Important Oyster Species Research Articles

Metabolomic and enzymatic markers reveal critical air exposure threshold for Crassostrea hongkongensis quality

Post-harvest air exposure is unavoidable during oyster transportation and storage, yet the physiological tolerance limits and underlying metabolic responses of commercially important oyster species remain poorly understood. While previous studies have focused on immediate post-harvest quality changes, there is limited knowledge about the time-dependent metabolic adaptations that determine product quality during extended air exposure. This study investigated the physiological and metabolic responses of Crassostrea hongkongensis during air exposure at 4 °C, focusing on identifying the optimal period for quality preservation. Using a combination of survival analysis, enzyme activity assays, and metabolomic profiling, we examined oysters exposed to air for up to 18 days, with particular emphasis on the critical first three days. Survival analysis showed 100 % survival rate at 4 °C through day 7, with mortality beginning thereafter, compared to significant mortality observed at 25 °C (complete mortality by day 7) and 37 °C (complete mortality by day 2). Analysis of antioxidant enzyme activities revealed complex, time-dependent changes, with robust responses observed within the first three days, indicating effective stress management. Metabolomic analysis identified 38 differentially abundant metabolites throughout the exposure period. Notably, the metabolic profile at day 3 showed a tendency to revert towards the control state, suggesting a temporary adaptive response. Key findings included stability in total antioxidant capacity (T-AOC) levels during the initial three days and subtle changes in flavor-related compounds, such as slight decreases in glutamate and aspartate levels. Correlation analyses revealed intricate interactions between enzyme activities and metabolites, highlighting complex stress response mechanisms. The relationship between T-AOC and key osmolytes underscored their critical role in maintaining cellular redox balance during the initial exposure period. Our findings suggest that the optimal window for maintaining C. hongkongensis quality during air exposure at 4 °C is within the first three days. During this period, oysters demonstrate effective adaptive responses, maintaining key quality attributes and nutritional value. Beyond this timeframe, the risk of quality degradation increases significantly. These results have important implications for the oyster industry, providing evidence-based guidelines for post-harvest handling, transportation, and storage practices. We recommend limiting air exposure during cold storage to no more than 3 days to ensure optimal product quality and consumer satisfaction.

Seasonal influence on the cultivation of important oyster species and their productivity in east and south eastern coastal plains of Odisha

Seasonal influence on the cultivation of important oyster species and their productivity in east and south eastern coastal plains of Odisha

Reproductive Biology and Spawning Pattern of Oyster Magallana bilineata in Mengkabong Bay, Sabah, Malaysia

Abstract Magallana bilineata is a commercially important oyster species in Malaysia. Despite its economic significance, the biology and ecology of this species, particularly its reproductive cycle, are poorly understood in the region. Therefore, this study aimed to investigate the reproductive cycle of M. bilineata in Mengkabong Bay, Tuaran, Sabah and its correlation with environmental factors. A total of 105 oyster specimens were collected and examined to determine the sex ratio, gonad developmental stages, maturity index (MI), and condition index (CI). The results revealed a sex ratio of 1:2.36 (♂:♀) in the oyster population of the bay, with a significantly higher proportion of females (P < 0.05). Hermaphroditism was detected in 1.90% of the samples. M. bilineata was found to spawn throughout most months in the bay, with the highest MI and CI values recorded in November 2019 when most oysters were in mature or maturing stages. Salinity was found to be the primary factor influencing male gonad maturation, while temperature was the primary factor influencing female gonad maturation. Understanding the reproductive biology of this species is crucial for predicting its future survival and facilitating assisted spawning and hatchery spat production, thereby ensuring the conservation and sustainability of the oyster fishery in Malaysia.

