The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Susan E. Ford - One of the best experts on this subject based on the ideXlab platform.
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Investigating The Life Cycle of Haplosporidium nelsoni (Msx): A Review
Journal of Shellfish Research, 2018Co-Authors: Susan E. Ford, Nancy A. Stokes, Kathryn A. Alcox, Brenda S. Flores Kraus, Robert D. Barber, Ryan B. Carnegie, Eugene M. BurresonAbstract:ABSTRACT Attempts to decipher the life cycle of Haplosporidium nelsoni began almost immediately after it was identified as the pathogen causing MSX disease in eastern oysters, Crassostrea virginica. But transmission experiments failed and the spore stage, characteristic of haplosporidans, was extremely rare. Researchers concluded that another host was involved: an intermediate host in which part of the life cycle was produced, or—if the oyster was an accidental host—an alternate host that produces infective elements. A later finding that spores were found more often in spat (
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investigating the life cycle of Haplosporidium nelsoni msx a review
Journal of Shellfish Research, 2018Co-Authors: Susan E. Ford, Nancy A. Stokes, Kathryn A. Alcox, Robert D. Barber, Ryan B. Carnegie, Brenda Flores S Kraus, Eugene M. BurresonAbstract:ABSTRACT Attempts to decipher the life cycle of Haplosporidium nelsoni began almost immediately after it was identified as the pathogen causing MSX disease in eastern oysters, Crassostrea virginica. But transmission experiments failed and the spore stage, characteristic of haplosporidans, was extremely rare. Researchers concluded that another host was involved: an intermediate host in which part of the life cycle was produced, or—if the oyster was an accidental host—an alternate host that produces infective elements. A later finding that spores were found more often in spat (<1 y old) than in adults revived the idea of direct transmission between oysters. The new findings and the availability of molecular diagnostics led us to revive life cycle investigations. Over several years, oyster spat were examined for spores and searched for H. nelsoni in potential non-oyster hosts using both histological and polymerase chain reaction (PCR) methodologies. Although spores occurred in a high proportion of spat with ...
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quantitative pcr assay to determine prevalence and intensity of msx Haplosporidium nelsoni in north carolina and rhode island oysters crassostrea virginica
Diseases of Aquatic Organisms, 2012Co-Authors: Ami E Wilbur, Susan E. Ford, Julie D Gauthier, Marta GomezchiarriAbstract:: The continuing challenges to the management of both wild and cultured eastern oyster Crassostrea virginica populations resulting from protozoan parasites has stimulated interest in the development of molecular assays for their detection and quantification. For Haplosporidium nelsoni, the causative agent of multinucleated sphere unknown (MSX) disease, diagnostic evaluations depend extensively on traditional but laborious histological approaches and more recently on rapid and sensitive (but not quantitative) end-point polymerase chain reaction (PCR) assays. Here, we describe the development and application of a quantitative PCR (qPCR) assay for H. nelsoni using an Applied Biosystems TaqMan® assay designed with minor groove binder (MGB) probes. The assay was highly sensitive, detecting as few as 20 copies of cloned target DNA. Histologically evaluated parasite density was significantly correlated with the quantification cycle (Cq), regardless of whether quantification was categorical (r2 = 0.696, p < 0.0001) or quantitative (r2 = 0.797, p < 0.0001). Application in field studies conducted in North Carolina, USA (7 locations), revealed widespread occurrence of the parasite with moderate to high intensities noted in some locations. In Rhode Island, USA, application of the assay on oysters from 2 locations resulted in no positives.
