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Standish K. Allen - One of the best experts on this subject based on the ideXlab platform.
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A classification system for gonad development in triploid Crassostrea Virginica
Aquaculture, 2020Co-Authors: Joseph L. Matt, Standish K. AllenAbstract:Abstract Triploidy is a common form of genetic improvement that confers benefits associated with reduced fecundity. Triploid oysters produce fewer gametes yet undergo gametogenesis and develop gonads to variable extents. The variable and typically abnormal gonad development in triploid oysters has often been summarized using criteria developed for the more uniform development of diploid oysters, which can lead to misleading characterizations. Classification systems designed for triploid oysters, such as that for triploid Crassostrea gigas, have allowed for less subjectivity, more repeatability, and have engendered hypotheses of developmental pathways specific to triploids. Despite recent interest in gametogenesis of triploid Crassostrea Virginica in connection with mortality events, gonad development in triploid C. Virginica has primarily been summarized using criteria developed for diploid oysters. In this work, a novel classification system was developed for gonad development in triploid C. Virginica while examining triploids and diploids sampled regularly from a site with and a site without a “triploid mortality” event. Triploids were classified based on the type of gonia present, presence of spermatogenic cells or oocytes, and relative abundance of gametes. The system developed for triploid C. Virginica was in stark contrast to the previously characterized system for triploid C. gigas. A relationship between the nature of the gonia and fecundity, as described for triploid C. gigas, was absent, and instead, we hypothesize that the nature of the gonia indicates sex. Regular, “normal” gonia were associated with male triploids, whereas irregular gonia indicated female lineages. Pathways for gonad development in triploid C. Virginica are proposed based on anatomical observations and time series data. Gonads were mostly similar for triploids at the affected (exhibiting triploid mortality) site and control site as well as between moribund and live triploids sampled during the mortality event. The specific anatomy of gonad development appears unlinked to triploid mortality; however, underlying metabolic processes during gametogenesis remain the leading culprit.
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Performance of selectively-bred lines of eastern oyster, Crassostrea Virginica, across eastern US estuaries
Aquaculture, 2016Co-Authors: Dina A. Proestou, Bryan T. Vinyard, Ryan J. Corbett, Jessica Piesz, Jessica M. Small, Standish K. Allen, Cui Li, Gregory DebrosseAbstract:Abstract Eastern oyster, Crassostrea Virginica , aquaculture has expanded greatly in recent years, but further growth of the industry is constrained by disease-related losses. Oyster breeding programs supporting the oyster aquaculture industry along the east coast of the US have targeted resistance to three prominent diseases: MSX, Dermo, and ROD, caused by Haplosporidium nelsoni , Perkinsus marinus , and Roseovarius crassostreae respectively. Consequently, selected oyster lines possess some level of resistance and/or tolerance but the extent to which these lines, derived from various programs, perform across diverse growing environments used by industry has not been tested. The performance of six selected eastern oyster lines was evaluated at five sites along the east coast of the US (Maine to Virginia) to 1) identify differences in performance among lines at each site, and 2) identify lines that perform well across all sites. Performance measures included growth, mortality, and yield over a 15-month evaluation period. During unusually high mortality events, subsets of oysters were processed for disease diagnosis. Growth trajectories were similar among lines within a site, but varied significantly across sites (78% of random variance explained). Oysters grown in Rhode Island were largest while oysters grown in Maine were smallest at the end of the study. Mortality varied greatly among lines at each site as well as among sites. Line × site interaction explained 61% of the total random variance in the mortality data. In Maine, extensive mortality was observed early in the year for all lines, coincident with increased ROD prevalence. In New Jersey and Virginia, unusually high mortality was evident in the UMFS, Clinton, and NEH-RI lines during the final months of the experiment when the prevalence of both Dermo and MSX were 100% and Statement of relevance First to evaluate multiple oyster lines across diverse sites.