Comprehensive review on oyster mushroom species (Agaricomycetes): Morphology, nutrition, cultivation and future aspects

Huge volumes of organic matter are produced on earth via photosynthesis and their disposal is a serious threat to the environment and public health all over the world. Nevertheless, these agricultural wastes possess a chemical composition conducive to mushroom cultivation. Lignocellulosic wastes, comprising cellulose, hemicellulose and lignin, offer vital nutrients for mushroom growth. Oyster mushrooms are well known for their unique ability to degrade lignocellulosic materials, making them valuable contributors to the process of organic waste decomposition and nutrient cycling in ecosystems. Employing agricultural by-products as a substrate for mushroom cultivation presents a sustainable approach to waste reduction and the production of nutritionally enriched food. Cultivating oyster mushrooms, presents an economically feasible and environment friendly method of transforming waste materials into highly nutritious food. These edible mushrooms are widely grown worldwide, comprising around 27 percent of the total global production. Oyster cultivation has rapidly increased in Asia due to its low production technology, easy availability of substrates, temperature tolerance and high yield capacity. Oyster mushrooms are sought after as a functional food due to their appealing taste, aroma, flavor, nutritional benefits and medicinal properties. They contain high levels of protein, fiber, vitamins B complex, C and D2, as well as minerals like potassium, phosphorus, selenium, zinc and essential amino acids. These mushrooms are versatile, as they thrive in both tropical and temperate regions without requiring complex controlled environmental conditions for growth. This review article provides insights into the cultivation aspects of important oyster species including a novel species called Hypsizygus ulmarius. Oyster mushroom cultivation is rapidly growing in developing countries, where it can contribute to food security for the world's growing population, which is expected to reach 9.7 billion by 2050.

Integrating Information from the Past into Oyster Management

In the United States, the eastern oyster (Crassostrea virginica) is an economically, culturally, and ecologically important oyster species that ranges from Maine to Texas. Eastern oyster populations are managed by a variety of federal, state, and local governments as well as non-governmental organizations. In addition, the long history of oyster harvesting and coastal land use change in the United States, and asynchronous fluctuations in abundance across the species range due to diverse pressures (e.g., hydrological changes, pollution, disease, overharvesting), combined with often scarce historical monitoring records documenting the timing and magnitude of the changes, have challenged oyster applied professionals for well over a century. The Oysters Past Working Group (OPWG) brings together academic researchers (paleoecologists, archaeologists, and historical ecologists) and applied professionals, representing federal, state, and local government and non-governmental organizations tasked with conserving, managing, and/or restoring oyster populations and habitat. The primary goals of the OPWG are to: 1) identify priority research directions for academic researchers by evaluating the information needs among applied professionals and the types of information from the past that may be able to address them; 2) create a guidance document on best practices for applying information from the past to oyster management; and 3) build trust and commitment to promote longer-lasting and sustained collaboration between academic researchers and applied professionals.

Limited impact of a bioeroding sponge, Cliona sp., on Ostrea chilensis from Foveaux Strait, New Zealand.

Bioeroding sponges can cause extensive damage to aquaculture and wild shellfish fisheries. It has been suggested that heavy sponge infestations that reach the inner cavity of oysters may trigger shell repair and lead to adductor detachment. Consequently, energy provision into shell repair could reduce the energy available for other physiological processes and reduce the meat quality of commercially fished oysters. Nevertheless, the impacts of boring sponges on oysters and other shellfish hosts are inconclusive. We studied the interaction between boring sponges and their hosts and examined potential detrimental effects on an economically important oyster species Ostrea chilensis from Foveaux Strait (FS), New Zealand. We investigated the effect of different infestation levels with the bioeroding sponge Cliona sp. on commercial meat quality, condition, reproduction, and disease susceptibility. Meat quality was assessed with an index based on visual assessments used in the FS O. chilensis fishery. Meat condition was assessed with a common oyster condition index, while histological methods were used to assess sex, gonad stage, reproductive capacity, and pathogen presence. Commercial meat quality and condition of O. chilensis were unaffected by sponge infestation. There was no relationship between sex ratio, gonad developmental stage, or gonad index and sponge infestation. Lastly, we found no evidence that sponge infestation affects disease susceptibility in O. chilensis. Our results suggest that O. chilensis in FS is largely unaffected by infestation with Cliona sp. and therefore reinforces the growing body of evidence that the effects of sponge infestation can be highly variable among different host species, environments, and habitats.

Epigenetic-associated phenotypic plasticity of the ocean acidification-acclimated edible oyster in the mariculture environment.

