Bivalve mollusks from the Kurasiyskaya Formation in the Southwest Sakhalin

In the UK several quantitative methods exist for the examination of bivalve molluscan shellfish for sewage contamination. These methods include roll tubes, pour plates and most probable number (MPN) techniques, but there is no national standard method. A comparative study was made of the most commonly used methods for detection of Escherichia coli in bivalve shellfish. Schemes employing solid media, such as the roll tube and pour plate methods, underestimated faecal contamination in shellfish tissue compared with a liquid MPN multiple test-tube method using minerals-modified-glutamate broth (MMGB) as primary enrichment medium. The composition of MMGB apparently permits repair of sublethally injured cells of E. coli. Incorporation of resuscitation stages into the pour plate technique did not yield higher counts. A standardized MPN technique for examination of bivalve molluscan shellfish for E. coli content is proposed as a possible national reference procedure pending further collaborative assessment.

IntroductionShellfish play an important role in ecological restoration and as carbon (C) sinks, but studies on their ecological carrying capacity (ECC) and C sequestration potential are sparse.MethodsIn this study, we selected a 57-hectare artificial oyster reef in a typical marine ranching in Bohai Bay, China, to evaluate the ECC and their C sequestration potential of bivalve shellfish, and projecting their impact on functional groups in the system, with an Ecopath with Ecosim (EwE) food web model. We conducted four biological surveys to obtain the biomass measurements, with one conducted in each of the summer, autumn, and winter of 2019 and one in the spring of 2020; and the functional groups included in the surveys comprised fish, cephalopods, crustaceans, snails, bivalve shellfish, annelids, other macrobenthos, meiobenthos, starfish, sea cucumbers, zooplankton, phytoplankton, and detritus.Results and DiscussionThe EwE model prediction results showed that the ECC of bivalve shellfish was established to be 282.66 t/km2, far more than the existing quantity of 187.76 t/km2. Therefore, at present, the ecosystem of the study marine ranching is not yet mature. Moreover, our ecological network analysis parameters indicated that the marine ranching ecosystem will be mature and stable when the bivalve shellfish population reaches its ECC. However, the increase in bivalve shellfish biomass will result in a decrease in the population sizes of species competing for food resources with bivalve shellfish, mainly gobiid fish such as Tridentiger bifasciatus, Tridentiger trigonocephalus, Tridentiger barbatus. Simultaneously, when the bivalve shellfish reach their ECC, 29.23 t of CO2 can be sequestrated by bivalve shellfish, comprising 14.32 t being removed from the ecosystem as prey and 14.91 t being stored on the seafloor through biodeposition.ConclusionTherefore, the research demonstrated that, within the scope of ECC, the increasing bivalve shellfish can improve the C sequestration capacity of the marine ranch ecosystem, and effective management of bivalve shellfish in marine ranching can improve the economic benefits and C sink service functions of marine ranching.

Hepatitis E virus genotype 3 in shellfish, United Kingdom.

Human norovirus (HuNoV) is a major foodborne pathogen that causes acute viral gastroenteritis, and bivalve shellfish are one of the main carriers of HuNoV transmission. A comprehensive understanding of bivalve shellfish-related HuNoV outbreaks focusing on contamination factors, bioaccumulation mechanisms, and pre- and post-harvest interventions is essential for the development of effective strategies to prevent contamination of shellfish. This review comprehensively surveys the current knowledge on global contamination and non-thermal treatment of HuNoV in bivalve shellfish. HuNoV contamination in bivalve shellfish is significantly related to the season and water. While evaluating the water quality of shellfish-inhabited waters is a key intervention, the development of non-heat treatment technology to effectively inactivate the HuNoV in bivalve shellfish while maintaining the flavor and nutrition of the shellfish is also an important direction for further research. Additionally, this review explores the bioaccumulation mechanisms of HuNoV in bivalve shellfish, especially the mechanism underlying the binding of histo-blood group antigen-like molecules and HuNoV. The detection methods for infectious HuNoV are also discussed. The establishment of effective methods to rapidly detect infectious HuNoV and development of biological components to inactivate or prevent HuNoV contamination in shellfish also need to be studied further.

