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Cerastoderma edule and C. glaucum are two species of cockles that co-exist in European waters. They are morphologically similar but exhibit remarkable differences in biological, ecological, and genetic aspects, as well as in resistance to parasites (e.g., Martellia cochilia) and in disease incidence (e.g., disseminated neoplasia). Moreover, they differ in their economic significance; while C. edule represents a highly valuable marine resource, C. glaucum is only marginally fished. The aim of this work was to develop a simple and fast method that, for the first time, uses the sequence of a mitochondrial gene for the molecular differentiation of the two cockle species. A total of 304 partial sequences of the cytochrome c oxidase subunit I (COI) gene, retrieved from the Nucleotide database, were used to design two sets of species-specific primers to generate PCR products of different sizes (322 bp in C. glaucum and 247 bp in C. edule). The discriminatory ability of the PCR assay was tested in cockles from the Spanish, French, and Italian coasts with successful differentiation in all cases. This novel molecular identification method requires minimal technical equipment and can be carried out in one working day. For its simplicity, it can be very useful for conservation and sustainable management of the two cockle species, facilitating the assessment of distribution, abundance and relative sensitivity to viruses, parasites and diseases. [ABSTRACT FROM AUTHOR]

Cockles play a vital ecological role and provide valuable ecosystem services globally. However, the performance, production, and safe consumption of cockles are significantly influenced by their gut-associated bacteriome. Accurate understanding of gut-bacteriome interactions, and surveillance of pathogenic bacteria loads in cockles, rely on efficient DNA extraction methods that yield high-quality and representative bacterial DNA. Despite this importance, reliable extraction methods for cockles are currently overlooked. Therefore, we evaluated the performance of five DNA extraction kits (E.Z.N.A.® Soil DNA; FastDNA® Spin; DNeasy PowerSoil Pro; QIAamp PowerFecal DNA; ZymoBIOMICS™DNA Miniprep) in terms of DNA quality, yield, bacterial community structure (analysed by using denaturating gradient gel electrophoresis; DGGE), and bacteriome composition (analysed by 16S rRNA gene sequencing) in Cerastoderma edule gut. The DNeasy kit provided the highest purity and quantity of bacterial DNA, while the PowerFecal and Zymo kits exhibited reduced extraction efficiency. DGGE profiles revealed significant variability between the tested kits (R = 0.512; mean P = 0.011), but the FastDNA kit under-represented the bacterial community in cockles’ gut. Based on alpha diversity, the DNeasy kit outperformed the others and successfully detected all abundant genera found with the alternative kits. Our findings indicate that the DNeasy kit is an efficient DNA extraction method, enabling a molecular representation of the gut-associated bacteriome in C. edule. These results contribute to the development of effective techniques for studying the cockle gut bacteriome and its ecological implications.

Cancer is a multifaceted genetic disease characterized by the acquisition of several essential hallmarks. Notably, certain cancers exhibit horizontal transmissibility, observed across mammalian species and diverse bivalves, the latter referred to as hemic neoplasia. Within this complex landscape, epigenetic mechanisms such as histone modifications and cytosine methylation emerge as fundamental contributors to the pathogenesis of these transmissible cancers. Our study delves into the epigenetic landscape of Cerastoderma edule, focusing on whole-genome methylation and hydroxymethylation profiles in heathy specimens and transmissible neoplasias by means of Nanopore long-read sequencing. Our results unveiled a global hypomethylation in the neoplastic specimens compared to their healthy counterparts, emphasizing the role of DNA methylation in these tumorigenic processes. Furthermore, we verified that intragenic CpG methylation positively correlated with gene expression, emphasizing its role in modulating transcription in healthy and neoplastic cockles, as also highlighted by some up-methylated oncogenic genes. Hydroxymethylation levels were significantly more elevated in the neoplastic samples, particularly within satellites and complex repeats, likely related to structural functions. Additionally, our analysis also revealed distinct methylation and activity patterns in retrotransposons, providing additional insights into bivalve neoplastic processes. Altogether, these findings contribute to understanding the epigenetic dynamics of bivalve neoplasias and shed light on the roles of DNA methylation and hydroxymethylation in tumorigenesis. Understanding these epigenetic alterations holds promise for advancing our broader understanding of cancer epigenetics. [ABSTRACT FROM AUTHOR]

Multiple parasites can infect a single host, creating a dynamic environment where each parasite must compete over host resources. Such interactions can cause greater harm to the host than single infections and can also have negative consequences for the parasites themselves. In their first intermediate hosts, trematodes multiply asexually and can eventually reach up to 20% of the host's biomass. In most species, it is unclear whether this biomass results from a single infection or co-infection by 2 or more infective stages (miracidia), the latter being more likely a priori in areas where prevalence of infection is high. Using as model system the trematode Bucephalus minimus and its first intermediate host cockles, we examined the genetic diversity of the cytochrome c oxidase subunit I region in B. minimus from 3 distinct geographical areas and performed a phylogeographic study of B. minimus populations along the Northeast Atlantic coast. Within localities, the high genetic variability found across trematodes infecting different individual cockles, compared to the absence of variability within the same host, suggests that infections could be generally originating from a single miracidium. On a large spatial scale, we uncovered significant population structure of B. minimus, specifically between the north and south of Bay of Biscay. Although other explanations are possible, we suggest this pattern may be driven by the population structure of the final host.

