The presence of the L-shaped shell deformity (LSSD) is a reliable biomineral marker for non-lethal detection of wild blue mussels ( Mytilus spp.) infected with the unicellular photosynthetic microalgae Coccomyxa sp. However, the LSSD formation rate is unknown. Most literature regarding bivalve shell sclerochronology advocates the fluorochrome calcein as an ideal growth marker. Administration technique of calcein-seawater solution for mussels, injection into mantle cavity or immersion, influences mark quality and staining. The best technique cannot be predicted in advance. Three circumstances may impact the dyeing success for Coccomyxa-infected mussels: mantle colonization with algae, increase in mucus production and biophysiological control in alga- mussel association. This report examines how injection (in field condition) and immersion (for 2 h- field condition; 20 h- laboratory condition) affect shell marking in adult (60-70 mm shell length) Coccomyxa-infected Mytilus spp. Uninfected wild and farmed mussels are used in parallel experiments for comparative purposes. After the staining procedures (calcein concentration 150 mg L-1), mussels were caged for 55 days in the Lower St. Lawrence Estuary (Quebec, Canada). Results demonstrate that uninfected mussels showed fluorescent marks regardless of the administration techniques, whereas in Coccomyxa-infected mussels marks were visible only after immersion for 20 h. This may suggest that dyeing success could be managed by unknown aspects of biophysiological control in alga-mussel symbiosis. A comparison of images made in 2019 and 2023 indicates no change in calcein marks brightness 4 years after the end of shell staining experiments.

Given the ability of engineered metal nanoparticles to be transformed in natural waters in unpredictable manners, various sampling methods must be developed. Here, we took a novel approach to collection silver nano particles (AgNPs) that involved the use of the intact periostracum, the outer proteinaceous organic layer, of freshwater unionid mussels Pyganodon sp. Eight adult mussels were collected in August 2019 from a small boreal lake (L222) at the International Institute for Sustainable Development Experimental Lakes Area (northwestern Ontario), which had been dosed with 15 kg of poly(vinylpyrrolidone)-coated silver nanoparticles (PVP-AgNPs) in 2014-2015. Additionally, three adult mussels were collected from a control lake (L375). Numerous silica (SiO2) diatom frustules were adhered to periostracum of all mussels. Intact periostracum promotes the formation of layer composed of diatoms and sand grains. The Ag content in soft tissues and shells of the mussels from L375 was as low as & LE; 0.1 mu g/g. In mussels from L222, Ag concentrations in the periostracum of five shells were in detectable amounts (1-4 mu g/g); in three shells concentrations were as high as 86, 122, and 494 mu g/g. The underlying mineral shell is depleted in Ag (< 0.1 mu g/g). The Ag content in soft tissue organs (whole body) ranged from 44 to 191 mu g/g. AgNPs occur on the surface of both periostracum and diatoms. Single AgNPs (d = 20-60 nm) were partly sulfidized to Ag2S. The observed AgNPs often form aggregates with an average and a maximal size of circa 100 nm and 1.5 mu m, respectively. Scraping small fragments of intact periostracum of unionid shell is non-lethal to mussels, and is easy to do under field conditions. This simple sampling protocol could be used to detect metal-based nanoparticles (engineered or accidental) with the use of unionid and dreissenid bivalves.

A survey of the exchange of freshwater gastropods mollusks between Europe and North America is provided. Several dozen species of snails migrated, during the last two centuries, in either direction across North Atlantic and this process is ongoing. The intensity of the faunal exchange is unequal since much more snail species have dispersed from North America to Europe than in the opposite direction. Two cases of "failed" invasions of North American lymnaeid snails to Europe are discussed. A species of pulmonate snails, Ampullaceana balthica (Linnaeus, 1758), is reported here as new for the malacofauna of Canada (and for the whole North America). This snail of European origin was found in June 2019 in a small lake in the vicinities of Rimouski Town (Quebec, Canada). The taxonomic identification of the mollusks was confirmed by molecular analysis, with the studied specimens having two unique COI haplotypes, hitherto not found in Europe.