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Development of resistance to an introduced marine pathogen by a native host
Journal of Marine Research, 2012Co-Authors: Susan E. Ford, David BushekAbstract:In 1957–1959, the introduced protistan parasite, Haplosporidium nelsoni, killed 90–95% of the oysters (Crassostrea virginica) in lower Delaware Bay and about half of those in the upper bay. Shortly thereafter, H. nelsoni-caused mortality in the wild population of the lower bay declined, approximating that of first-generation selectively bred oysters. For nearly three decades thereafter no further change in survival of the wild population was evident, although steady improvement was achieved by continued selective breeding. Survival of the wild population is thought to have plateaued because the great majority of oysters inhabited the upper bay where they were protected from H. nelsoni infection and selective mortality by low salinity. Consequently, they contributed most of the offspring to the bay population. From 1957 through 1987, H. nelsoni prevalence was cyclic, but overall high (annual maxima of 60 to 85%) in the lower bay. Since 1988, however, prevalence in wild oysters has rarely exceeded 30% anywhere in the bay, even though unselected oysters continue to become heavily infected when exposed, and molecular evidence indicates that the parasite remains present throughout the bay. This apparent “second step” in the development of resistance in the wild oysters occurred after a drought-associated incursion of H. nelsoni into the upper bay in the mid-1980s. Mortalities were widespread, heavy and more extreme than during the 1957–59 epizootic. Resistant survivors of the second epizootic have apparently repopulated the bay. When compared to unselected stocks, common-garden exposure to H. nelsoni of oysters from both upbay and downbay sites indicates that a high degree of resistance to the development of MSX disease has become widespread in the wild oyster population of Delaware Bay after two major selection events separated by nearly 30 years.
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widespread survey finds no evidence of Haplosporidium nelsoni msx in gulf of mexico oysters
Diseases of Aquatic Organisms, 2011Co-Authors: Susan E. Ford, Nancy A. Stokes, Jenny Paterno, Emily Scarpa, Eric N Powell, David BushekAbstract:The advent of molecular detection assays has provided a set of very sensitive tools for the detection of pathogens in marine organisms, but it has also raised problems of how to interpret positive signals that are not accompanied by visual confirmation. PCR-positive results have recently been reported for Haplosporidium nelsoni (MSX), a pathogen of the oyster Crassostrea virginica in 31 of 40 oysters from 6 sites in the Gulf of Mexico and the Caribbean Sea. Histological confirmation of the PCR results was not undertaken, and no haplosporidian has been reported from the numerous histological studies and surveys of oysters in the region. To further investigate the possibility that H. nelsoni is present in this region, we sampled 210 oysters from 40 sites around the Gulf of Mexico and Puerto Rico using PCR and 180 of these using tissue-section histology also. None of the oysters showed evidence of H. nelsoni by PCR or of any haplosporidian by histology. We cannot, therefore, confirm that H. nelsoni is present and widespread in the Gulf of Mexico and the Caribbean Sea. Our results do not prove that H. nelsoni is absent from the region, but taken together with results from previous histological surveys, they suggest that for the purposes of controlling oyster importation, the region should continue to be considered free of the parasite.
Eugene M. Burreson - One of the best experts on this subject based on the ideXlab platform.
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Haplosporidium COSTALE (HAPLOSPORIDIA), AND INCONGRUENCE OF MOLECULAR PHYLOGENY AND SPORE ORNAMENTATION IN THE HAPLOSPORIDIA
2020Co-Authors: Eugene M. Burreson, Kimberly S ReeceAbstract:Spore ornamentation of Haplosporidium nelsoni and Haplosporidium costale was determined by scanning electron microscopy. For H. nelsoni, the spore surface was covered with individual ribbons that were tightly bound together and occurred as a single sheet. In some spores, this layer was overlaid with a network of branching fibers, about 0.05 |xm in diameter, which often was dislodged from the spore at the aboral pole. For H. costale, ornamentation consisted of a sparse network of branching fibers on the spore surface. Molecular phylogenetic analysis of the phylum Haplosporidia revealed that Urosporidium, Bonamia, and Minchinia were monophyletic but that Haplosporidium was paraphyletic. All species of Minchinia have ornamentation composed of epispore cytoplasm, supporting the monophyly of this genus. The presence of spores with a hinged operculum and spore wall-derived ornamentation in Bonamia perspora confounds the distinction between Bonamia and Haplosporidium. Species with ornamentation composed of outer spore wall material and attached to the spore wall do not form a monophyletic group in the molecular phylogenetic analysis. These results suggest that the widely accepted practice of assigning all species with spore wall-derived ornamentation to Haplospordium cannot be supported and that additional genera are needed in which to place some species presently assigned to Haplosporidium.