Marine bivalves provide an important seafood resource, but conflicts between bivalve fisheries and conservation goals may arise.A scientific debate about cockle dredging in the Dutch Wadden Sea resulted in an apparent consensus among scientists of a severe and long‐lasting impact of the mechanical fisheries, and the fisheries were banned.Specifically, two highly cited papers concluded that the fisheries caused a strong reduction in bivalve recruitment for a period of 8 years and that the fisheries led to the loss of red knots from the Dutch Wadden Sea and a decline of the European wintering population.Here, we show that these papers had severe shortcomings in terms of data selection and data analysis and we challenge their conclusions. [ABSTRACT FROM AUTHOR]

The reproductive performance knowledge of economically important bivalves is essential to establish better shellfishery management measures and aquaculture programs. The reproductive cycle, as well as the nutrient storage and utilization of two Portuguese Cerastoderma edule populations from Óbidos and Ria Formosa lagoons were characterized by evaluating gonadal development stages, gonadal and condition indexes, as well as glycogen and total lipid content, over several consecutive years. The relationship between reproduction and environmental parameters (sea surface temperature and chlorophyll a) was assessed. The reproductive cycle of both populations of C. edule followed a clear seasonal pattern. The onset of gametogenesis took place in early autumn for both populations, and its evolution coincided with a temperature decrease which progressed throughout the winter. The mature stage was reached in spring, followed by a spawning period during spring and summer, triggered by a rise in temperature. After spawning, both populations progressed to a prolonged inactive stage. The condition index reflected the accumulation and utilization of glycogen, which was considerably higher in the Óbidos population. However, no relationships were found in the reproductive cycle of the species. Total lipids remained similar not only during the gametogenesis period, but also during the spawning period, which may be related to successive and simultaneous gamete production and release. [ABSTRACT FROM AUTHOR]

Mussels have great annual production in the world and their shells are discarded as a waste. Shells are calcium and carbon accumulators and, formed as a consequence of calcium carbonate biomineralisation. They can be used as bio-based composite materials in different fields. Hence, assessment of the chemical compound content and microstructure of shells is important for the prospective utility. For these reasons, structure of Cerastoderma edule, Chamelea gallina, Donax trunculus, Ruditapes decussatus shells were analyzed with X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS). In addition, microhardness was measured in shells. Our results indicated that shells have a flake like structure with irregular grains appearance morphologically at micrometric scale. The fractions of aragonite in particular shells were assessed. EDS analysis showed that Ca, C and O were major elements of C. edule, C. gallina, D. trunculus, R. decussatus in accordance with XRD data. The lowest microhardness (2.68±0.16 GPa) was in D. trunculus while the highest microhardness (4.28±0.32 GPa) was in C. edule. [ABSTRACT FROM AUTHOR]

The common cockle Cerastoderma edule is a widespread bivalve species inhabiting estuarine systems across the North East Atlantic, where it provides several ecosystem services, and represents a valuable fishery resource for local economies. However, anthropogenic pressure and more frequent extreme weather events threaten the resilience of the species. Spatially explicit information on species distribution is critical for the implementation of management and conservation practices. This study assessed the potential distribution of C. edule in the Ria de Aveiro by estimating the habitat suitability using an ensemble approach based on ecological niche modeling and recently developed hydrodynamic and water quality models to forecast both average and projected estuarine conditions. The models were developed for the summer of 2013 and spring of 2019 and potential range shifts in the species distribution were forecasted under projected environmental conditions: high and low estimates of freshwater discharge, a 2 °C increase in water temperature, and the combined effect of low freshwater discharge and increased water temperature. The results suggest that salinity, time of submersion, and current velocity play an important role in the distribution of cockles, and large areas were consistently classified with high habitat suitability. Increased freshwater discharge (both seasons) and low discharge coupled to increased temperature (spring) resulted in large decreases in suitable habitat. Conversely, low freshwater discharges and average (unchanged) temperatures increased the suitable habitat in the outermost regions of the Ria. The spatially explicit information provided contributes to a better understanding of the vulnerability of C. edule in the Ria de Aveiro to extreme weather events (e.g., droughts, river floods) and may support adaptive management strategies of the cockle fishery during these conditions. Moreover, this approach can be transferred to other estuarine ecosystems for which data describing the environmental conditions (e.g., derived from numerical models), and information about species presence are available (including data-poor species). [ABSTRACT FROM AUTHOR]

[Display omitted] • Cockle biomass was monitored for 15 years as a second intermediate host of trematodes. • Parasite abundance in cockles is correlated to cockle biomass with an 8 year time-lag. • Parasite/host systems can sustain a durable second intermediate host deficit. Infection by parasites with complex life cycles such as trematodes depends on many environmental factors which may result in a time-lag between host biomass fluctuations and parasite density in hosts. A cockle (marine bivalve, second intermediate host) population and its associated parasite community were monitored over 15 years. A time-shift correlation analysis suggests that trematode abundance in cockles responds to cockle biomass after a long delay (8 year time-lag). Thus, these parasites can sustainably support a deficit of their intermediate host. [ABSTRACT FROM AUTHOR]