For marine invertebrates with a pelagic-benthic life cycle, larval exposure to ocean acidification (OA) can affect adult performance in response to another environmental stressor. This carry-over effect has the potential to alter phenotypic traits. However, the molecular mechanisms that mediate "OA"-triggered carry-over effects have not been explored despite such information being key to improving species fitness and management strategies for aquafarming. This study integrated the genome-wide DNA methylome and transcriptome to examine epigenetic modification-mediated carry-over OA impacts on phenotypic traits of the ecologically and commercially important oyster species Crassostrea hongkongensis under field conditions. Larvae of C. hongkongensis were exposed to control pH8.0 and low pH7.4 conditions, mimicking near future OA scenario in their habitat, before being outplanted as post-metamorphic juveniles at two mariculture field sites with contrasting environmental stressors for 9months. The larval carry-over OA effect was found to have persistent impacts on the growth and survival trade-off traits on the outplanted juveniles, although the beneficial or adverse effect depended on the environmental conditions at the outplanted sites. Site-specific plasticity was demonstrated with a diverse DNA methylation-associated gene expression profile, with signal transduction and the endocrine system being the most common and highly enriched functions. Highly methylated exons prevailed in the key genes related to general metabolic and endocytic responses and these genes are evolutionarily conserved in various marine invertebrates in response to OA. These results suggest that oysters with prior larval exposure history to OA had the ability to trigger rapid local adaptive responses via epigenetic modification to cope with multiple stressors in the field.

Feasibility of interspecific hybridization between Iwagaki oyster, Crassostrea nippona and Portuguese oyster, Crassostrea angulata

Iwagaki oyster, Crassostrea nippnoa is famous for its unique flavor and delicacy, while the Portuguese oyster, C. angulata has become an important oyster species in aquaculture because of its high growth rate and high market demand. For the first time, 2 × 2 factorial hybridization between them was performed, forming four groups, including C. nippona♀ × C. nippona♂ (NN), C. nippona♀ × C. angulata♂ (NA), C. angulata♀ × C. nippona♂ (AN), C. angulata♀ × C. angulata♂ (AA). The results showed that fertilization only occurred in NA, not in AN. The cleaved rate, D larvae rate and larvae survival level of NA were remarkably lower than those of the two pure parent groups, but the survival rate of NA and NN was comparable during the grow out stage. NA has no growth heterosis in larval stage, but has obvious growth heterosis in growth stage. On 360th day, the mid-heterosis of NA was 10.76 for shell height, and 26.60 for wet weight, respectively. Like the progenies of pure parents, the gonads of NA hybrids develop normally and can produce gametes. The shell morphology of NA was similar to that of NN and has a strong maternal effect. These results demonstrate that the eggs of C. nippona can be fertilized with the sperm of C. angulata through one way fertilization, and can produce viable hybrids with growth heterosis at the grow-out stage. NA hybrids have good application potential in aquaculture.

Physiological Variation in Response to Vibrio and Hypoxia by Aquacultured Eastern Oysters in the Southeastern United States.

Eastern oysters (Crassostrea virginica) have long been recognized as model organisms of extreme environmental tolerance, showing resilience to variation in temperature, salinity, hypoxia, and microbial pathogens. These phenotypic responses, however, show variability between geographic locations or habitats (e.g., tidal). Physiological, morphological, and genetic differences occur in populations throughout a species' geographical range, which may have been shaped by regional abiotic and biotic variations. Few studies of C. virginica have explored the combined factors of physiological mechanisms of divergent phenotypes between locations and the genetic relationships of individuals between these locations. To characterize genetic relationships of four locations with aquacultured oysters along the North Carolina and Virginia coast, we sequenced a portion of cytochrome oxidase subunit I (COI) that revealed significant variation in haplotype distribution between locations. We then measured mitochondrial physiology and expression of the innate immunity response of hemocytes to lab acclimation and combined stress conditions to compare basal expression and stress response in oysters between these locations. For stress sensing genes, toll-like receptors had the strongest location-specific response to hypoxia and Vibrio, whereas mannose receptor and a stress-receptor were specific to hypoxia and bacteria, respectively. The expression of stress response genes also showed location-specific and stressor-specific changes in expression, particularly for big defensin and the complement gene Cq3. Our results further suggested that genetic similarity of oysters from different locations was not clearly related to physiological and molecular responses. These results are informative for understanding the range of physiological plasticity for stress responses in this commercially important oyster species. They also have implications in the oyster farming industry as well as conservation efforts to restore endangered native oyster beds.