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evaluation of cytochalasin b and 6 dimethylaminopurine for tetraploidy induction in the eastern oyster crassostrea Virginica
Aquaculture, 2016Co-Authors: Brittany L Peachey, Standish K. AllenAbstract:Abstract Cytochalasin B (CB) has been used to induce tetraploidy in oysters since the practice began in 1993. However, CB is toxic and presents health risks to hatchery workers who administer the treatment. 6-dimethylaminopurine (6-DMAP) is also an effective cytokinetic inhibitor, and does not carry the health risks of CB. We examined the relative effectiveness of 6-DMAP vs CB for producing tetraploids in the Eastern oyster ( Crassostrea Virginica ). Survival and yield of tetraploids varied widely among the 15 experiments. Larvae resulting from 6-DMAP treatment had higher survival in 11 of the 14 trials on day two and day six/seven. For yield of tetraploids, 10 of 13 6-DMAP treatments had higher proportions of tetraploids on day two and at the second sampling – day six, seven, or nine – 7 of 10 had higher proportions of tetraploids. Tetraploid spat were obtained from the majority of surviving cultures. Based on these results, 6-DMAP can effectively replace CB for inducing polyploidy in C. Virginica , and probably other Crassostrea spp. , due to the success of the treatment, the ease of application, and the reduction in health risk to hatchery workers. This study set the precedent for the use of 6-DMAP on C. Virginica and established a new procedure for inducing tetraploids using triploid eggs. It might be possible to refine the treatment to further optimize yield of tetraploids. Statement of relevance In this manuscript we report a novel method of inducing tetraploid Crassostrea Virginica from triploid eggs using 6-dimethylaminopurine. We compare the efficiency of cytochalasin B and 6-dimethylaminopurine for tetraploid induction. We also report the expected fecundity of triploid C. Virginica females. The method of tetraploidy induction we report here will likely be useful for inducing tetraploidy in other Crassostrea spp.
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Triploid Oysters in the Chesapeake Bay: Comparison of Diploid and Triploid Crassostrea Virginica
Journal of Shellfish Research, 2012Co-Authors: Lionel Dégremont, Anu Frank-lawale, Céline Garcia, Standish K. AllenAbstract:ABSTRACT Diploid and triploid Eastern oysters, Crassostrea Virginica, were tested at 3 sites characterized by low or moderate salinity regimes in the Virginia part of the Chesapeake Bay from November 2005 through October 2007. Both diploid and triploid cultures were replicated 3 times by producing separate spawns from different broodstock. Ploidy had a generally consistent effect on the performance of C. Virginica at the 3 test sites. At the end of the study, in October 2007, and across all sites, triploid oysters had lower cumulative mortality than diploids (-34%), and greater shell height (+25%), whole weight (+88%), and yield (+152%). as well as a higher proportion of market-size oysters (+114%) than diploids. Both diploids and triploids were similarly infected by Perkinsus marinus and, to a lesser extent, by Haplosporidium nelsoni. In a closer look, growth parameters (shell height growth, whole weight, yield, and percentage of marketable oysters) were always higher in triploids than in diploids regard...
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Survival and Growth of Triploid Crassostrea Virginica (Gmelin, 1791) and C. ariakensis (Fujita, 1913) in Bottom Environments of Chesapeake Bay: Implications for an Introduction
Journal of Shellfish Research, 2009Co-Authors: Peter R. Kingsley-smith, Steven M. Allen, Donald W. Meritt, Kennedy T. Paynter, Standish K. Allen, Heather Harwell, M. Lisa Kellogg, Martha W LuckenbachAbstract:Survival and growth of triploid Crassostrea Virginica and triploid C. ariakensis were investigated at four sites surrounding Chesapeake Bay, United States, that varied in salinity, tidal regime, water depth, predation intensity and disease pressure. Four experimental treatments were established at each site: C. Virginica; C. ariakensis; 50:50 of C. Virginica: C. ariakensis; and shell only. Oysters were deployed at mean shell heights of 12.80 mm and 13.85 mm (C. Virginica and C. ariakensis, respectively), at an overall density of 347.5 oysters m -2 . Oyster survival and growth varied significantly with site and species. Survival was significantly higher in C. Virginica than C. ariakensis at the intertidal site, and significantly higher in C. ariakensis than C. Virginica at the highest salinity, subtidal site. Survival did not differ significantly between species at the mid and low salinity, subtidal sites. For both species, survival differed significantly between sites, with lowest survival in both species occurring at the intertidal site. Among the subtidal sites, C. Virginica survival varied inversely with salinity, whereas C. ariakensis had the lowest survival at the mid salinity site. Eight months after deployment C. ariakensis were significantly larger than C. Virginica at all sites. This difference generally persisted throughout the experiment, though the size differences between oyster species at the lowest salinity site were small (< 10%). Shell heights within single-species treatments differed significantly between sites; highest growth rates were observed at the high salinity, subtidal site, whereas lowest growth rates were observed at the high salinity, intertidal site. At low and mid salinity subtidal sites, C. ariakensis shell heights were significantly greater in the single-species treatment compared with the mixed-species treatment. Perkinsus marinus infections occurred in both species at all sites, with prevalences varying between sites. In C. Virginica, moderate and high intensity infections were only common at the two higher salinity sites, whereas infections in C. ariakensis were generally low to rare. Haplosporidium nelsoni infections in C. Virginica were only observed at the two higher salinity sites and prevalences were generally low. Two out of 53 C. ariakensis tested at the high salinity, subtidal site had rare H. nelsoni infections. Bonamia spp. infections were never observed. Our study supports previous laboratory findings and observations from its native range that C. ariakensis survives poorly in intertidal habitats. In subtidal habitats, however, C. ariakensis displayed broad environmental tolerances, often exceeding native oyster survival and growth rates. Post-introduction C. ariakensis populations would be shaped by the survival and growth patterns described here, but also by their reproductive success, larval survival, predator-prey interactions and prevailing disease dynamics.