Abstract Coastal systems provide many cultural ecosystem services (CES) to humans. Fewer studies have focused solely on CES, while those comparing CES across countries are even rarer. In the case of shellfish, considerable ecosystem services focus has been placed on nutrient remediation, with relatively little on the cultural services provided, despite strong historical, cultural, social and economic links between shellfish and coastal communities. The ecosystem services provided by the common cockle, Cerastoderma edule, have recently been described, yet the cultural benefits from cockles remain mostly unknown. Here, we documented the CES provided by C. edule in five maritime countries along the Atlantic coast of western Europe, classifying evidenced examples of services into an a priori framework. The high‐level classes, adapted from the Millennium Assessment and the Common International Classification of Ecosystem Services, were: inspirational, sense of place, spiritual & religious, aesthetic, recreation & ecotourism, cultural heritage and educational. A further 19 sub‐classes were defined. We followed a narrative approach to draw out commonalities and differences among countries using a semi‐quantitative analysis. Examples of CES provided by cockles were found for all classes in most countries. Cockles supply important and diverse cultural benefits to humans across Atlantic Europe, making it an ideal model species to study CES in coastal areas. Most examples were in cultural heritage, highlighting the importance of this class in comparison with classes which typically receive more attention in the literature like recreation or aesthetics. We also found that the cultural associations with cockles differed among countries, including between neighbouring countries that share a strong maritime heritage. The extent to which cultural associations were linked with the present or past also differed among countries, with stronger association with the present in southern countries and with the past in the north. Understanding the wider benefits of cockles could deepen the recognition of this important coastal resource, and contribute to promoting sustainable management practices, through greater engagement with local communities. This study is an important step towards better integration of CES in coastal environments and could be used as a framework to study the CES of other species or ecosystems. A free Plain Language Summary can be found within the Supporting Information of this article.

Transmissible cancers are a rare phenomenon in which cancer cells are passed between individuals, leading to the development of neoplasia in the host organism. Transmissible cancers have been identified in three independent clonal lineages in mammals and eight different clonal lineages in bivalves. This study focused on the development of a multiplex PCR assay for the detection of two types of bivalve transmissible neoplasias (BTN) of cockles Cerastoderma edule (CedBTN1 and CedBTN2). The diagnostic sensitivity (Se) and specificity (Sp) of the new PCR of hemolymph samples were assessed using a maximum likelihood estimation in the 88 samples compared to diagnoses obtained by histology and confirmed with genomic analyses. The results showed a Se of 100 % and a Sp of 98.1 % for CedBTN1, and a Se and Sp of 100 % for CedBTN2. The analytical Sp and Se were tested using DNA extractions from infected and non-infected C. edule and other bivalves affected by BTN. The assay demonstrated high analytical sensitivity and specificity, detecting down to 0.4 % of circulating CedBTN1 cells at a DNA concentration of 0.05 ng/µL in a hemolymph sample of a cockle with 85.7 % of CedBTN1 cells. The multiplex PCR assay was type-specific for CedBTN and capable of detecting both lineages simultaneously. Overall, this multiplex PCR assay is a reliable tool for the detection of transmissible cancers in cockles which will facilitate the diagnosis and monitoring of the disease., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The reproductive performance knowledge of economically important bivalves is essential to establish better shellfishery management measures and aquaculture programs. The reproductive cycle, as well as the nutrient storage and utilization of two Portuguese Cerastoderma edule populations from Óbidos and Ria Formosa lagoons were characterized by evaluating gonadal development stages, gonadal and condition indexes, as well as glycogen and total lipid content, over several consecutive years. The relationship between reproduction and environmental parameters (sea surface temperature and chlorophyll a) was assessed. The reproductive cycle of both populations of C. edule followed a clear seasonal pattern. The onset of gametogenesis took place in early autumn for both populations, and its evolution coincided with a temperature decrease which progressed throughout the winter. The mature stage was reached in spring, followed by a spawning period during spring and summer, triggered by a rise in temperature. After spawning, both populations progressed to a prolonged inactive stage. The condition index reflected the accumulation and utilization of glycogen, which was considerably higher in the Óbidos population. However, no relationships were found in the reproductive cycle of the species. Total lipids remained similar not only during the gametogenesis period, but also during the spawning period, which may be related to successive and simultaneous gamete production and release.

Coastal ecosystems are threatened by growing pressures related to global change. The evaluation of an ecosystem’s biodiversity and status is by consequence of increasing importance to assess potentially undergone changes and predict their future trajectory for management and conservancy purposes. Biotic indicators sensitive to ecosystem changes are thus continuously sought for. Trematode parasite communities were examined as potential indicators of environmental changes, considering that the achievement of their complex life cycle is modulated by several factors. Indeed, the rule for trematode is that each species complete their cycle by a succession of three different host species and two free-living stages, thus depending on several biotic and abiotic factors. To this end, we examined the trematode community infecting the common cockle in Banc d’Arguin, Arcachon Bay, France. Monthly data extending over 16 years and sampled at a single station were compared to field book notes describing the changes of the closely surrounding landscape. In 2021, we also sampled cockles at 15 stations presenting different substrate features along the bank. Over time, seven out of nine changes of the trematode community structure presented concordances with changes in landscape. We hypothesize this was related to the environment heterogeneous substrate (i.e., temporal succession of oyster parks, bare sands and seagrass) with cascading effects on host populations. However, some changes could not solely be explained by changes in landscape. Our spatial study showed that the trematode communities exhibited intricate infection patterns with a complex interaction between substrate heterogeneity and larval dispersal ability of parasites. Thus, trematode communities might be potential indicators of subtle changes in the environment. However, it remains unclear which scale of environmental changes trematodes are actually sensitive to.