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Investigating The Life Cycle of Haplosporidium nelsoni (Msx): A Review
Journal of Shellfish Research, 2018Co-Authors: Susan E. Ford, Nancy A. Stokes, Kathryn A. Alcox, Brenda S. Flores Kraus, Robert D. Barber, Ryan B. Carnegie, Eugene M. BurresonAbstract:ABSTRACT Attempts to decipher the life cycle of Haplosporidium nelsoni began almost immediately after it was identified as the pathogen causing MSX disease in eastern oysters, Crassostrea virginica. But transmission experiments failed and the spore stage, characteristic of haplosporidans, was extremely rare. Researchers concluded that another host was involved: an intermediate host in which part of the life cycle was produced, or—if the oyster was an accidental host—an alternate host that produces infective elements. A later finding that spores were found more often in spat (
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investigating the life cycle of Haplosporidium nelsoni msx a review
Journal of Shellfish Research, 2018Co-Authors: Susan E. Ford, Nancy A. Stokes, Kathryn A. Alcox, Robert D. Barber, Ryan B. Carnegie, Brenda Flores S Kraus, Eugene M. BurresonAbstract:ABSTRACT Attempts to decipher the life cycle of Haplosporidium nelsoni began almost immediately after it was identified as the pathogen causing MSX disease in eastern oysters, Crassostrea virginica. But transmission experiments failed and the spore stage, characteristic of haplosporidans, was extremely rare. Researchers concluded that another host was involved: an intermediate host in which part of the life cycle was produced, or—if the oyster was an accidental host—an alternate host that produces infective elements. A later finding that spores were found more often in spat (<1 y old) than in adults revived the idea of direct transmission between oysters. The new findings and the availability of molecular diagnostics led us to revive life cycle investigations. Over several years, oyster spat were examined for spores and searched for H. nelsoni in potential non-oyster hosts using both histological and polymerase chain reaction (PCR) methodologies. Although spores occurred in a high proportion of spat with ...
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declining impact of an introduced pathogen Haplosporidium nelsoni in the oyster crassostrea virginica in chesapeake bay
Marine Ecology Progress Series, 2011Co-Authors: Ryan B. Carnegie, Eugene M. BurresonAbstract:The protistan parasite Haplosporidium nelsoni, the causative agent of MSX (multinucleated sphere X) disease, is notorious for its devastating impacts on populations of the oyster Crassostrea virginica along the midAtlantic coast of the USA. The parasite was introduced from Asia (Burreson et al. 2000) sometime prior to 1957, when it emerged in Delaware Bay; by 1959, oysters were dying of H. nelsoni parasitism also in Chesapeake Bay (Andrews 1962, Haskin et al. 1966). Oyster mortality due to this parasite exceeded 90% on reefs in lower Delaware and Chesapeake Bays during the early years of the epizootic (Ford & Haskin 1982, Haskin & Andrews 1988), an acute impact that presumably reflected a new encounter between an introduced parasite and a naive host (Burreson et al. 2000). H. nel-
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Inter-relationships of haplosporidians deduced from ultrastructural studies.