Pei Qin - One of the best experts on this subject based on the ideXlab platform.
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ecological engineering through the biosecure introduction of kosteletzkya Virginica seashore mallow to saline lands in china a review of 20 years of activity
Ecological Engineering, 2015Co-Authors: Pei Qin, Denise M Seliskar, Ruiming Han, Mingxi Zhou, Huanshi Zhang, Lishan Fan, John L GallagherAbstract:Abstract Over the past 20 years since its introduction, Kosteletzkya Virginica has proved to be one of the optimal halophytes for saline land restoration in China. In six seashore mallow plantations, its well-developed perennial root system promoted the growth of arbuscular mycorrhizal fungus in the rhizosphere, where the fungus’s activity produced total glomalin (TG, ranging from 0.85 to 2.43 mg g −1 soil), with a high ratio of TG/SOC (soil organic carbon) up to 53.29% in six-year-old seashore mallow plantation. K. Virginica ameliorated the condition of saline soils, promoted native species growth, and increased plant diversity in the plantation sites. Seashore mallow contains many bioactive compounds, e.g., polysaccharides, saponins, flavonoids, etc. which have high bioactivity, and could be used as a fodder additive or for the development of health foods. The leaf, flower, stem and root of K. Virginica , serve as raw materials for hierachical development of useful products according to their different properties. This study reviews and summarizes research on K. Virginica in China during the past 20 years since its introduction from the USA. Also, we present guidelines for the planting and use of seashore mallow in China, in terms of an ecological engineering roadmap, which illustrates the process and strategy for the restoration of saline soils and designs for biomass industries based on its production.
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adventitious root growth and relative physiological responses to waterlogging in the seedlings of seashore mallow kosteletzkya Virginica a biodiesel plant
Australian Journal of Crop Science, 2012Co-Authors: Jian Zhou, Yichuan Zhang, Shuwen Wan, Pei QinAbstract:The biodiesel plant Kosteletzkya Virginica has a high tolerance to salt, drought, and waterlogging. To determine the responses of K. Virginica seedlings to waterlogging and subsequent recovery, the responses of three-month old plants during 35 d of waterlogging and another 14 d of recovery after drainage were investigated. Significant phenomena, such as adventitious root formation and increased root porosity in K. Virginica seedlings after waterlogging, were observed. Serious stomata closure was also very serious. Waterlogging decreased the leaf chlorophyll concentration and weakened the photosynthetic capability of K. Virginica. These phenomena were indicated by reduced maximum quantum yield of photosystem II (Fv/Fm), decreased preliminary efficiency of capturing photon (yield), and enhanced non-photochemical quenching (NPQ) in the treated seedlings. However, 14 d after drainage, these impaired characteristics gradually recovered. Statistical analyses indicated that the most significant adaptive mechanism was the generation of adventitious roots, followed by the increased aerenchyma. Stomata closure was the least significant mechanism for the survival of waterlogged K. Virginica seedlings.