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Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The distribution of the common cockle Cerastoderma edule was studied in Levrier Bay, Mauritania, at the southern margin of its range. The populations of the common cockle in Levrier Bay are located in the littoral zone of two closed bays, both with minimum surf and a reduced tidal influence. Mainly sandy and, to a lesser extent, sandy-silt grounds serve as habitats. The morphological peculiarities, the size–weight structure, abundance, and biomass of the common cockle populations were studied, analyzed, and compared for areas of commercial harvesting of this mollusk and in pristine areas. The abundance and biomass of benthic organisms accompanying the common cockle are also presented. [ABSTRACT FROM AUTHOR]

Germany is an EU member state and is thus obliged to monitor and protect its marine and coastal areas in the context of international treaties (e.g. EU Marine Strategy Framework Directive, EU Natura2000 directives, Trilateral Monitoring and Assessment Programme, OSPAR) to achieve the good environmental status (GES). Suitable indicators thus need to be developed to assess the status of relevant ecosystems. Intertidal bivalve beds belong to the most productive habitats in the shallow coastal waters of the Wadden Sea but are highly dynamic and difficult to monitor. Extensive benthos and sediment sampling are required to study their development and distribution. We therefore evaluated the suitability of herring gulls (Larus argentatus) as a bioindicator species for monitoring these habitats. As flexible and opportunistic top-predators, herring gulls prefer to forage on intertidal flats and feed on bivalves (Cerastoderma edule, Mytilus edulis, Ensis leei) and crustaceans, with intertidal habitats near the breeding colony preferred during the incubation period. We used state of the art tracking devices to analyse habitat selection by herring gulls, and assessed how this was driven by biotic and abiotic factors. We then designed a habitat model to predict the occurrence of intertidal bivalve beds for directed monitoring, based on GPS logger data from herring gulls and hydrodynamic data. Both methods showed high correlations of herring gull foraging patterns with bivalve biomass and inundation time, depending on the distance from the breeding colony. The movement patterns of herring gulls clearly mirrored intertidal bivalve distributions. These results showed that combining GPS-logger data for top-predators, such as birds, with environmental data has great potential for monitoring and assessing the GES. We propose that herring gulls may be used as an indicator to locate bivalve beds in the Wadden Sea and to detect changes in the food web.

Studies on marine community structure and their modulation by horizontal and vertical abiotic gradients have focused on free-living species, neglecting parasites despite their important role in ecosystems. Field observations, a laboratory flume experiment and modelling were used to examine parasite infection patterns related to host tidal and spatial position along a Portuguese coastal lagoon (Ria de Aveiro). Cockles (Cerastoderma edule) and trematodes were used as a host-parasite model to test the hypotheses: (1) higher infection levels in subtidal cockles, positioned downstream and (2) higher current velocity in downstream areas with consequent higher cockle infection. Cockles were collected from two spatial and tidal positions in two seasons. The relationship between current velocity and cockle infection was examined experimentally by exposing cockles to cercariae of Himasthla elongata at two current velocities. Intertidal cockles displayed higher infection, highlighting vertical position as an important driver of infection possibly due to first host proximity and/or trematode life cycle facilitation (higher cockle exposure to final host predation). The hydrodynamic model showed that the Ria de Aveiro was abiotically heterogenous with cockles displaying higher infection levels in the downstream area. Multiple regression analysis demonstrated a positive correlation between salinity, dissolved oxygen, current velocity and trematode abundance. The influence of current velocity on infection success was corroborated experimentally. The present study demonstrated the importance of host vertical and horizontal position on trematode infection, highlighting the positive influence of current velocity by supporting settlement and promoting favourable abiotic conditions. [ABSTRACT FROM AUTHOR]

Abstract The cockle Cerastoderma edule was exposed to four concentrations (5, 10, 20 and 70 μg L-1) of carbamazepine (CBZ). This anticonvulsant was found to alter the mussel behavior of by reducing its clearance rate (CR). Analysis of CBZ accumulation in tissues of C. edule was carried out using HPLC-UV after 48 or 96 hours of exposure. In addition, an overproduction of H2O2 by the bivalves was detected following exposure to CBZ but nitrite levels remained unchanged. Moreover, superoxide dismutase and catalase activities showed a significant increase in relation to their contact with CBZ. The activity of the biotransformation enzyme gluthatione-S-transferase did not change during exposure. Malondialdehyde (MDA) levels indicating cellular damage, increased when bivalves were exposed to 20 and 70 μg l-1 of carbamazepine for 96 h CBZ. The results also indicate that acetylcholinesterase activity (AChE) was inhibited in all CBZ concentrations during the 48 h exposure period. However, during the 96 h exposure period, AChE was only inhibited at the highest concentration. Further studies are needed now for more exploration of the toxicity of CBZ since it could be bioaccumulable throughout the food web and may affect non-target organisms.

Accelerator mass spectrometry (AMS) radiocarbon (14C) dating of Cerastoderma edule (Linnaeus 1767) and Mytilus edulis (Linnaeus 1758) shells sampled in AD 1889 near the island of Wangerooge gave a new local correction factor ΔR of −85 ± 17 14C years for the Wadden Sea area. The value is considerably higher than the available scattered data from the North Sea, which were obtained from pre-bomb growth rings of living Arctica islandica (Linnaeus 1767). This can be explained by the incorporation of 14C-depleted terrestrial carbon into the shell material which compensates the intensified exchange of CO2 between atmosphere and shallow coastal water, e.g. by tidal currents. Additionally, two examples of application of the new ΔR value in coastal research give deeper insights into the dynamics of bivalve shell preservation in the Wadden Sea and the need for further research to clarify the Holocene reintroduction of Mya arenaria (Linnaeus 1758) into European waters. [ABSTRACT FROM AUTHOR]