As evidenced from literature, exposure to non-lethal concentrations of dissolved copper (Cu2+) and copper nanoparticles (CuO NPs) promotes blue mussels susceptibility to various bacterial infections. We study whether pre-exposure (3.5 h) with CuSO4 (100 ?g Cu L-1) and CuO NPs (1000 ?g Cu L-1) will result in infection of M. edulis L. with pathogenic microalga Coccomyxa sp. under field conditions. In May ? September 2019, cages were installed in the site Metis-sur-Mer, St. Lawrence Estuary (QC, Canada) where the native mussel population is known to be infected with the pathogen. Untreated and pre-exposed mussels were grown for up to 130 days. Only the mussels pre-exposed to copper were infected by Coccomyxa. This finding allows proposing that occurrences of Coccomyxa-infected mussels worldwide might have an association with water pollution with xenobiotics. Pre-exposure of caged mussels to copper, as a protocol monitoring for other infectious agents, can be recommended to test.

In several parts of the world, mytilid mussels, Mytilus spp., are infected with pathogenic, single-celled, photosynthetic algae belonging to the genus Coccomyxa. The posterior shell edge of heavily infected mussels becomes considerably thickened with an extra shell material. Also, the external shell surface is usually eroded as a result of the microboring activity of endolithic cyanobacteria. We compared the number of bioeroded shells, the bioerosion degree, and the number of badly eroded shells, in uninfected and Coccomyxa-infected Mytilus spp. from the Lower St. Lawrence Estuary, Québec, Canada. The thickness of prismatic and nacreous layers was measured. The epibionts (pink calcareous algae, crustose brown algae, and barnacles) which encrusted surface of studied shells, were counted. Epibionts did not occur frequently and their possible relationship with the partners of a three-way symbiosis, Coccomyxa sp. – Mytilus spp. – endolithic cyanobacteria, has been neglected. We suggest that the mussel provides the alga Coccomyxa a protected space and metabolic carbon for photosynthesis. The alga stimulates shell thickening, and this protects mussel against ocean acidification and predators. The endolithic cyanobacteria remove black-colored periostracum providing the mussel and alga with an increased ability to survive during sunny days when exposed at low tide. The eroded shells become more translucent which encourages alga photosynthesis. However, shell degradation caused by endolithic cyanobacteria is a possible reason for the death of the Coccomyxa-infected mussels at the studied sites.

Following the Fukushima Daiichi nuclear power plant accident in 2011, some marine radionuclide monitoring studies report a lack of evidence for contamination of Japanese coastal waters by U and Pu, or state that marine contamination by them was negligible. Nevertheless, Fukushima-derived U and Pu were reported as associated with Cs-rich microparticles (CsMPs) found in local soil, vegetation, and river/lake sediments. Over time, CsMPs can be transported to the sea via riverine runoff where actinides, as expected, will leach. We recommend establishing a long-term monitoring of U and Pu in the nearshore area of the Fukushima Prefecture using marine bivalve mollusks; shells, byssal threads and soft tissues should all be analyzed. Here, based on results from Th biosorption experiments, we propose that U and Pu could be present at concentrations several times higher in shells with a completely destroyed external shell layer (periostracum) than in shells with intact periostracum.

In August 2019, visual inspection of intertidal zones of the Gulf of Maine (ME, USA) revealed young and adult wild blue mussels, Mytilus spp., in Alley Bay (Jonesport area) with the distinctive L-shaped shell deformity (LSSD) and green spots (GS) in the mantle and adductor muscle. LSSD is a characteristic sign of current or previous mussel infection by photosynthetic unicellular alga from the group Coccomyxa, while GS are algal colonies. Based on these findings, this study represents the first report of infection signs by pathogenic Coccomyxa-like algae in mussels from the coastal waters of the Northeastern United States, providing a base for future large scale monitoring of the alga in the region.