Diseases of Aquatic Organisms, 2009Co-Authors: P. M. Hine, Ryan B. Carnegie, Eugene M. Burreson, Marc Y. EngelsmaAbstract:We reviewed papers reporting haplosporidian ultrastructure to compare inter-relationships based on ultrastructure with those based on molecular data, to identify features that may be important in haplosporidian taxonomy, and to consider parasite taxonomy in relation to host taxonomy. There were links between the following: (1) the plasmodia of an abalone parasite, Haplosporidium nelsoni and Urosporidium crescens in the release of haplosporosomes; (2) H. costale and H. armoricanum in haplosporosome shape and presence and shape of Golgi in spores; (3) basal asporous crustacean haplosporidians which form haplosporosomes from formative bodies (FBs) in vegetative stages - H. nelsoni, which forms haplosporosomes from FBs in plasmodial cytoplasm, and H. louisiana, Minchinia spp. and Bonamia perspora, which form haplosporosomes from FBs in spores; (4) crustacean haplosporidians, Bonamia spp. and M. occulta in the predominance of uni- and binucleate stages; and (5) lipid-like vesicles in sporoplasms of H. costale, H. armoricanum, H. lusitanicum, H. pickfordi, H. montforti, and B. perspora. In general, these relationships reflect phylogenies based on molecular studies. As well as spore form and ornamentation, haplosporogenesis in spores appears to be taxonomically important. Parasite and host taxonomy were linked in the infection of lower invertebrates by Urosporidium spp., the infection of oysters by Bonamia spp., and of molluscs by Minchinia spp. Haplosporidium spp. are patently an artificial, paraphyletic group probably comprising many taxa. Consequently, the taxonomy of haplosporidians needs a thorough revision.
Nancy A. Stokes - One of the best experts on this subject based on the ideXlab platform.
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Investigating The Life Cycle of Haplosporidium nelsoni (Msx): A Review
Journal of Shellfish Research, 2018Co-Authors: Susan E. Ford, Nancy A. Stokes, Kathryn A. Alcox, Brenda S. Flores Kraus, Robert D. Barber, Ryan B. Carnegie, Eugene M. BurresonAbstract:ABSTRACT Attempts to decipher the life cycle of Haplosporidium nelsoni began almost immediately after it was identified as the pathogen causing MSX disease in eastern oysters, Crassostrea virginica. But transmission experiments failed and the spore stage, characteristic of haplosporidans, was extremely rare. Researchers concluded that another host was involved: an intermediate host in which part of the life cycle was produced, or—if the oyster was an accidental host—an alternate host that produces infective elements. A later finding that spores were found more often in spat (
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investigating the life cycle of Haplosporidium nelsoni msx a review
Journal of Shellfish Research, 2018Co-Authors: Susan E. Ford, Nancy A. Stokes, Kathryn A. Alcox, Robert D. Barber, Ryan B. Carnegie, Brenda Flores S Kraus, Eugene M. BurresonAbstract:ABSTRACT Attempts to decipher the life cycle of Haplosporidium nelsoni began almost immediately after it was identified as the pathogen causing MSX disease in eastern oysters, Crassostrea virginica. But transmission experiments failed and the spore stage, characteristic of haplosporidans, was extremely rare. Researchers concluded that another host was involved: an intermediate host in which part of the life cycle was produced, or—if the oyster was an accidental host—an alternate host that produces infective elements. A later finding that spores were found more often in spat (<1 y old) than in adults revived the idea of direct transmission between oysters. The new findings and the availability of molecular diagnostics led us to revive life cycle investigations. Over several years, oyster spat were examined for spores and searched for H. nelsoni in potential non-oyster hosts using both histological and polymerase chain reaction (PCR) methodologies. Although spores occurred in a high proportion of spat with ...
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the occurrence of haplosporidian parasites Haplosporidium nelsoni and Haplosporidium sp in oysters in ireland
Journal of Invertebrate Pathology, 2013Co-Authors: Sharon A Lynch, Nancy A. Stokes, Antonio Villalba, Elvira Abollo, M Y Engelsma, Sarah C CullotyAbstract:The phylum Haplosporidia is a group of obligate protozoan parasites that infect a number of freshwater and marine invertebrates. Haplosporidian parasites have caused significant mortalities in commercially important shellfish species worldwide. In this study, haplosporidia were detected in Pacific oysters Crassostrea gigas originating in Ireland and were subsequently identified independently in laboratories both in Ireland and in Spain as Haplosporidium nelsoni. In Ireland, H. nelsoni plasmodia were also observed in the heart tissue of a single Ostrea edulis. A range of techniques including heart smear screening, histology, standard polymerase chain reaction (PCR), direct sequencing and in situ hybridisation with an H. nelsoni specific DNA probe were carried out to confirm diagnosis. This is the first reporting of H. nelsoni in oysters in Ireland and this is the first reporting of the detection of this haplosporidian in O. edulis. In Ireland, another haplosporidian was also observed in a single O. edulis during heart smear screening. PCR and DNA sequencing were carried out and indicated the presence of a Haplosporidium sp., most likely Haplosporidium armoricanum. The low prevalence and intensity of infection of both haplosporidian species in Irish C. gigas and in particular O. edulis may indicate that their presence is inconsequential.