Background: The common cockle Cerastoderma edule plays an important ecological role in the marine ecosystem both as an infaunal engineer (reef forming and bioturbation) and a food source for protected bird species in its European range. Cockle beds are found in close proximity to aquaculture and fisheries operations, which can be "hot spots" for infectious agents including viruses and bacteria. Ostreid herpesvirus-1 microVar (OsHV-1 μVar) has spread to many Pacific oyster Crassostrea gigas culture sites globally, where it has been associated with significant mortalities in this cultured bivalve. Knowledge on the impact of the virus on the wider ecosystem, is limited. As the likelihood of released virus dispersing into the wider aquatic ecosystem is high, the plasticity of the virus and the susceptibility of C. edule to act as hosts or carriers is unknown. Methods: In this study, wild C. edule were sampled biweekly at two C. gigas culture sites over a four-month period during the summer when OsHV-1 μVar prevalence is at its highest in oysters. C. edule were screened for the virus molecularly (PCR, qPCR and Sanger sequencing) and visually (in situ hybridisation (ISH)). The cockle's ability to act as a carrier and transmit OsHV-1 μVar to the oyster host at a temperature of 14 ℃, when the virus is considered to be dormant until water temperatures exceed 16 ℃, was also assessed in laboratory transmission trials. Results: The results demonstrated that OsHV-1 μVar was detected in all C. edule size/age cohorts, at both culture sites. In the laboratory, viral transmission was effected from cockles to naïve oysters for the first time, five days post-exposure. The laboratory study also demonstrated that OsHV-1 μVar was active and was successfully transmitted from the C. edule at lower temperatures. Conclusions: This study demonstrates that OsHV-1 μVar has the plasticity to infect the keystone species C. edule and highlights the possible trophic transmission of the virus from cockles to their mobile top predators. This scenario would have important implications, as a greater geographical range expansion of this significant pathogen via migratory bird species may have an impact on other species that reside in bird habitats most of which are special areas of conservation. [ABSTRACT FROM AUTHOR]

The decline of natural populations of the common cockle (Cerastoderma edule) through the European coast is posing a threat to local small-scale fisheries. These declines are primarily attributed to the prevalence of several pathogens and the disseminated neoplasia in cockle populations. The institution of a biobank of cryopreserved larvae could enhance hatchery production and help the restocking. The present work aimed at the development of a cryopreservation protocol for larvae of the common cockle using the mollusk cryopreservation protocols designed in our laboratory. Toxicity bioassays and short-term cryopreservation experiments were performed for protocol optimization according with cellular tolerance. Once settled, the viability of cryopreserved larvae was studied long term. Toxicity tests evidenced high tolerance of larvae against detrimental effects of Cryoprotecting Agents (CPAs). Cryopreservation of 48 h-old D-larva showed a 100% survival when increasing the equilibrium time from 15 to 60 min and using Propylene-Glycol (PG) + 0.4 M Trehalose (TRE) in Filtered Sea Water (FSW) and 60 min of exposure to CPA solution before slow-cooling. However, when cryopreserving the older larvae, the variation in equilibrium times hardly showed any effect but 10% Ethylene-Glycol (EG) + 0.4 M TRE and 60 min of exposure yielded the best relative survivorship (100%). Cryopreservation caused a significant delay on the growth rate of the latest larval stage. However, cryopreserved larvae survived to day 4–6, while 30 ± 12.17% of control larvae developed into pediveliger stage, of which 50% settled and transformed into juvenile cockles. These results demonstrated the role of the cell-type specificity in cryopreservation and highlight the importance of studying potential long-term effects of this tool to ensure the viability of the protocols. [ABSTRACT FROM AUTHOR]

Trematode parasites are distributed worldwide and can severely impact host populations. However, their influence on ecosystem functioning through the alteration of host engineering behaviours remains largely unexplored. This study focuses on a common host parasite system in marine coastal environments, i.e., the trematode Himasthla elongata, infecting the edible cockle Cerastoderma edule as second intermediate host. A laboratory experiment was conducted to investigate the indirect effects of metacercarial infection on sediment bioturbation and biogeochemical fluxes at the sediment water interface. Our results revealed that, despite high parasite intensity, the sediment reworking and bioirrigation rates, as well as nutrient fluxes, were not impacted. This finding was unexpected since previous studies showed that metacercarial infection impairs the physiological condition of cockles and induces a mechanical obstruction of their feet, thus altering their burrowing capacity. There are several explanations for such contrasting results. Firstly, the alteration of cockle behavior could arise over a longer time period following parasite infection. Secondly, the modulation of cockle bioturbation by parasites could be more pronounced in older specimens burying deeper. Thirdly, the intensity of the deleterious impacts of metacercariae could strongly vary across parasite species. Lastly, metacercarial infection alters cockle fitness through an interaction with other biotic and abiotic environmental stressors.

The recurrent emergence of infection outbreaks associated with shellfish consumption is of extreme importance for public health. The present study investigated the potential application of phages AH-1, AH-4, and AH-5 to inactivate Aeromonas hydrophila, a causative agent of infections in humans associated with bivalve shellfish consumption. The inactivation of A. hydrophila was assessed in vitro, using a liquid culture medium, and in vivo, using artificially contaminated cockles with A. hydrophila ATCC 7966. In the in vitro experiments, all phages were effective against A. hydrophila, but phage AH-1 (with a maximum reduction of 7.7 log colonies forming units CFU/mL) was more effective than phages AH-4 and AH-5 (with reductions of 4.9 and 4.5 log CFU/mL, respectively). The cocktails AH-1/AH-4, AH-1/AH-5, AH-4/AH-5, and AH-1/AH-4/AH-5 were slightly more effective than the single phage suspensions. The phages presented a low emergence rate of phage-resistant mutants. When artificially contaminated cockles were treated in static seawater with phage AH-1, around 44% of the added A. hydrophila (1.0 log CFU/g) was inactivated. The results of this study suggest that phage therapy can be an effective alternative to control human pathogenic bacteria during depuration.