Effects of stocking density on the aquaculture performance of diploid and triploid, Pacific oysterCrassostrea gigasand Portuguese oysterC. angulatain warm water aquaculture

The Pacific oyster (Crassostrea gigas) and the Portuguese oyster (C. angulata) are important oyster species for commercial aquaculture. In this study, three stocking density regimes, including 20, 30 and 40 oysters/basket, were used to study the effects of stocking density on growth performance, survival rate and lipid nutritional quality of diploid and triploid C. gigas and C. angulata. The experiment lasted 163 days, from to 22 November 2011 to 3 April 2012. The main findings of this study are as follows: (1) C. gigas has growth advantage over C. angulata in Shantou waters; (2) geographic origin of the oysters has an impact on the overall performance of diploid and triploid oysters; (3) triploids are generally no growth and survival advantage over diploids in spring and summer; (4) oysters at low stocking density were generally outperformed those at high stocking density; (5) lipid composition of oysters is not affected by ploidy and stocking density; (6) in Shantou waters, C. angulata is more nutritious than C. gigas. This study compares the performance of C. gigas and C. angulata triploidy for the first time. The findings of this study can provide useful information to be applied in oysters aquaculture.

Oyster biomineralization under ocean acidification: From genes to shell.

Biomineralization is one of the key processes that is notably affected in marine calcifiers such as oysters under ocean acidification (OA). Understanding molecular changes in the biomineralization process under OA and its heritability, therefore, is key to developing conservation strategies for protecting ecologically and economically important oyster species. To do this, in this study, we have explicitly chosen the tissue involved in biomineralization (mantle) of an estuarine commercial oyster species, Crassostrea hongkongensis. The primary aim of this study is to understand the influence of DNA methylation over gene expression of mantle tissue under decreased ~pH 7.4, a proxy of OA, and to extrapolate if these molecular changes can be observed in the product of biomineralization-the shell. We grew early juvenile C. hongkongensis, under decreased ~pH 7.4 and control ~pH 8.0 over 4.5months and studied OA-induced DNA methylation and gene expression patterns along with shell properties such as microstructure, crystal orientation and hardness. The population of oysters used in this study was found to be moderately resilient to OA at the end of the experiment. The expression of key biomineralization-related genes such as carbonic anhydrase and alkaline phosphatase remained unaffected; thus, the mechanical properties of the shell (shell growth rate, hardness and crystal orientation) were also maintained without any significant difference between control and OA conditions with signs of severe dissolution. In addition, this study makes three major conclusions: (1) higher expression of Ca2+ binding/signalling-related genes in the mantle plays a key role in maintaining biomineralization under OA; (2) DNA methylation changes occur in response to OA; however, these methylation changes do not directly control gene expression; and (3) OA would be more of a 'dissolution problem' rather than a 'biomineralization problem' for resilient species that maintain calcification rate with normal shell growth and mechanical properties.

Transgenerational responses to seawater pH in the edible oyster, with implications for the mariculture of the species under future ocean acidification

The majority of common edible oysters are projected to grow more slowly and have smaller impaired shells because of anthropogenic CO2-induced reductions in seawater carbonate ion concentration and pH, a process called ocean acidification (OA). Recent evidence has shown that OA has carryover effects, for example, larvae exposed to OA will also exhibit either positive or negative effects after metamorphosis. This study examined the hidden carryover effects of OA exposure during parental and larval stages on post-metamorphic traits of the commercially important oyster species Crassostrea hongkongensis. Adults of C. hongkongensis were exposed to control pH (pHNBS 8.0) and OA-induced low pH (pHNBS 7.4) conditions. Their larval offspring were then exposed to the same aquarium conditions before being out-planted as post-metamorphic juveniles at a mariculture site for 10 months. Initially, larval offspring were resilient to low pH with or without parental exposure. The larvae exposed to low pH had significantly faster development and higher percentage of settlement success compared to control groups. The out-planted juveniles with parental exposure had improved survival and growth compared to juveniles without parental exposure, regardless of the larval exposure history. This implies that transgenerational effects due to parental exposure not only persists but also have a greater influence than the within-generational effects of larval exposure. Our results shed light on the importance of linking the various life history stages when assessing the OA-induced carryover capacity of C. hongkongensis in the natural environment. Understanding these linked relationships helps us better predict the species rapid adaptation responses in the face of changing coastal conditions due to OA.