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widespread survey finds no evidence of Haplosporidium nelsoni msx in gulf of mexico oysters
Diseases of Aquatic Organisms, 2011Co-Authors: Susan E. Ford, Nancy A. Stokes, Jenny Paterno, Emily Scarpa, Eric N Powell, David BushekAbstract:The advent of molecular detection assays has provided a set of very sensitive tools for the detection of pathogens in marine organisms, but it has also raised problems of how to interpret positive signals that are not accompanied by visual confirmation. PCR-positive results have recently been reported for Haplosporidium nelsoni (MSX), a pathogen of the oyster Crassostrea virginica in 31 of 40 oysters from 6 sites in the Gulf of Mexico and the Caribbean Sea. Histological confirmation of the PCR results was not undertaken, and no haplosporidian has been reported from the numerous histological studies and surveys of oysters in the region. To further investigate the possibility that H. nelsoni is present in this region, we sampled 210 oysters from 40 sites around the Gulf of Mexico and Puerto Rico using PCR and 180 of these using tissue-section histology also. None of the oysters showed evidence of H. nelsoni by PCR or of any haplosporidian by histology. We cannot, therefore, confirm that H. nelsoni is present and widespread in the Gulf of Mexico and the Caribbean Sea. Our results do not prove that H. nelsoni is absent from the region, but taken together with results from previous histological surveys, they suggest that for the purposes of controlling oyster importation, the region should continue to be considered free of the parasite.
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Haplosporidiosis in the pacific oyster Crassostrea gigas from the French Atlantic coast
Diseases of Aquatic Organisms, 2000Co-Authors: Tristan Renault, Nancy A. Stokes, Bruno Chollet, Nathalie Cochennec, Franck Berthe, Andre Gerard, Eugene M. BurresonAbstract:Two cases of haplosporidian infection occurred during 1993 in Pacific oysters Crassostrea gigas from the French Atlantic coast. The localization and ultrastructure of the plasmodia are de- scribed. In situ hybridization of infected tissue sections was conducted with DNA probes for oyster- infecting haplosporidians. The Haplosporidium nelsoni-specific DNA probe MSX1347 hybridized with the C. gigas parasite, and the H. costale-specific probe SSO1318 did not hybridize. Total genomic DNA was extracted from the infected tissue sections for polymerase chain reaction (PCR) amplifica- tion of the haplosporidian. PCR amplifications with H. nelsoni-specific primers and with 'universal' actin primers did not yield the expected products of 573 and 700 bp, respectively. A series of primers was designed to amplify short regions of small subunit ribosomal DNA (SSU rDNA) from most haplo- sporidians. The primers encompass a highly variable region of the SSU rDNA and did not amplify oyster DNA. PCR amplification of the infected C. gigas genomic DNA with these primers yielded the expected-sized product from the primer pair targeting the shortest region (94 bp). This PCR product was sequenced and it was identical to the corresponding SSU rDNA region of H. nelsoni.
Standish K. Allen - One of the best experts on this subject based on the ideXlab platform.