Using mitochondrial COI sequencing, we explored the genetic diversity and population structuring of the common cockle Cerastoderma edule (Linnaeus, 1758) in the Norwegian and Barents Seas. Phylogeographic diversity and hence the evolutionary history of C. edule on the Scandinavian and Russian coastlines were found to be richer than expected for populations of temperate species in postglacially colonized seas. A major phylogeographic break at Lofoten Islands separated a group of subarctic populations dominated by a distinct star‐shaped clade of haplotypes from those to the south, extending to the North Sea and having highest gene diversities (h). At the northeastern edge of the range of C. edule, the Russian Murman coast, populations show a mosaic structure with considerable admixture of haplotypes from the south and high local‐scale variation in haplotype diversity (ranging between 0 and 0.8). To explain this mosaic we refer to the core‐satellite metapopulation model, with Norwegian populations as core, and Murman populations as satellites. Our results contradict the conventional biogeographic paradigm implying lack of metapopulation structuring in marine broadcast spawning invertebrates. Hypotheses considered to explain the origin of the unique variation in cockles from Northern Norway involve an early postglacial colonization and establishment of these populations (10–12 ka ago), a persistent oceanographic break at Lofoten, and a mitochondrial selective sweep associated with the postglacial recolonization of the subarctic seas by the boreal C. edule. Using mitochondrial COI sequencing, we revealed strong population structuring in the common cockle Cerastoderma edule (Linnaeus, 1758) populations from the Norwegian and Barents Seas. Low genetic diversity of the subarctic cockle populations predominantly consists of a distinct clade of haplotypes, which is much less common in populations located south of the Arctic Circle and completely lacking in the North Sea. The Barents Sea C. edule seems to be the first conclusive example of true metapopulation revealed in marine broadcast spawners. [ABSTRACT FROM AUTHOR]

The main goal of this monitoring program was to evaluate the contamination in the intertidal environment of Óbidos Lagoon by the metals Cd, Pb, and Ni on water, sediments, and on biological samples, using the bivalve Cerastoderma edule (common name: cockle) as a biomonitor. Since C. edule is an edible mollusc, the risk of their consumption by humans from this lagoon was also evaluated. The study was performed in a restricted area of the lagoon—the ML station—where human activities, such as shellfish harvesting, intersect with the natural processes occurring in this system. The results obtained revealed that the water samples were polluted with Cd and Pb with concentrations (0.00025 mg l−1 and 0.0072 mg l−1) above the maximum legislated on the Directive 2008/105/EC, while for Ni, this occurred only on one of the seasons sampled (summer 2010: 0.029 mg l−1). The sediments were not contaminated with Cd and Ni, and the contamination detected for the metal Pb, allowed the classification of this station as an unpolluted site ([Pbmin] = 7.477 mg.kg−1 and [Pbmax] = 19.875 mg.kg−1). On biological samples, comparing the results of metal contaminations with the values of the maximum levels fixed by European Commission Regulation (EC) No 1881/2006 and USFDA, all the results were below the legal value. Therefore, during the period of study, the consumption of this bivalve by humans was safe. Also, BAF and CF calculations suggest that C. edule can be used as a biomonitor to determine the source of the contaminations. This study supported the use of C. edule as a biomonitor to assess the contamination by the metals Pb and Ni at the Óbidos Lagoon and allowed to predict the potential transfer of metals to higher trophic levels with potential impacts on the natural and human communities. [ABSTRACT FROM AUTHOR]

Bivalves have proved to be useful bioindicators for environmental pollution. In the present study, mussels (Mytilus galloprovincialis), cockles (Cerastoderma edule), and razor shells (Solen marginatus) were collected in the Ebro Delta, an extensive area devoted to rice farming and affected by pesticide pollution, from April to July, the heaviest rice field treatment period. Possible effects of pollution were assessed through biochemical markers (carboxylesterase (CE), antioxidant and neurotoxicity-related enzymes, and lipid peroxidation levels). Data on environmental variables, bivalve reproductive condition, and presence of organic pollutants, marine phycotoxins, pathogens, or histopathological conditions in bivalve's tissues were also evaluated. Although the bioaccumulated pesticides did not explain the patterns observed for biochemical responses, the obtained results point to an effect of environmental pesticide pollution on enzymatic markers, with a prominent contribution of CE to such changes. Mussels and razor shells provided a more sensitive biochemical response to pollution than cockles. Environmental variables, bivalve reproductive condition, and marine phycotoxins did not seem to have a relevant effect on the biomarkers assessed. [ABSTRACT FROM AUTHOR]

Archaeological fieldwork at Hjarnø Sund in Horsens Fjord (eastern Jutland, Denmark) has explored an eroding Mesolithic shell midden. Its stratigraphy is characterized by two layers, containing marine mollusk taxa typically collected by Mesolithic hunter-gatherers for food. In the field, the lower layer appeared to be dominated by oysters (Ostrea edulis), while the upper one by cockles (Cerastoderma edule), which was confirmed by our zooarchaeological study. Accelerator mass spectrometry radiocarbon (AMS 14C) dating on shells and paired charcoal samples from the two layers indicate that these are chronologically consecutive (separated by as little as 0–163 yr [95.4%]) and that the oyster-to-cockle shift dated between ~5500–5300 and ~5300–5200 cal BC (around or just after the Kongemose/Ertebølle transition). The shell midden at Hjarnø Sund is, thus, one of the oldest-known in Denmark, demonstrating that intensive shellfish exploitation was a hallmark of the Ertebølle culture from its inception. Oyster-to-cockle shifts, thus, also occurred at times other than the Mesolithic–Neolithic Transition and may have been ultimately caused by local shoreline displacements, resulting from changes in sedimentation, possibly induced by drops in relative sea level. [ABSTRACT FROM AUTHOR]