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kosteletzkya Virginica an agroecoengineering halophytic species for alternative agricultural production in china s east coast ecological adaptation and benefits seed yield oil content fatty acid and biodiesel properties
Ecological Engineering, 2008Co-Authors: Chengjiang Ruan, Denise M Seliskar, John L Gallagher, Pei Qin, Y Q Guo, Stanley Lutts, Gregory MahyAbstract:Kosteletzkya Virginica, a perennial halophyte, is native to the American salt marsh. It was introduced into China as a potential species to improve tideland and develop ecologically sound saline agriculture. The experimental results in the fields over 10 years indicated that K. Virginica adapts excellently to the tidal flat habitats in China's east coast, with multiple ecobenefits such as landscape beautification, revegetation and providing food source for targeted wildlife or migratory birds. Seed yields of unselected mixed and bred lines were 621 kg/ha and 957 kg/ha, respectively. Oil contents in the seeds of the unselected mixed and bred lines were 17.536% and 20.64%, respectively. The unsaturated fatty acids (70.134%) in the seed oil predominated over the saturated ones (29.866%). Seed oil of K. Virginica could produce a high quality biodiesel, of which the unsaturated C-18 content of the main part was about 68.62% and sulfur content was 0.0003%. Cetane No. and flash point were both higher than those of diesel fuel, and rust class of steel was lower than that of diesel fuel. These indicate that K. Virginica could be used as an agroecoengineering species for alternative agricultural production and for revegetation of salt-affected tidal flats in China's east coast. (c) 2008 Elsevier B.V. All rights reserved.
John L Gallagher - One of the best experts on this subject based on the ideXlab platform.
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ecological engineering through the biosecure introduction of kosteletzkya Virginica seashore mallow to saline lands in china a review of 20 years of activity
Ecological Engineering, 2015Co-Authors: Pei Qin, Denise M Seliskar, Ruiming Han, Mingxi Zhou, Huanshi Zhang, Lishan Fan, John L GallagherAbstract:Abstract Over the past 20 years since its introduction, Kosteletzkya Virginica has proved to be one of the optimal halophytes for saline land restoration in China. In six seashore mallow plantations, its well-developed perennial root system promoted the growth of arbuscular mycorrhizal fungus in the rhizosphere, where the fungus’s activity produced total glomalin (TG, ranging from 0.85 to 2.43 mg g −1 soil), with a high ratio of TG/SOC (soil organic carbon) up to 53.29% in six-year-old seashore mallow plantation. K. Virginica ameliorated the condition of saline soils, promoted native species growth, and increased plant diversity in the plantation sites. Seashore mallow contains many bioactive compounds, e.g., polysaccharides, saponins, flavonoids, etc. which have high bioactivity, and could be used as a fodder additive or for the development of health foods. The leaf, flower, stem and root of K. Virginica , serve as raw materials for hierachical development of useful products according to their different properties. This study reviews and summarizes research on K. Virginica in China during the past 20 years since its introduction from the USA. Also, we present guidelines for the planting and use of seashore mallow in China, in terms of an ecological engineering roadmap, which illustrates the process and strategy for the restoration of saline soils and designs for biomass industries based on its production.
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kosteletzkya Virginica an agroecoengineering halophytic species for alternative agricultural production in china s east coast ecological adaptation and benefits seed yield oil content fatty acid and biodiesel properties
Ecological Engineering, 2008Co-Authors: Chengjiang Ruan, Denise M Seliskar, John L Gallagher, Pei Qin, Y Q Guo, Stanley Lutts, Gregory MahyAbstract:Kosteletzkya Virginica, a perennial halophyte, is native to the American salt marsh. It was introduced into China as a potential species to improve tideland and develop ecologically sound saline agriculture. The experimental results in the fields over 10 years indicated that K. Virginica adapts excellently to the tidal flat habitats in China's east coast, with multiple ecobenefits such as landscape beautification, revegetation and providing food source for targeted wildlife or migratory birds. Seed yields of unselected mixed and bred lines were 621 kg/ha and 957 kg/ha, respectively. Oil contents in the seeds of the unselected mixed and bred lines were 17.536% and 20.64%, respectively. The unsaturated fatty acids (70.134%) in the seed oil predominated over the saturated ones (29.866%). Seed oil of K. Virginica could produce a high quality biodiesel, of which the unsaturated C-18 content of the main part was about 68.62% and sulfur content was 0.0003%. Cetane No. and flash point were both higher than those of diesel fuel, and rust class of steel was lower than that of diesel fuel. These indicate that K. Virginica could be used as an agroecoengineering species for alternative agricultural production and for revegetation of salt-affected tidal flats in China's east coast. (c) 2008 Elsevier B.V. All rights reserved.
Eugene M Burreson - One of the best experts on this subject based on the ideXlab platform.
