentrations (up to 4.6 and 3.2 µg g−1 for mussels and oysters respectively) is observed around May 2000, i.e. 5 months after the wreck, compared with the monitoring data (1.4 ± 0.6 µg g−1 in mussels and 1.3 ± 0.6 µg g−1 in oysters). Furthermore, no Ni peak is detectable in the time profiles of scallop shell growth bands where a V peak is observed also in May 2000. This study shows that although a “mussel-watch-type” network, based on the monitoring of vanadium concentration in mollusc tissues, is able to identify contamination due to oil spills, similar information might be obtained a posteriori by analysing daily growth bands of scallop shells.

Mussel (Mytilus galloprovincialis) plasma contains cytotoxic activity against both vertebrate (erythrocytes and mouse tumour) and protozoan cells. Procaryotes (Escherichia coli and Vibrio alginolyticus) were not sensitive to the cytotoxicity. The activity was still present in dialyzed samples but was inhibited by heating at 45 °C. Large individual variability which was not correlated with protein concentration and an increasing number of reactive specimens following injection, suggested that naive mussels were in various stages of immune response. Purification by anion exchange chromatography followed by gel filtration revealed a 320 kDa cytotoxic polymeric protein that acts through a polymerization process after binding onto target cell membranes as revealed by ultrastructural observation.

European and Pacific oysters (Ostrea edulis and Crassostrea gigas) expressed antibacterial activity against both Gram negative and Gram positive bacteria which was most probably due to small proteins. When tested against the marine pathogenic Vibrio alginolyticus, hemocyte lysates of both species were more active than cell-free plasma. Antibacterial activity showed significant individual variability that was dramatically reduced by stimulation through mechanical stress or injection. The number of spontaneously active Pacific oysters increased from 50 to 100% following a single injection of bacteria.

These results strongly support the view that bivalve molluscs possess sensitive immuno-defense mechanisms that will greatly aid the development of aquaculture systems by employing refined techniques of transgenesis.