Preferential Parasitism of Native Oyster Ostrea edulis Over Non-Native Magallana gigas by a Polydorid Worm

Parasites are important structural components of marine communities that can affect organism fitness and ecological interactions, and the provision of ecosystem services. Here, we investigate the host association of Polydora ciliata with two ecologically and economically important oyster species (Ostrea edulis, Magallana gigas) and examine its impacts on two fitness aspects: condition and shell strength. Our results provide strong inferential evidence of host specificity by P. ciliata with a tendency towards infestation of the native O. edulis over the introduced M. gigas. Evidence suggests increasing prevalence of parasitism with organismal age, but no clear indication that parasitism leads to reduced condition or shell strength. The prevalence of infection of O. edulis by P. ciliata over M. gigas observed here holds potential implications for species competition and dominance, and their respective population maintenance, which could explain the much lower abundances of O. edulis compared to M. gigas at specific geographical locations. Additionally, these results hold significance for the aquaculture sector, with parasitism likely to lower production output and decrease the end-product market value.

Ocean acidification reduces hardness and stiffness of the Portuguese oyster shell with impaired microstructure: a hierarchical analysis

Abstract. The rapidly intensifying process of ocean acidification (OA) due to anthropogenic CO2 is not only depleting carbonate ions necessary for calcification but also causing acidosis and disrupting internal pH homeostasis in several marine organisms. These negative consequences of OA on marine calcifiers, i.e. oyster species, have been very well documented in recent studies; however, the consequences of reduced or impaired calcification on the end-product, shells or skeletons, still remain one of the major research gaps. Shells produced by marine organisms under OA are expected to show signs of dissolution, disorganized microstructure and reduced mechanical properties. To bridge this knowledge gap and to test the above hypothesis, we investigated the effect of OA on juvenile shells of the commercially important oyster species, Magallana angulata, at ecologically and climatically relevant OA levels (using pH 8.1, 7.8, 7.5, 7.2). In lower pH conditions, a drop of shell hardness and stiffness was revealed by nanoindentation tests, while an evident porous internal microstructure was detected by scanning electron microscopy. Crystallographic orientation, on the other hand, showed no significant difference with decreasing pH using electron back-scattered diffraction (EBSD). These results indicate the porous internal microstructure may be the cause of the reduction in shell hardness and stiffness. The overall decrease of shell density observed from micro-computed tomography analysis indicates the porous internal microstructure may run through the shell, thus inevitably limiting the effectiveness of the shell's defensive function. This study shows the potential deterioration of oyster shells induced by OA, especially in their early life stage. This knowledge is critical to estimate the survival and production of edible oysters in the future ocean.

Comparative sensitivity of Crassostrea angulata and Crassostrea gigas embryo-larval development to As under varying salinity and temperature