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A field test investigating the influence of brood stock origin and ploidy on the susceptibility of Crassostrea virginica to “triploid mortality” in the Chesapeake Bay
Aquaculture, 2020Co-Authors: Joseph L. Matt, Eric Guévélou, Jessica Moss Small, Standish K. AllenAbstract:Abstract Mass mortalities of cultured triploid Crassostrea virginica in late spring, or “triploid mortality,” have been reported on farms in the Chesapeake Bay since 2012. Typical causes, such as disease or poor husbandry, were not responsible, and mortalities occurred without clear signs of biological or physical stressors. Previous comparisons of the effects of genetic origin on triploid mortality have been uncontrolled, initiating this investigation of the effect of brood stock source and ploidy on triploid mortality. Four triploid and four diploid crosses, produced by crossing different combinations of brood stock of Virginia, Louisiana, and Maine origin in early 2015, were tested at four commercial oyster farms in Virginia throughout 2016. From February to November, oysters from all crosses and sites were regularly sampled, and growth (shell height), condition (meat weight), and pathology were monitored, as were environmental conditions. Compared to diploids made from Virginia brood stock, diploids with Maine genetic origin had high mortality and Virginia-Maine diploid hybrids exhibited mid-parent heterosis. A triploid mortality event occurred in late spring at only one site and only affected the triploid crosses. Evidence for substantial disease pressure from Haplosporidium nelsoni or Perkinsus marinus or of especially stressful environmental conditions based on temperature, salinity, pH, and dissolved oxygen was absent during the triploid mortality event. At 18 months, shell height was similar in the diploids and triploids with the most similar genetic origin. Triploids maintained meat weight through the summer, while meat weight in diploids dropped sharply. Triploids may be especially susceptible to late spring mortality events in the Chesapeake Bay, which justifies their classification as “triploid mortality,” and warrants further investigation on traits in triploids that may affect susceptibility.
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Performance of selectively-bred lines of eastern oyster, Crassostrea virginica, across eastern US estuaries
Aquaculture, 2016Co-Authors: Dina A. Proestou, Standish K. Allen, Bryan T. Vinyard, Ryan J. Corbett, Jessica Piesz, Jessica M. Small, 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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Genetic improvement for disease resistance in oysters: A review.
Journal of Invertebrate Pathology, 2015Co-Authors: Lionel Dégremont, Celine Garcia, Standish K. AllenAbstract:Oyster species suffer from numerous disease outbreaks, often causing high mortality. Because the environment cannot be controlled, genetic improvement for disease resistance to pathogens is an attractive option to reduce their impact on oyster production. We review the literature on selective breeding programs for disease resistance in oyster species, and the impact of triploidy on such resistance. Significant response to selection to improve disease resistance was observed in all studies after two to four generations of selection for Haplosporidium nelsoni and Roseovarius crassostrea in Crassostrea virginica, OsHV-1 in Crassostrea gigas, and Martelia sydneyi in Saccostrea glomerata. Clearly, resistance in these cases was heritable, but most of the studies failed to provide estimates for heritability or genetic correlations with other traits, e.g., between resistance to one disease and another. Generally, it seems breeding for higher resistance to one disease does not confer higher resistance or susceptibility to another disease. For disease resistance in triploid oysters, several studies showed that triploidy confers neither advantage nor disadvantage in survival, e.g., OsHV-1 resistance in C. gigas. Other studies showed higher disease resistance of triploids over diploid as observed in C. virginica and S. glomerata. One indirect mechanism for triploids to avoid disease was to grow faster, thus limiting the span of time when oysters might be exposed to disease.