An L-shaped shell deformity (LSSD) on the posterior shell edge is known exclusively in wild mytilid mussels infected with photosynthetic Coccomyxa-like algae. LSSD forms due to the appearance of extra shell material; it only occurs if the mussel is heavily infected with the alga. Traditionally, observation of high amount of the green spots (algal colonies) on a large area of host soft tissues (most of the mantle and in adductor muscle) has been used to indicate a high infection rate. We examined 300 Mytilus spp. (100 small, 20-30 mm; 200 large, 40-60 mm) with a high degree of LSSD (parameter "d" > 5 mm) from the Lower St. Lawrence Estuary (Quebec, Canada). Green spots were absent in two large mussels, and were only present along the mantle posterior edge in 14 large mussels; other individuals had high infection levels. Our observations suggest that some individuals could be in a state of remission, or, even more optimistically - mussels may be able to resist the pathogen. LSSD is the stable through-time marker for detection of mytilid mussels that are or were infected with Coccomyxa algae, and, thus, may provide information for the study of mussel immunity and control of alga distribution/migration in coastal waters worldwide.

Since the early 1980s, attempts to develop a method for the retrospective estimation of water chemistry have been increasingly discussed in terms of bivalve sclerochronology. Although the problem with the interpretation of chemical data from shell growth patterns remains unsolved and a method, or at least its concept, has never been proposed, the optimism about the potential of the bivalve shell as a possible tool in retrospective environmental monitoring has reached the apogee nowadays. Here, we provide a review of the changes in the conceptual framework of the bivalve sclerochronology during more than thirty-five years of studies in the field, together with the analysis of the meaning of the key term 'sclerochronology'. The new term, 'sclerochronochemistry' (skleros - hard, chronos - time, and chemistry), is proposed in order to fill a gap between sclerochronology and sclerochemistry.

The posterior shell edge (PSE) of wild mytilid mussels that are highly infected with unicellular photosynthetic green algae Coccomyxa sp. exhibits an extra shell material (ESM). A recently proposed mechanism of ESM formation shows similarity with light-enhanced calcification (LEC), i.e., algae photosynthesis mediates low respiratory CO2 level in shell calcification site (PSE) to promote ESM precipitation. The present study evaluates if infection with algae may affect the δ13C content and metabolic carbon (CM) contribution to shells (PSE) in mussels from the Lower St. Lawrence Estuary, Québec, Canada. Environmental conditions may influence shell δ13C records. To underline possible algae photosynthesis effects, mantle, adductor muscle and shell δ13C are analyzed in infected and non-infected mussels collected from two sites with different salinities, seawater dissolved inorganic carbon (DIC) content, and hydrodynamic regimes. Shell δ13C and tissue δ13C correlate with seawater DIC and salinity. Shell δ13C values are lowest in non-infected mussels, whereas tissues δ13C values show the opposite relationship; in both cases, differences between δ13C values in non-infected and infected mussels are about 0.5‰. The percentage of CM incorporated into shell is higher (ca. 18%) for non-infected mussels than infected mussels (ca. 15%). Literature on the subject suggests that increased δ13C content and decreased %CM in shells of infected mussels must be related to algal photosynthetic activity. Our findings show that shell δ13C records permit the interpretation of ESM formation via LEC.

This report proposes a conceptual model for the formation of L-shaped shell deformity in wild mytilid mussels Mytilus spp. highly infested by unicellular photosynthetic microalgae Coccomyxa sp. where a key role plays the influence of the alga's photosynthesis on the parameters of carbonate system at the site of calcification. A number of research questions are posed, to be investigated through a combination of experimental methods.

