Repeatability of the enrichment procedure for triploid C. ariakensis larvae

The principal concern for an industry based on aquaculture of triploid C. ariakensis is biosecurity, that is, the assurance against unwanted introduction of the species into the Bay during aquaculture practices. Essentially, this boils down to keeping as many diploids as possible out of the trip lo id population. We set about addressing some questions concerning reducing or eliminating the number of diploids (which on average occur at a rate of 0.1 %). • Can diploids be purged from 4n x 2n batches by size grading? • Is there a difference in the number of diploids eliminated between first and last harvests of eyed larvae? • Can we quantify the degree to which we have purified the triploids

Hybridization Of Tetraploid And Diploid Crassostrea Gigas (Thunberg) With Diploid C-Ariakensis (Fujita)

Three replicates of hybrid crosses of tetraploid and diploid C gigas (Thunberg) with diploid C ariakensis (Fujita) were produced with controls. Larval survival and growth were documented. Cytological events were also monitored in oocytes from hybrid crosses following insemination. Among the four types of hybrid crosses, diploid C. gigas (female) x diploid C. ariakensis (male) (GA) was the most successful. Survival of GA was about the same as that of controls in two of three replications, although its growth rate was 25-30% lower. Crosses of tetraploid C. gigas (female) and diploid C. ariakensis (male) (GGA) had poor yield at day 2 post-fertilization (0.05%), but grew nearly as well as controls subsequently. The other two types of hybrids (i.e., diploid C. ariakensis [female] and tetraploid C. gigas [male] [AGG], diploid C ariakensis [female] and diploid C. gigos [male] [AG]) suffered very low yield at day 2 (0.01% and 0.003%) and grew very slowly. Spat were obtained from all replicates of GA crosses and one of three replicates of GGA, and proved to be hybrids by polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) diagnosis. GGA hybrids were confirmed to be triploid by flow cytometry. No larvae survived to eyed stage in AGG or AG crosses. Cytological examination revealed that the vast majority (\u3e99%) of oocytes from hybrid crosses had a prolonged meiotic prophase I or metaphase I at least through 180 min post-insemination

Evaluation of cytochalasin B and 6-dimethylaminopurine for tetraploidy induction in the Eastern oyster, Crassostrea virginica

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, ornine-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. (C) 2015 Elsevier B.V. All rights reserved

Aquaculture genomics, genetics and breeding in the United States: current status, challenges, and priorities for future research

Advancing the production efficiency and profitability of aquaculture is dependent upon the ability to utilize a diverse array of genetic resources. The ultimate goals of aquaculture genomics, genetics and breeding research are to enhance aquaculture production efficiency, sustainability, product quality, and profitability in support of the commercial sector and for the benefit of consumers. In order to achieve these goals, it is important to understand the genomic structure and organization of aquaculture species, and their genomic and phenomic variations, as well as the genetic basis of traits and their interrelationships. In addition, it is also important to understand the mechanisms of regulation and evolutionary conservation at the levels of genome, transcriptome, proteome, epigenome, and systems biology. With genomic information and information between the genomes and phenomes, technologies for marker/causal mutation-assisted selection, genome selection, and genome editing can be developed for applications in aquaculture. A set of genomic tools and resources must be made available including reference genome sequences and their annotations (including coding and non-coding regulatory elements), genome-wide polymorphic markers, efficient genotyping platforms, high-density and high-resolution linkage maps, and transcriptome resources including non-coding transcripts. Genomic and genetic control of important performance and production traits, such as disease resistance, feed conversion efficiency, growth rate, processing yield, behaviour, reproductive characteristics, and tolerance to environmental stressors like low dissolved oxygen, high or low water temperature and salinity, must be understood. QTL need to be identified, validated across strains, lines and populations, and their mechanisms of control understood. Causal gene(s) need to be identified. Genetic and epigenetic regulation of important aquaculture traits need to be determined, and technologies for marker-assisted selection, causal gene/mutation-assisted selection, genome selection, and genome editing using CRISPR and other technologies must be developed, demonstrated with applicability, and application to aquaculture industries. Major progress has been made in aquaculture genomics for dozens of fish and shellfish species including the development of genetic linkage maps, physical maps, microarrays, single nucleotide polymorphism (SNP) arrays, transcriptome databases and various stages of genome reference sequences. This paper provides a general review of the current status, challenges and future research needs of aquaculture genomics, genetics, and breeding, with a focus on major aquaculture species in the United States: catfish, rainbow trout, Atlantic salmon, tilapia, striped bass, oysters, and shrimp. While the overall research priorities and the practical goals are similar across various aquaculture species, the current status in each species should dictate the next priority areas within the species. This paper is an output of the USDA Workshop for Aquaculture Genomics, Genetics, and Breeding held in late March 2016 in Auburn, Alabama, with participants from all parts of the United States