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breeding and domestication of eastern oyster crassostrea virginica lines for culture in the mid atlantic usa line development and mass selection for disease resistance
Journal of Shellfish Research, 2014Co-Authors: Anu Franklawale, Lionel Dégremont, Standish K. AllenAbstract:A selective breeding program for Crassostrea virginica was established in 1997 as part of an initiative in Virginia to address declining oyster harvests caused by the two oyster pathogens Haplosporidium nelsoni (MSX) and Perkinsus marinus (Dermo). Housed in the Aquaculture Genetics and Breeding Technology Center (ABC), the objective of the program was to develop and disseminate disease-resistant lines that would enable an oyster culture industry. Today, culture of disease-resistant cultivars accounts for more than 90% of oyster production in the state, where 28.1 million half-shell oysters and 2 billion eyed larvae were sold in 2012. Results of our line development program as of 2006 are reported. Eight ABC lines from 3 genetic groups—East Coast (EC), Louisiana (LA), and hybrids between the 2 (HY)—and 1 wild control line, were produced and tested. These 9 groups were deployed in 4 replicates across 4 Virginia sites characterized by low (Kinsale (KIN)), medium (York River (YRK) and Lynnhaven (LYN)), and high (Wachapreague (WAC)) salinity regimes. Groups were sampled routinely for survival, growth, and disease diagnosis between November 2004 and December 2006. At KIN, where salinity was low and below the threshold for MSX and Dermo, survival was 41%-46% greater than survival at the other 3 sites by the end of the trial. Where the diseases were present (LYN, YRK, and WAC), ABC lines in general had greater survival than the control, but this varied by genetic group. The EC groups had 52%- 82% greater survival, the HY groups had as much as 40% greater survival, and the LA groups performed worse than the control. Poor performance of the LA groups was a result of their susceptibility to MSX, and the majority of them died before the end of the study. The genetic effects varied with site, and the rank of the lines was inconsistent, such that the best line in one site was, in some cases, one of the worst in another. Genotype-by-environment interaction is clearly driven by disease and salinity. Growth was also influenced by site, genetic group, and an interaction between them. Compared with the wild control, ABC lines were 31%, 20%, 42%, and 24% heavier at the end of the trial in the KIN, YRK, LYN, and WAC sites, respectively. However, unlike survival, the best performers were those from the LA and HY groups. Again, line rankings changed across sites. For this reason, a salinity-specific breeding strategy to develop lines that perform optimally within a salinity range has been adopted.
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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, Celine Garcia, Anu Frank-lawale, 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...
Sheila A Kanaley - One of the best experts on this subject based on the ideXlab platform.
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in vitro interactions between bivalve hemocytes and the oyster pathogen Haplosporidium nelsoni msx
Journal of Parasitology, 1993Co-Authors: Susan E. Ford, Kathryn A Ashtonalcox, Sheila A KanaleyAbstract:Resistance to disease caused by the oyster pathogen Haplosporidium nelsoni (MSX) has developed in nature and through selective breeding; however, examination of tissue slides shows no evidence that phagocytic cells are involved. To investigate this phenomenon further, we quantified in vitro phagocytosis of plasmodial stages of H. nelsoni by hemocytes from 2 oyster and 1 mussel species. Our results show that hemocytes from oysters Crassostrea virginica, whether selected or unselected for resistance to MSX disease, did not ingest plasmodia unless the parasites were damaged or killed. Time-lapse photography suggested that granular hemocytes retreated rapidly after initial contact with living plasmodia and thatnearby agranular hemocytes showed little movement
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cellular responses of oysters infected with Haplosporidium nelsoni changes in circulating and tissue infiltrating hemocytes
Journal of Invertebrate Pathology, 1993Co-Authors: Susan E. Ford, Sheila A Kanaley, D T J LittlewoodAbstract:The protozoan parasite Haplosporidium nelsoni (MSX) elicits an inflammatory-type response in oysters, Crassostrea virginica. We assayed circulating hemocytes of oysters exposed to H. nelsoni to quantify the effects of parasitism, selection for resistance, and season on total and differential counts. All factors had a significant (P selection (4%) > infection (2%)]. Circulating hemocyte densities increased with infection intensity in resistant animals, but were depressed in susceptible oysters with light infections. Counts in both groups were lowest in August and highest in May, at which times densities in susceptible oysters were reduced (P 0.05) association with numbers of circulating hemocytes in individual oysters. Size-frequency analysis with a Coulter counter indicated that the proportion of large cells (presumed to be granular hemocytes) was lower (P < 0.0001) in susceptible oysters, which were also heavily infected, compared to resistant oysters, which had very few infections. The loss of granular hemocytes may stem from degranulation associated with tissue damage and inflammation. Present evidence suggests that the principal role of the hemocyte response in MSX disease is to plug lesions, remove debris, and repair tissues and that these functions may help oysters survive infection.