During summer 2014-2017, wild mytilid mussels, highly infested with the pathogenic Coccomyxa-like microalgae, were collected along the Estuary and northwestern part of Gulf of St. Lawrence (Québec, Canada). Molecular identification showed that algae can be assigned to a single taxon, Coccomyxa sp. (KJ372210), whereas hosts are represented by Mytilus edulis, M. trossulus and hybrid between these two species. This is the first record of M. trossulus and hybrid among hosts of this pathogenic alga. Our results are indicative of a possible widespread distribution of Coccomyxa sp. in the Lower St. Lawrence Estuary and along coastal waters of Canadian Maritime provinces.

During autumn 2012 and spring 2013, blue mussels Mytilus edulis (L.) with strongly deformed (L-shaped) posterior shell margins and green spots in soft tissue (microalgae) were collected from intertidal zone along the south shore of the Lower St. Lawrence Estuary near Rimouski (Quebec, Canada). Identification of algal cells infesting mussels as Coccomyxa sp. was confirmed by rRNA sequencing and HPLC pigment analysis. Flow cytometric analysis revealed the presence of algal cells in the hemolymph and extrapallial fluid in mussels with deformed and non-deformed shells; concentrations of algal cells were ranged from about 200 mL(-1) in mussels with actually non-deformed shells to concentrations reaching up to 3.8 x 10(7) mL(-1) in mussels with heavily deformed ones. Chemical analyses of soft tissues led us to conclude that butyltin compounds and trace metals cannot be considered among factors responsible for the shell deformity observed. Using scanning electron microscopy, the biogenic nature of the erosion on the external shell surface and aragonitic lenses of prisms in the curvature zone of deformed shells (in sections) were recorded. The sequence of the green algae from M. edulis of the Lower St. Lawrence Estuary was closely related to Coccomyxa sp. infecting M. edulis from the Flensburg Fjord (North Sea) and Modiolus modiolus (L.) from the Vityaz Bay (Sea of Japan). (C) 2014 Elsevier Inc. All rights reserved.

Contemporary environmental challenges have emphasized the need to critically assess the use of bivalve mollusks in chemical monitoring (identification and quantification of pollutants) and biomonitoring (estimation of environmental quality). Many authors, however, have considered these approaches within a single context, i.e., as a means of chemical (e.g. metal) monitoring. Bivalves are able to accumulate substantial amounts of metals from ambient water, but evidence for the drastic effects of accumulated metals (e.g. as a TBT-induced shell deformation and imposex) on the health of bivalves has not been documented. Metal bioaccumulation is a key tool in biomonitoring; bioavailability, bioaccumulation, and toxicity of various metals in relation to bivalves are described in some detail including the development of biodynamic metal bioaccumulation model. Measuring metal in the whole-body or the tissue of bivalves themselves does not accurately represent true contamination levels in the environment; these data are critical for our understanding of contaminant trends at sampling sites. Only rarely has metal bioaccumulation been considered in combination with data on metal concentrations in parts of the ecosystem, observation of biomarkers and environmental parameters. Sclerochemistry is in its infancy and cannot be reliably used to provide insights into the pollution history recorded in shells. Alteration processes and mineral crystallization on the inner shell surface are presented here as a perspective tool for environmental studies.

A microstructural and mineralogical study shows the transition of aragonitic nacreous tablets to aragonitic prisms inside previously secreted nacre, i.e. without contact with the mantle or extrapallial fluid, in a field-collected mytilid bivalve Crenomytilus grayanus (D.). The intermediate zone between nacre and new prisms is represented by nacre tablets "stuck together" or by disordered calcium carbonate material. The modified nacre forms aragonitic lenses of prisms (ALPs). These lenses may reach 500 μm in thickness below the tunnels excavated by the shell borers. ALPs are similar to myostracal prisms in mineralogy, morphology, and orientation, but differ from those in the outer shell layer. The process of ALPs formation is different to that of normal shell formation (e.g. nacre-prisms transition between prismatic and nacreous layers), remote biomineralization, extra shell thickening, as well as, shell repair, erosion, deformation or disease. Response to shell excavation by boring organisms is discussed as the reason for the appearance of ALPs.