As filter feeders, marine bivalves inhabiting estuarine and coastal areas are directly exposed to microplastics (MPs) in water. To assess whether MPs number, and their shape, size, colour, and polymer type present in mussels (Mytilus galloprovincialis) and cockles (Cerastoderma edule) varied over one year, bivalves were collected over the year of 2019 in the lower part of the coastal Aveiro lagoon, Portugal. After extraction from the bivalve's whole-body soft tissues, a subset of the visually inspected particles was randomly separated for identification using the Fourier-transform mid-infrared (FT-MIR) spectroscopy. A fraction of the inspected particles, 26–32% of particles >100 μm, and 59–100% of smaller ones were confirmed as MPs. Concentrations varied within the intervals of 0.77–4.3 items g−1 in mussels and 0.83–5.1 items g−1 in cockles, with the lowest values observed in January. In winter, the accumulation of large-sized fibers was composed of a mixture of plastic types, which contrasted against the most abundant MPs in summer consisting mainly of polyethylene of diverse size classes and shapes. Temperature decrease registered in winter might have triggered a lower filtration rate, resulting in lower MPs concentrations in the whole-soft body tissues of organisms. Different properties of MPs found in bivalves between January–February and August–September appear to reflect changes in the characteristics of MPs available in the Aveiro lagoon. [Display omitted] • 26–32% (>100 μm) and 59–100% (<100 μm) of the inspected particles confirmed as MPs. • MPs concentrations varied over one year seasonally; lowest values observed during winter. • Large-size fibers composed of a mixture of plastic types retained during winter. • Contrast in PE particles profile (diverse sizes and shapes) in warmer periods. [ABSTRACT FROM AUTHOR]

A huge, unprecedented mortality of cockle Cerastoderma edule caused by the protist Marteilia cochillia, which had never before been detected in Galicia (NW Spain), brought on a cockle fishery collapse in the Ría de Arousa (Galicia) in 2012. Since then, the disease dynamic pattern in the shellfish bed of Lombos do Ulla (at the inner area of that ria) involved an overwhelming annual wave of infections and subsequent cockle mass mortality that caused the near extinction of every cohort recruited to that bed. However, a pattern shift was detected among wild cohorts recruiting since 2016, with progressive declines of marteiliosis prevalence and increments in cockle survival. This suggested 2 non-exclusive hypotheses: increasing marteiliosis resistance through natural selection, and reduced abundance and/or virulence of the parasite. A field experiment was performed to assess these hypotheses by comparing marteiliosis prevalence and severity, as well as mortality, in cockles that naturally recruited to this bed in 2017 and 2018 with those of naïve cockles collected from a marteiliosis-free area and transplanted into Lombos do Ulla in 2017 and 2018. Marteiliosis prevalence and cumulative cockle mortality quickly reached very high values among the transplanted cockles, demonstrating that the parasite remained present and virulent in the area. Conversely, marteiliosis prevalence and cockle mortality were much lower in the cockles that recruited to Lombos do Ulla, suggesting increased resistance that may have been driven by natural selection. The young age at which cockles start reproduction and the very high mortality caused by marteiliosis may have enhanced natural selection.

Understanding possible effects of cockle dredging on bivalve dynamics should include studies of the influence of cockle abundance on bivalve recruitment and of effects of fishery on survival of recruits present at the time of fishing and on future recruitments. Numerical densities of adult cockles and of recruits of Cerastoderma edule, Limecola balthica and Mya arenaria were monitored by twice annual sampling for 21 years (1973–1993) along 7 transects in the fished part of Balgzand, a 50-km 2 tidal flat area in the westernmost part of the Wadden Sea. Between-year variability in recruitment success in all 3 species was negatively correlated with adult-cockle abundance. Recruit densities as estimated in August were relatively low in years of cockle fishing in all of these species. This was so already well before fishing started in September. So these low densities were not an effect of fishery, but of the high cockle abundance that made cockle dredging profitable. The proportions of recruit numbers estimated in August (just before cockle dredging) that were still present half a year after fishing (in March) were not different between fishing and non-fishing years nor between fished and unfished areas in fishing years. Densities of new recruits in years following cockle-dredging somewhere in the area were not different from densities in years not preceded by any fishery nor were they lower at the fished sites in the year after fishing than in other years. The lack of significant influences of fishery in the studied area and period was observed in all 3 bivalve species. The above results were obtained in areas with relatively muddy sediments. Earlier reported negative effects of cockle-dredging on bivalve recruitment may be limited to the minority of tidal flats characterized by relatively coarse sediments with <1% of silt. [ABSTRACT FROM AUTHOR]

Cerastoderma edule (edible cockle) is among the most exploited bivalves in Europe playing an important socio-economic role. Cockles live in estuaries and lagoons where their population is controlled by several environmental factors including parasitism. Parasites represent an important part of the world known biodiversity but are often neglected. Trematodes are the most prevalent macroparasites of cockles being able to exert an impact both at the individual and population levels. Therefore, it is of prime relevance to recognize and understand the parasite-host system dynamics in order to better predict potential conservation threats to bivalve populations and to maximize the success of stock and disease episodes management. Cockle monitoring was conducted in 2012 and 2016, in six and eight stations, respectively, at the Ria de Aveiro coastal lagoon, Portugal. Cockles were sampled in one single occasion in 2012 and seasonally in 2016. The tested hypothesis is that the trematode community in cockles was spatially and seasonally heterogeneous but stable over time. The main result showed that despite a relative homogeneity of the parasite community structure in cockles, the among-years heterogeneity of trematode communities was higher than among-stations and among-seasons heterogeneity rejecting the postulated hypothesis. Results demonstrated that trematode communities from the Ria de Aveiro are characterized by low abundance, which resulted in a spatial and seasonal trematode homogeneity (despite an overall channel difference and a slight downstream-upstream gradient). The interannual analysis showed a worrisome loss of trematode diversity and prevalence which consequently indicates an important loss of overall diversity and/or environmental conditions reflecting the negative effects of global change (mean temperature rise and overharvesting, among others). The present study highlighted the importance of trematodes in characterising their associated environment and respective biodiversity which might be helpful to assess ecosystem ecological status and to identify threatened areas. [ABSTRACT FROM AUTHOR]