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evidence for regular sporulation by Haplosporidium nelsoni msx ascetospora haplosporidiidae in spat of the american oyster crassostrea virginica
Journal of Eukaryotic Microbiology, 1991Co-Authors: Robert D. Barber, Sheila A Kanaley, Susan E. FordAbstract:: The spore stage of Haplosporidium nelsoni, the ascetosporan parasite causing multinucleated sphere unknown (MSX) disease in oysters, Crassostrea virginica, has been reported so rarely (less than 0.01% of infected oysters) that a second host has been postulated. However, recent intensive sampling of young (less than 1 year) oysters in Delaware Bay, U.S. suggests that spore formation occurs regularly in this group and that spores are produced in at least 75-85% of all infections reaching the advanced stage. Sporulation was seasonal, occurring over two to three weeks in late June/early July and again in late summer/early fall. Our data indicate that sporulation by H. nelsoni in oysters is more common than previously suspected, occurring in a segment of the host population that may not have been sufficiently sampled in the past, and that a direct life cycle should be reconsidered.
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panning a technique for enrichment of the oyster parasite Haplosporidium nelsoni msx
Journal of Invertebrate Pathology, 1990Co-Authors: Susan E. Ford, Sheila A Kanaley, Michael Ferris, Kathryn A AshtonalcoxAbstract:Abstract Plasmodial stages of the parasite Haplosporidium nelsoni (MSX) were enriched an average eight-fold with recovery of 60 to 80% using a process known as “panning” of hemolymph from infected oysters (Crassostrea virginica). The method takes advantage of the greater adherence of hemocytes, compared to parasites, to inert surfaces. Hemolymph from infected oysters was layered onto a Petri dish and cells were allowed to settle for 30 min. Nonadhering cells were gently washed, decanted, and placed in a second Petri dish. Maximum enrichment and recovery of parasites were obtained after three panning cycles. Viability, estimated by trypan blue dye exclusion, was greater than 95%. Parasite-to-hemocyte ratios before panning were highly correlated to those after panning, but correlation decreased with each incubation. Initial concentration of parasites, which ranged from 1.4 to 5 × 105/ml, was also significantly correlated with the percentage recovery. We suggest that other extracellular invertebrate protozoans may also be enriched by the same method, which is much simpler, gentler, and less expensive than most other cell separation procedures.
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lectin binding characteristics of haemocytes and parasites in the oyster crassostrea virginica infected with Haplosporidium nelsoni msx
Parasite Immunology, 1990Co-Authors: Sheila A Kanaley, Susan E. FordAbstract:: Lectin-binding surface receptors on haemocytes from host oysters were compared with those on plasmodial stages of the ascetosporan parasite Haplosporidium nelsoni (MSX). Haemocytes were agglutinated, in descending order of strength, by WGA, HPA, LPA, ConA, and CFA. GMA, PHA, and RMA lectins failed to agglutinate at 100 micrograms/ml, the highest concentration tested. These results indicate that haemocytes contain surface receptors resembling N-acetyl-D-glucosamine and alpha-methylmannopyranoside. Fluorescent (FITC) labelled ConA and WGA also bound to H. nelsoni plasmodia, but parasites were commonly excluded from clumps of agglutinated haemocytes, except for those that were apparently trapped passively in large aggregates. Although seasonal variations existed, agglutination titres for all reacting lectins were 2- to 8-fold higher for cells from systemically infected oysters compared to control oysters not manifesting systemic infections. Preincubation of lectins in serum from control animals reduced agglutination titres 6- to 9-fold, whereas incubation in serum from systemically infected oysters reduced titres only 4- to 6-fold. The loss of lectin-like molecules from the serum of systemically infected animals, and the concurrent increase of lectin receptors in the haemocytes population, is probably related to known changes in haemocytes composition and the loss of serum glycoproteins in diseased animals. Antigenic similarities were detected between surface receptors on oyster haemocytes and those on H. nelsoni plasmodia, which may help explain the failure of oyster haemocytes to phagocytose this parasite.