External shell surface (ESS) of bivalve mollusks is known to adsorb various metals dissolved in ambient water in high concentration. It is hypothesized here that the surface microtopography of the thin organic coating layer, periostracum, or calcareous shell (if periostracum was destroyed) plays a major role in the adsorption of actinides on ESS. Thorium (natural alpha-emitter) was used in short-term biosorption experiment with shell fragments of five bivalve mollusks. After a 72 h exposure to Th (∼6 kBq L−1), thorium concentration was measured on ESS using laser ablation inductively coupled plasma mass spectrometry; the distribution and density of alpha tracks were subsequently visualized by α-track autoradiography. A trend in reduced Th concentrations on the ESS was observed depending upon the species tested: (group 1 ∼4000 μg g−1) Chlamys islandica (M.), Mercenaria mercenaria (L.), Dreissena polymorpha (P.) > (group 2 ∼1200 μg g−1) Crassostrea virginica (G.) ≫ (group 3 ∼150 μg g−1) Mytilus edulis L. The microtopography of ESS was characterized by scanning electron microscopy revealing the high porosity of the calcareous surface of C. islandica and M. mercenaria, lamellate surface of periostracum in D. polymorpha, uneven but a weakly porous surface of periostracum of C. virginica, and a nearly smooth surface of the periostracum of M. edulis. This work has demonstrated, for the first time, the presence of a strong correlation between concentration of adsorbed Th and ESS microtopography, and the role of the periostracum in this process is discussed.

Until now only sinistral and scalariform deformations in gastropod shells were studied and typified. Other abnormalities have only been noted either as “shells with abnormalities”, “atypically developed shells”, “monsters” or “malformations”; the frequency of abnormal shells in a given population remained largely unknown. Here, shell abnormalities in seven species of pond snail of the Lymnaeidae were examined based on 25,000 adult individuals. Scalariformity, deformations of the aperture (two types), and “double” shell walls are recognized. Only large sample (> 100 shells collected together) have been considered for statistical purposes. The percentage of abnormal shells among the eurytopic species, viz. Lymnaea auricularia (Linnaeus, 1758), L. balthica (Linnaeus, 1758), and L. stagnalis (Linnaeus, 1758) ranged from 1.1% to 1.9%. Abnormalities were not found among species occupying a relatively narrow range of biotopes, viz. L. kazakensis Mozley, 1934, L. saridalensis Mozley, 1934, L. terebra (Westerlund, 1885) and L. atkaensis Dall, 1884. This observation suggests that shell abnormalities are most likely present in ecological generalists (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The classic ammonium carbonate vapor diffusion method (VDM) and the coprecipitation method (CM) in its modified form were applied for in vitro growth of calcium carbonate crystals on glass substrate and on calcitic and aragonitic shell layers of blue mussel Mytilus edulis (L.) and Iceland scallop Chlamys islandica (M.). The experiments were carried out using large volumes of growth medium (250ml and 1000ml). Crystallization using the VDM is relatively slow, but faster with the CM. The formation of calcium carbonate polymorphs is strongly influenced by the mineralogical phase in the uppermost layer of the shell substrate bathed in the experimental solution, even if magnesium ions are added to solution with the CM. The morphology of calcium carbonate crystals clearly differs between methods, and is influenced by the type of substrate. The effect of biomacromolecules released from the shell substrate on morphology and organization of calcium carbonate crystals is clearly observed with both methods of crystallization.

The enigmatic pentameride brachiopod Noetlingia Hall and Clarke, 1893 is revised and its stratigraphic range corrected. The type species Noetlingia tscheffkini occurs only within the upper Darriwilian (Ordovician) of the East Baltic and not in the Silurian as previously assumed. Thus, presently defined, the superfamily Porambonitoidea does not cross the boundary between the Ordovician and Silurian systems. Two other species occurring in the Lower to Middle Ordovician of South China and North America are assigned to Noetlingia.