As an approach to elucidating the “value” of detritus as a food source for bivalves, we analysed the capability of the common cockle ( Cerastoderma edule ) to modulate feeding and digestive rates during acclimation to low and high food rations of detrital diets with either low ( Juncus maritimus ) or high digestibility ( Enteromorpha spp.). On acclimation day 3, feeding rates were similar in cockles fed different detrita; however, the absorption rate was higher in cockles fed Enteromorpha spp. With J. maritimus , rising food rations promoted an exponential decrease in absorption efficiency, whereas with Enteromorpha spp., absorption efficiency was only marginally reduced. During acclimation, cockles improved the rate at which both detritus were assimilated by means of increasing ingestion rates while maintaining absorption efficiency. When the time-course of digestive carbohydrase activities was monitored during acclimation to either detritus or phytoplankton ( Isochrysis galbana ), we found that only phytoplankton promoted the induction of cellulase activity in the digestive glands of cockles. This response in cockles fed phytoplankton promoted an increase in the digestibility of Enteromorpha spp., but had no effect on the digestibility of J. maritimus . [ABSTRACT FROM AUTHOR]

Some pea crabs are parasite of bivalves and may cause a significant effect on the host's condition. In this study, the prevalence of the pea crab Afropinnotheres monodi and its effect on host condition are assessed for two commercially important bivalves (the mussel Mytilus galloprovincialis and the cockle Cerastoderma edule ) from three natural beds of the Gulf of Cadiz (SW of Iberian Peninsula). The average prevalence of A. monodi ranged from 4.0% (Bay of Cadiz) to 51.4% (Carreras River) for cockles and from 30.5% (Bay of Cadiz) to 45.4% (Carreras River) for mussels. For both hosts, most bivalves were infested by a single pea crab (96.0% of cockles and 92.4% of mussels); among multiple infestations, one male and one female was the dominant combination (72.7% of cockles and 77.8% of mussels). Infested mussels showed a significantly decreased condition index (14.7%, on average), whereas crab infestation did not significantly affect the condition index of cockles (2.2%, on average). When the wet weight of the pea crab represented >5% of the wet weight of the host, an average condition loss of 12.7% and 15.9% were observed for cockles and mussels, respectively. As the relative condition loss of both mussels and cockles was negatively correlated with the relative size of the pea crab, the mentioned interspecific differences in the pea crab effects may be mainly due to the higher prevalence of soft females (larger size and obligatory parasitism) in mussels (70.6%, on average) and of hard females and males (smaller size and facultative parasitism) in cockles (81.1%, on average). This study highlights the importance of knowing the life cycle and host use of the pea crab A. monodi to ascertain the possible negative effect of this parasite on mussel farms and exploited cockle beds. [ABSTRACT FROM AUTHOR]

At the past 30 years were recorded an intensive practice in the use of fertilizers and pesticides, mainly in the European Mediterranean region, that, in particular cases, exceeded the limits of regular legislations established by the European Union. The widespread use of these chemicals compounds and the pressure over agricultural fields near valuable ecologically coastal areas conducted to the implementation of monitoring plans to the recovering of aquatic ecosystems. Since the 80′s Mondego estuary (Figueira da Foz, Portugal) has been harassed by anthropogenic pressures, which triggered the implementation of mitigation monitoring programs at the last 18 years, allowing its recovery. Copper sulphate is used in industrial activities, but also it is much used in pesticides formulations, with application in agricultural activities, namely in rice farms to control pests. Studies reported that copper may affect biochemical processes, such lipid metabolism of some organisms, although specific changes in fatty acid (FA) profiles are still unknown. Nowadays, bivalve species are used in ecotoxicological bioassays due some particular characteristics, such as the wide distribution, ecological relevance, the capacity to filter and ingest large volumes of sediment particles and water and ease handling in the field and in the laboratory. Therefore, this work aims to determine toxic effects and changes in fatty acids profile composition of the two marine bivalve species Cerastoderma edule and Scrobicularia plana when exposed to copper sulphate, considering small (medium body size = 1.97 cm and 3.47 cm, respectively) and big (medium body size = 2.45 cm and 4.20 cm, respectively) size classes. In a first phase organisms were exposed under laboratorial conditions to copper sulphate to determine lethal concentration; at a second phase, it was compared the FA profile and the nutritive quality of both species and size classes at the field and in the lab. Our results state C. edule is more sensitive to copper sulphate (LC 50 = 0.818 (0.595–0.987) mg/L; 1.129 (0.968–1.289) mg/L, to big and small organisms, respectively) than S. plana (LC 50 = 2.563 (2.229–2.903) mg/L; 4.705 (3.540–12.292) mg/L, to big and small organisms, respectively). Furthermore the last one presents greater abundance and variety of FA and essential fatty acids (EFA), namely DHA and EPA, rates than C. edule . Still, big size class of both bivalve species is the most affected by the contaminant. [ABSTRACT FROM AUTHOR]

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia ( NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni- and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae-like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae-like parasites infecting molluscs outside the United States is confirmed. [ABSTRACT FROM AUTHOR]