Oysters are a diverse group of marine bivalves that inhabit coastal systems of the world's oceans, providing a variety of ecosystem services, and represent a major socioeconomic resource. However, oyster reefs have become inevitably impacted from habitat destruction, overfishing, pollution and disease outbreaks that have pushed these structures to the break of extinction. In addition, the increased frequency of climate change related events promise to further challenge oyster species survival worldwide.Oysters' early embryonic development is likely the most vulnerable stage to climate change related stressors (e.g. salinity and temperature shifts) as well as to pollutants (e.g. arsenic), and therefore can represent the most important bottleneck that define populations' survival in a changing environment. In light of this, the present study aimed to assess two important oyster species, Crassostrea angulata and Crassostrea gigas embryo-larval development, under combinations of salinity (20, 26 and 33), temperature (20, 24 and 28 °C) and arsenic (As) exposure (0, 30, 60, 120, 240, 480, 960 and 1920 μg. As L−1), to infer on different oyster species capacity to cope with these environmental stressors under the eminent threat of climate change and increase of pollution worldwide.Results showed differences in each species range of salinity and temperature for successful embryonic development. For C angulata, embryo-larval development was successful at a narrower range of both salinity and temperature, compared to C. gigas.Overall, As induced higher toxicity to C. angulata embryos, with calculated EC50 values at least an order of magnitude lower than those calculated for C. gigas.The toxicity of As (measured as median effective concentration, EC50) showed to be influenced by both salinity and temperature in both species. Nonetheless, salinity had a greater influence on embryos' sensitivity to As. This pattern was mostly noticed for C. gigas, with lower salinity inducing higher sensitivity to As. Results were discussed considering the existing literature and suggest that C. angulata populations are likely to become more vulnerable under near future predictions for temperature rise, salinity shifts and pollution.

Native and exotic oysters in Brazil: Comparative tolerance to hypercapnia

Environmental hypercapnia in shallow coastal marine ecosystems can be exacerbated by increasing levels of atmospheric CO2. In these ecosystems organisms are expected to become increasingly subjected to pCO2 levels several times higher than those inhabiting ocean waters (e.g.: 10,000µatm), but still our current understanding on different species capacity to respond to such levels of hypercapnia is limited. Oysters are among the most important foundation species inhabiting these coastal ecosystems, although natural oyster banks are increasingly threatened worldwide. In the present study we studied the effects of hypercapnia on two important oyster species, the pacific oyster C. gigas and the mangrove oyster C. brasiliana, to bring new insights on different species response mechanisms towards three hypercapnic levels (ca. 1,000; 4,000; 10,000 µatm), by study of a set of biomarkers related to metabolic potential (electron transport system - ETS), antioxidant capacity (SOD, CAT, GSH), cellular damage (LPO) and energetic fitness (GLY), in two life stages (juvenile and adult) after 28 days of exposure.Results showed marked differences between each species tolerance capacity to hypercapnia, with contrasting metabolic readjustment strategies (ETS), different antioxidant response capacities (SOD, CAT, GSH), which generally allowed to prevent increased cellular damage (LPO) and energetic impairment (GLY) in both species. Juveniles were more responsive to hypercapnia stress in both congeners, and are likely to be most sensitive to extreme hypercapnia in the environment. Juvenile C. gigas presented more pronounced biochemical alterations at intermediate hypercapnia (4,000µatm) than C. brasiliana. Adult C. gigas showed biochemical alterations mostly in response to high hypercapnia (10,000µatm), while adult C. brasiliana were less responsive to this environmental stressor, despite presenting decreased metabolic potential.Our data bring new insights on the biochemical performance of two important oyster species, and suggest that the duration of extreme hypercapnia events in the ecosystem may pose increased challenges for these organisms as their tolerance capacity may be time limited.

Biochemical alterations in native and exotic oyster species in Brazil in response to increasing temperature