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pathogens in crassostrea ariakensis and other asian oyster species implications for non native oyster introduction to chesapeake bay
Diseases of Aquatic Organisms, 2007Co-Authors: Jessica Moss, Eugene M Burreson, Jan F Cordes, Christopher F Dungan, Gwynne D Brown, A Wang, Kimberly S ReeceAbstract:With the drastic decline of eastern oyster Crassostrea Virginica populations in the Chesapeake Bay due to over-fishing, diseases and habitat destruction, there is interest in Maryland and Virginia in utilizing the non-native oyster species Crassostrea ariakensis for aquaculture, fishery resource enhancement, and ecological restoration. The International Council for the Exploration of the Sea (ICES) recommends that non-native species be examined for ecological, genetic and disease relationships in the native range prior to a deliberate introduction to a new region. Therefore, a pathogen survey of C. ariakensis and other sympatric oyster species was conducted on samples collected in the PR China, Japan and Korea using molecular diagnostics and histopathology. Molecular assays focused on 2 types of pathogens: protistan parasites in the genus Perkinsus and herpesviruses, both with known impacts on commercially important molluscan species around the world, including Asia. PCR amplification and DNA sequence data from the internal transcribed spacer region of the rRNA gene complex revealed the presence of 2 Perkinsus species not currently found in USA waters: P. olseni and an undescribed species. In addition, 3 genetic strains of molluscan herpesviruses were detected in oysters from several potential C. ariakensis broodstock acquisition sites in Asia. Viral gametocytic hypertrophy, Chlamydia-like organisms, a Steinhausia-like microsporidian, Perkinsus sp., Nematopsis sp., ciliates, and cestodes were also detected by histopathology.
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Dual disease resistance in a selectively bred eastern oyster, Crassostrea Virginica, strain tested in Chesapeake Bay
Aquaculture, 2003Co-Authors: Lisa M. Ragone Calvo, Gustavo W. Calvo, Eugene M BurresonAbstract:Selective breeding efforts have yielded oyster strains, Crassostrea Virginica, with improved survival and resistance against Haplosporidium nelsoni (MSX); however, because of susceptibility to the oyster pathogen Perkinsus marinus (Dermo), their utility has been limited in areas where the two parasites co-occur. Dual resistance to H. nelsoni and P. marinus was achieved through four generations of artificial selection of wild Delaware Bay oyster progeny at a site in the lower York River, Virginia, USA where both diseases are enzootic. During 1993–1995, survival, growth, and disease susceptibility of third generation Delaware Bay (F3-DEBY) oysters were evaluated at the York River site in comparison to that of similarly selected third generation James River, Virginia oysters (F3-JR), and first generation Louisiana oysters (F1-LA), whose parents were naturally selected in the wild for resistance to P. marinus. During 1997–1999, the performance of F4-DEBY was evaluated at three sites in Virginia in comparison to two groups of first generation oysters whose parents originated from Mobjack Bay and Tangier Sound, Virginia where both P. marinus and H. nelsoni are enzootic. In the presence of high infection pressure from both H. nelsoni and P. marinus, the F3-DEBY stock showed significantly higher survival and growth than either the F3-JR or F1-LA strain. After 15 months of deployment, 79% of F3-DEBY, 11% of F3-JR and 17% of F1-LA oysters were market size (≥76.2 mm) and cumulative mortality was only 16% in F3-DEBY as compared to 42% in F3-JR and F1-LA. At the termination of the study, F3-DEBY oysters exhibited 22% lower mortality than the F1-LA stock, which outperformed the F3-JR stock. Relative performance in respect to disease varied considerably with sample date; however, average H. nelsoni weighted prevalence varied such that F3-DEBY
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dual disease resistance in a selectively bred eastern oyster crassostrea Virginica strain tested in chesapeake bay