Bivalve shellfish is a delicious and healthy diet in coastal cities around the world. They are important food items in several dietary regimes in the Niger delta. This study investigated consumers’ perceptions of quality and safety of bivalve shellfish among populations along Niger delta coastline. A clustered based sampling procedure was applied to carry out consumer survey on bivalve shellfish perceptions of quality and safety at four locations along the Atlantic coastline of Niger delta. This was carried out through the use open questionnaire administered through direct interview. Results showed a significant relationship (p<0.05) between some socio-economic attributes and perceptions toward bivalve shellfish consumption. A strong effects of these variables on perception towards bivalve was observed in mean scores of the determined variables. All bivalve species were adjudged to be easily available and cheap implying that bivalve shellfish is a low priced product. Bivalve consumers were conscious of the effects of environmental pollution on the product quality and safety but do not make it a pre-condition before purchasing the product. Over 22% of the consumers have experienced negative health related conditions such as stomach ache, diarrhea and vomiting which were attributed to bivalve consumption. The culinary tradition of consuming bivalve shellfish fresh or slightly cooked raised serious concerned about their safety and tendency to increase risks to consumers’ health. This survey would avail stakeholders in bivalve shellfish related businesses with adequate knowledge on the safety and possible source of risk to consumers

Betanodaviruses are small ssRNA viruses responsible for viral encephalopathy and retinopathy, otherwise known as viral nervous necrosis, in marine fish worldwide. These viruses can be either horizontally or vertically transmitted and have been sporadically detected in invertebrates, which seem to be one of the possible viral sources. Twenty-eight new betanodavirus strains were retrieved in three molluscs species collected from different European countries between 2008 and 2015. The phylogenetic analyses revealed that strains retrieved from bivalve molluscs are closely related to viruses detected in finfish in Southern Europe in the period 2000-2009. Nevertheless, a new betanodavirus strain, markedly different from the other members of the RGNNV genotype, was detected. Such a massive and varied presence of betanodaviruses in bivalve molluscs greatly stresses the risks of transmission previously feared for other invertebrates. Bivalve molluscs reared in the same area as farmed and wild finfish could act as a reservoir of the virus. Furthermore, current European regulations allow relaying activities and the sale of live bivalve molluscs, which could pose a real risk of spreading betanodaviruses across different geographic regions. To our knowledge, this is the first study, which focuses on the detection and genetic characterization of betanodaviruses in bivalve molluscs.

The inner layer of many bivalve and gastropod molluscs consists of iridescent nacre, a material that is structured like a brick wall with bricks consisting of crystalline aragonite and mortar of organic molecules. Myostracal layers formed during shell growth at the point of muscle attachment to the shell can be found interspersed within the nacre structure. Little has been done to examine the effect the myostracal layer has on subsequent nacre structure. Here we present data on the structure of the myostracal and nacre layers from a bivalve mollusc, Pinctada fucata. Scanning electron microscope imaging shows the myostracal layer consists of regular crystalline blocks. The nacre before the layer consists of tablets approximately 400 nm thick, while after the myostracal layer the tablets are approximately 500 nm thick. A new technique, imaging polarimetry, indicates that the aragonite crystals within the nacre following the myostracal layer have greater orientation uniformity than before the myostracal layer. The results presented here suggest a possible interaction between the myostracal layer and subsequent shell growth.

Biodynamics of Particle Processing in Bivalve Molluscs: Models, Data, and Future Directions

Bivalve molluscs are filter feeders and can bioaccumulate oocysts of Cryptosporidium. Tiga Lake in Kano State Nigeria is used for recreational, domestic and agricultural purposes by humans and also serves as a source of drinking water for animals. Bivalve molluscs from the lake are consumed by people. This study was conducted to assess the occurrence of Cryptosporidiumspp. in Tiga Lake using edible Anodonta sp., (fresh water mussels) a bivalve mollusc as sentinel. The samples were examined using modified acid fast staining technique and micrometery of the oocysts. 169 and 150 samples of the molluscs were collected from two locations namely Tashan Idi and Rurum, respectively. The organs examined from each of the molluscs were the gastrointestinal tracts (GIT), gills and haemolymph. The mean oocysts load was higher in the GIT (192.50 ± 173.03) than in the other organs, although the difference was not statistically significant (P > 0.05). Of the two sampling sites, 60 (35.50%) and 40 (26.67%) of the molluscs from Tashan Idi and Rurum respectively were positive for the oocysts. However, the difference was not statistically significant (P > 0.05).The micrometry of the oocysts showed that most of them fell within the size range of 4.0 to 4.3 µm and 4.4 to 4.7 µm suggesting that the oocysts encountered in this work might be those of Cryptosporidium parvum and C. meleagridis which infect a wide range of animals and also humans. The result of this study reveals that 27.59% of the bivalve molluscs harboured Cryptosporidium oocysts and this may have public health implications if undercooked molluscs are consumed by humans. Key words: Cryptosporidium, bivalve molluscs, Tiga Lake, bioaccumulate, public health.