Genetic Considerations for Hatchery-Based Restoration of Oyster Reefs : A summary from the September 21-22, 2000 workshop

The following is a summary of issues and considerations surrounding the use of hatchery stocks for restoration of public oyster reefs. This summary stems from a workshop conducted at the Virginia Institute of Marine Science (VIMS). The original goal of the workshop was to try to develop a consensus, or at least a general agreement, on genetic policy(ies) for stocking oyster reefs. To do this, the first day of the workshop was devoted to placing the genetic concerns on the table in the context of both Maryland and Virginia oyster replenishment and restoration programs. The conclusions from the first day of presentations revealed that there are a number of scenarios for hatchery-based restoration/ replenishment and that the genetic considerations varied among them. Other genetic considerations were common to the whole Bay. This document summarizes a great deal of discussion, and consequently some detail is omitted

The Effect Of Cytochalasin B Dosage On The Survival And Ploidy Of Crassostrea Virginica (Gmelin) Larvae

Survival and ploidy of D-stage oyster larvae (Crassostrea virginica) were determined following the rearing of embryos exposed to CB dosages of 0.5 mg/L, 0.25 mg/L, and 0.125 mg/L for 10 minutes, with 0.05% DMSO and ambient seawater as controls. The experiment was replicated three times on the same day with the same procedures and partially stripping the same male oysters; different females were used for each replicate. CB dosage treatments began when 50% of the eggs reached PBI (24-31 min). Embryos were reared for 48 h at ambient temperature and salinity. Resulting triploid percentages were 13% +/- 6.7% (0.125 mgCB/L), 61.8% +/- 6.2% (0.75 mgCB/L). and 68.2% +/- 14.1% (0.5 mgCB/L). No significant difference (P less than or equal to 0.05) in mean survival was found between the three CB treatments. Significant differences in mean survival between the three replicates implies variability because of different sources of eggs

Improving Production of the Eastern Oyster Crassostrea virginica through Coordination of Genetic Improvement Programs, Research, and Technology Transfer Activities

The East Coast Shellfish Growers Association has been actively advocating for continued improvement of breeding infrastructure to support a vibrant and ecologically crucial industry. This white paper acknowledges these efforts and is meant to serve as a paradigm for oyster breeding on the East Coast. The vision is relatively straightforward; however, its execution—like most things—will be fraught with detail and inertia. Yet describing simply the idea without articulating some detail and potential roadblocks would be misleading. Instead, we present a picture of a breeding paradigm as it might play out across the entire range of a species. At this particular time, when there is increasing interest in oyster aquaculture and the breeding that supports it, and with incipient programs emerging in the Northeast and Gulf, this ‘‘plea’’ for a common approach is meant to help unify shellfish breeding

Breeding And Domestication Of Eastern Oyster (Crassostrea Virginica) Lines For Culture In The Mid-Atlantic, Usa: Line Development And Mass Selection For Disease Resistance

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 Perkinsusmarinus (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