Aquaculture, 2003Co-Authors: Lisa Ragone M Calvo, Gustavo W. Calvo, Eugene M BurresonAbstract:Selective breeding efforts have yielded oyster strains, Crassostrea Virginica, with improved survival and resistance against Haplosporidium nelsoni (MSX); however, because of susceptibility to the oyster pathogen Perkinsus marinus (Dermo), their utility has been limited in areas where the two parasites co-occur. Dual resistance to H. nelsoni and P. marinus was achieved through four generations of artificial selection of wild Delaware Bay oyster progeny at a site in the lower York River, Virginia, USA where both diseases are enzootic. During 1993–1995, survival, growth, and disease susceptibility of third generation Delaware Bay (F3-DEBY) oysters were evaluated at the York River site in comparison to that of similarly selected third generation James River, Virginia oysters (F3-JR), and first generation Louisiana oysters (F1-LA), whose parents were naturally selected in the wild for resistance to P. marinus. During 1997–1999, the performance of F4-DEBY was evaluated at three sites in Virginia in comparison to two groups of first generation oysters whose parents originated from Mobjack Bay and Tangier Sound, Virginia where both P. marinus and H. nelsoni are enzootic. In the presence of high infection pressure from both H. nelsoni and P. marinus, the F3-DEBY stock showed significantly higher survival and growth than either the F3-JR or F1-LA strain. After 15 months of deployment, 79% of F3-DEBY, 11% of F3-JR and 17% of F1-LA oysters were market size (≥76.2 mm) and cumulative mortality was only 16% in F3-DEBY as compared to 42% in F3-JR and F1-LA. At the termination of the study, F3-DEBY oysters exhibited 22% lower mortality than the F1-LA stock, which outperformed the F3-JR stock. Relative performance in respect to disease varied considerably with sample date; however, average H. nelsoni weighted prevalence varied such that F3-DEBY
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a sensitive and specific dna probe for the oyster pathogen haplosporidium nelsoni
Journal of Eukaryotic Microbiology, 1995Co-Authors: Nancy A Stokes, Eugene M BurresonAbstract:: Haplosporidium nelsoni is a pathogen of the eastern oyster, Crassostrea Virginica, along the middle Atlantic coast of the U.S. Genomic DNA was extracted from H. nelsoni plasmodia and small subunit (SSU) rDNA was amplified by PCR, cloned and sequenced. The sequence of H. nelsoni SSU rDNA was aligned with that of another haplosporidian, Minchinia teredinis, and with SSU rDNA data of C. Virginica and various protists in GenBank. A 21-base oligonucleotide unique to H. nelsoni, designated MSX1347, was commercially synthesized and tested for sensitivity and specificity. In dot blot hybridizations the probe detected 100 pg of cloned H. nelsoni rDNA and the presence of H. nelsoni in 1 microgram of genomic DNA from an infected oyster. It did not hybridize with 1 microgram of genomic DNA from uninfected C. Virginica or with cloned SSU rDNA of M. teredinis. The probe was further tested for specificity with in situ hybridizations on AFA-fixed, paraffin-embedded tissue sections. The probe hybridized well with H. nelsoni plasmodia and immature spores, but poorly with mature spores. The probe did not hybridize with oyster tissue, with other common oyster parasites such as P. marinus or Nematopsis sp., or with the haplosporidians Haplosporidium louisiana from mud crabs (Panopeus spp.), Haplosporidium costale from C. Virginica or M. teredinis from shipworms (Teredo spp.).
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further evidence of regular sporulation by haplosporidium nelsoni in small oysters crassostrea Virginica
Journal of Parasitology, 1994Co-Authors: Eugene M BurresonAbstract:: During a field study to determine the susceptibility of the Pacific oyster Crassostrea gigas to Chesapeake Bay oyster pathogens, sporulation of Haplosporidium nelsoni was observed in eastern oysters Crassostrea Virginica being used as controls. The C. Virginica were obtained from 2 sources on 19 May 1993, a wild population in the upper Rappahannock River, Virginia (59.6 mm mean shell height) and a hatchery-reared population from Chesapeake Mari-culture that was held in the Wye River, Maryland (42.2 mm mean shell height); they were deployed in the York River, lower Chesapeake Bay on 29 June 1993. Both groups of C. Virginica became heavily infected with H. nelsoni in early July 1993. Sporulation was observed in both groups on 8 September but was most prevalent in the smaller Maryland oysters where it reached 36% of infected oysters. Oysters of 72.3 mm mean shell height deployed at the same location in May 1993 also became heavily infected with H. nelsoni, but no cases of sporulation were observed in these larger oysters. These results provide further evidence that sporulation of H. nelsoni occurs regularly only in oysters approximately 1 yr old or less.
Matthew P Hare - One of the best experts on this subject based on the ideXlab platform.