The increase of temperature in marine coastal ecosystems due to atmospheric greenhouse gas emissions is becoming an increasing threat for biodiversity worldwide, and may affect organisms' biochemical performance, often resulting in biogeographical shifts of species distribution. At the same time, the introduction of non-native species into aquatic systems also threatens biodiversity and ecosystem functions. Oysters are among the most valuable socio economic group of bivalve species in global fishery landings, and also provide numerous ecosystem services. However, the introduction of non-native oyster species, namely Crassostrea gigas for aquaculture purposes may threaten native oyster species, mainly by out competing their native congeners. It is therefore of upmost importance to understand physiological and biochemical responses of native and introduced oyster species in a scenario of global temperature rise, in order to provide knowledge that may allow for better species management. Hence, we compared biochemical alterations of the introduced C. gigas and the native Crassostrea brasiliana, the most important oyster species in Brazil, in response to different thermal regimes for 28days (24, 28 and 32°C). For this, metabolism (ETS), energy content (GLY), antioxidant system (SOD, CAT and GSH/GSSG) and cellular damage (LPO) were assessed in adult and juvenile specimens of both species. Juvenile C. gigas were the most affected by increased temperatures, presenting higher mortality, more pronounced antioxidant response (SOD), whereas adults were more tolerant than juveniles, showing no mortality, no significant changes in antioxidant enzymes activity neither energy expenditure. Native C. brasiliana juveniles presented lower mortality and less pronounced biochemical alterations were noted at higher temperature comparing to non-native C. gigas juveniles. Adult C. brasiliana were the least responsive to tested temperatures. Results obtained in this study bring interesting new insights on different oyster species life stages' physiological and biochemical tolerance towards thermal stress. The native species C. brasiliana showed ability to maintain biochemical performance at higher temperatures, with less pronounced biochemical changes than the non-native species. The introduced (C. gigas) showed to be more sensitive, presenting biochemical alterations to cope with the increase of temperature. Despite the lower observed fitness of the introduced species to temperatures closer to those naturally experienced by the native species, the ability of C. gigas to cope with higher temperatures should still raise concerns towards the native species C. brasiliana management and protection.

Evaluation of surface water and sediment quality in Chicalim Bay, Nerul Creek, and Chapora Bay from Goa coast, India-a statistical approach.

To better understand the spatial and temporal variation in surface water and sediment quality, parameters were evaluated from the three sites Chicalim Bay (CB), Nerul Creek (NC), and Chapora Bay (ChB) along the Goa coast, which has major oyster beds. Multivariate analysis such as cluster analysis (CA), Box-Whisker plot (Box plot), and principle component analysis (PCA) revealed that nitrate (NO3-N), nitrite (NO2-N), phosphate (PO4-P), particulate organic carbon (POC), total suspended solids (TSS), dissolved oxygen (DO), and phaeopigments are the responsible parameters for spatio-temporal variability among the studied sites. Results showed an elevated level of ecotoxicological hazard at CB while moderate toxicological risks were observed for organisms at NC. In contrast, ChB was considerably pristine compared with other two sampling sites. Results of present study showed marked dominance of nutrients, phaeopigments, POC, and TSS at CB and NC. The increased levels of these parameters are attributed to the anthropogenic activities which may cause potential risk to humans via consumption of oysters. Therefore, we suggest monitoring heavy metal concentrations in tissue of commercially important oyster species, and their ambient environment (water and sediment) from these estuaries is necessary to create a comprehensive pollution database.

Development of a DNA Microarray-Based Identification System for Commercially Important Korean Oyster Species

ABSTRACT The correct identification of oyster species is essential for both aquaculture and taxonomic study, but it has often been a challenging task due to enormous morphological variation in shell morphs with ecophenotypic origins. The difficulty of species identification based entirely on shell characters has raised the need for developing an accurate, rapid tool for the identification and discrimination of oyster species. In this study, a DNA microarray-based identification system was established for eight commercially important oyster species (Crassostrea ariakensis, Crassostrea gigas, Crassostrea sikamea, Crassostrea nippona, Crassostrea angulata, Ostrea circumpicta, Ostrea denselamellosa, and Saccostrea kegaki). Sixteen species-specific probes developed in this study unambiguously distinguished eight target oyster species with no false-positive or false-negative signals. Of the eight oyster species examined, three Crassostrea species, C. angulata, C. gigas, and C. sikamea, which are indistinguishab...

Parasite Inspection in Five Commercially Important Oyster Species (Mollusca: Bivalvia) of Pakistan

A total of five native oyster species namely; Crassostrea gryphoides, C. madrasensis, C. glomerata, Ostrea nomades and Saccostrea cucullata were collected from three sites: Buleji of Sindh coast; Hub and Jiwani of Balochistan coast, Pakistan. Parasitic inclusion was present only in histological sections of O. nomades and S. cucullata at Buleji.Individuals of O. nomades found to be infected with protozoan parasite Nematopsis speciesand Proctoeces sp. trematodeparasite. Additionally, unknown parasitic cyst was observed at outer epithelium in a male gonadal section of S. cucullata. There is no previous record in literature of pathogens in oyster species at Buleji.