The present study illustrates the monitoring results of the assessment of the contamination of 5 species bivalve molluscs by cadmium in shellfish production areas of Dakhla Bay during the period from 2012 to 2020. The analysis of the samples is carried out by mass spectrometry using a mass spectrometer of the kind (ICP-MS). The results of this assessment show a difference in the accumulation of cadmium by species of bivalve molluscs of the two groups, in particular group 2 (burrowing bivalve molluscs) and group 3 (non-burrowing bivalve molluscs). Also, a slight increase in cadmium is noted in the different species of bivalve molluscs filter during the period 2017-2019, in all the shellfish production areas. However, the cadmium levels recorded remain below the toxicity thresholds. A decrease in these levels is clearly detected from the year 2020 in bivalve molluscs from all shellfish production areas of Dakhla bay.

A comparative study of octopine dehydrogenase isoenzymes in gastropod, bivalve and cephalopod molluscs

During the evolutionary history of bivalve and gastropod molluscs, not only all the soft parts, but also the shells have changed considerably since the Cambrian period. Moreover, not only the outer shape of a shell, but also the internal shell microstructure has changed during this time. The internal shell microstructure is different in different species and is remarkably well related to bivalve classification. Therefore, shell structure is available for the phylogenetic study of bivalves and other molluscs. The internal shell microstructure expresses one face of molluscan evolution.

To study the phenotypic characteristics of Aeromonas spp. from environmental and clinical samples in Spain and to cluster these strains by numerical taxonomy. A collection of 202 Aeromonas strains isolated from bivalve molluscs, water and clinical samples was tested for 64 phenotypic properties; 91% of these isolates were identified at species level. Aeromonas caviae was predominant in bivalve molluscs and Aerom. bestiarum in freshwater samples. Cluster analyses revealed eight different phena: three containing more than one DNA-DNA hybridization group but including strains that belong to the same phenospecies complex (Aerom. hydrophila, Aerom. sobria and Aerom. caviae), Aerom. encheleia, Aerom. trota and three containing unidentified Aeromonas strains isolated from bivalve molluscs. Aeromonas spp. are widely distributed in environmental and clinical sources. A selection of 16 of the phenotypical tests chosen allowed the identification of most isolates (91%), although some strains remain unidentified, mainly isolates from bivalve molluscs, suggesting the presence of new Aeromonas species. Numerical taxonomy was not in total concordance with the identification of the studied strains. Numerical taxonomy of Aeromonas strains isolated from different sources revealed the presence of potentially pathogenic Aeromonas spp., especially in bivalve molluscs, and phena with unidentified strains that suggest new Aeromonas species.

Bivalve molluscs are an important food source for living beings, humans included. They are obligated filter feeders, that feed on microalgae, bacteria and organic particles present in the aquatic environment. Accordingly, they could accumulate chemical compounds, marine biotoxins, bacteria and viruses, including human and animal pathogens (Molloy et al., 2013; Serratore et al., 2014), influencing the epidemiology of animal and human infectious diseases (Skar & Mortensen, 2007). This topic has been long investigated for human pathogens. On the other hand, poor studies were available for finfish pathogens. The Ph.D thesis, arranged in three chapters, deals with finfish and human pathogens in bivalve molluscs and focus on betanodavirus presence in these invertebrates, on their interaction with the Redspotted grouper nervous necrosis virus (RGNNV), one species of the genus Betanodavirus, and the development of a method to mitigate bacterial and viral contaminations of bivalve molluscs. Betanodaviruses very closely related to those of finfish have been found widely present in bivalve molluscs. The clams were demonstrated able to take up and then shed viable RGNNV into the surrounding environment through faeces and filtered water into the surrounding environment posing a serious risk for susceptible cohabitant fish species. Finally, a novel Manila clam sea water potassium MPS-based disinfection method was set up to mitigate the impact of bacterial and viral contaminations in bivalve molluscs. The obtained results point out the possible role of bivalve molluscs in the transmission of pathogens to finfish and highlight the needing of surveillance and control activities where a close inter-specific contact is present. The proposed novel disinfection method provides good experimental results and could find wide application in fisheries sector after adequate field tests.

Quantitation and Chromatographic Characterisation of Neuropeptide F (NPF) Immunoreactivity in Molluscan Nervous Tissue Using Region-Specific Antisera