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Transcriptomic analysis of candidate osmoregulatory genes in the eastern oyster Crassostrea Virginica
BMC Genomics, 2014Co-Authors: Laura E Eierman, Matthew P HareAbstract:Background The eastern oyster, Crassostrea Virginica , is a euryhaline species that can thrive across a wide range of salinities (5-35). As with all estuarine species, individual oysters must be able to regulate their osmotic balance in response to constant temporal variation in salinity. At the population level, recurrent viability selection may be an additional mechanism shaping adaptive osmoregulatory phenotypes at the margins of oyster salinity tolerance. To identify candidate genes for osmoregulation, we sequenced, assembled, and annotated the transcriptome of wild juvenile eastern oysters from ‘high’ and ‘low’ salinity regimes. Annotations and candidates were mostly based on the Pacific oyster ( Crassostrea gigas ) genome sequence so osmoregulatory relevance in C. Virginica was explored by testing functional enrichment of genes showing spatially discrete patterns of expression and by quantifying coding sequence divergence. Results The assembly of sequence reads and permissive clustering of potentially oversplit alleles resulted in 98,729 reftigs (contigs and singletons). Of these, 50,736 were annotated with 9,307 belonging to a set of candidate osmoregulatory genes identified from the C. gigas genome. A total of 218,777 SNPs (0.0185 SNPs/bp) were identified in annotated reftigs of C. Virginica . Amino acid divergence between translations of C. Virginica annotated reftigs and C. gigas coding sequence averaged 23.2 % with an average dN/dS ratio of 0.074, suggesting purifying selection on protein sequences. The high and low salinity source oysters each expressed a subset of genes unique to that group, and the functions for these annotated genes were consistent with known molecular mechanisms for osmotic regulation in molluscs. Conclusions Most of the osmoregulatory gene candidates experimentally identified in C. gigas are present in this C. Virginica transcriptome. In general these congeners show coding sequence divergence too high to make the C. gigas genome a useful reference for C. Virginica bioinformatics. However, strong purifying selection is characteristic of the osmoregulatory candidates so functional annotations are likely to correspond. An initial examination of C. Virginica presence/absence expression patterns across the salinity gradient in a single estuary suggests that many of these candidates have expression patterns that co-vary with salinity, consistent with osmoregulatory function in C. Virginica .
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transcriptomic analysis of candidate osmoregulatory genes in the eastern oyster crassostrea Virginica
BMC Genomics, 2014Co-Authors: Laura E Eierman, Matthew P HareAbstract:The eastern oyster, Crassostrea Virginica, is a euryhaline species that can thrive across a wide range of salinities (5-35). As with all estuarine species, individual oysters must be able to regulate their osmotic balance in response to constant temporal variation in salinity. At the population level, recurrent viability selection may be an additional mechanism shaping adaptive osmoregulatory phenotypes at the margins of oyster salinity tolerance. To identify candidate genes for osmoregulation, we sequenced, assembled, and annotated the transcriptome of wild juvenile eastern oysters from ‘high’ and ‘low’ salinity regimes. Annotations and candidates were mostly based on the Pacific oyster (Crassostrea gigas) genome sequence so osmoregulatory relevance in C. Virginica was explored by testing functional enrichment of genes showing spatially discrete patterns of expression and by quantifying coding sequence divergence. The assembly of sequence reads and permissive clustering of potentially oversplit alleles resulted in 98,729 reftigs (contigs and singletons). Of these, 50,736 were annotated with 9,307 belonging to a set of candidate osmoregulatory genes identified from the C. gigas genome. A total of 218,777 SNPs (0.0185 SNPs/bp) were identified in annotated reftigs of C. Virginica. Amino acid divergence between translations of C. Virginica annotated reftigs and C. gigas coding sequence averaged 23.2 % with an average dN/dS ratio of 0.074, suggesting purifying selection on protein sequences. The high and low salinity source oysters each expressed a subset of genes unique to that group, and the functions for these annotated genes were consistent with known molecular mechanisms for osmotic regulation in molluscs. Most of the osmoregulatory gene candidates experimentally identified in C. gigas are present in this C. Virginica transcriptome. In general these congeners show coding sequence divergence too high to make the C. gigas genome a useful reference for C. Virginica bioinformatics. However, strong purifying selection is characteristic of the osmoregulatory candidates so functional annotations are likely to correspond. An initial examination of C. Virginica presence/absence expression patterns across the salinity gradient in a single estuary suggests that many of these candidates have expression patterns that co-vary with salinity, consistent with osmoregulatory function in C. Virginica.
