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

Multiple Fundamental Frequency Pitch Detection for Real Time MIDI Applications

This study aimed to develop a real time multiple fundamental frequency detection algorithm for real time pitch to MIDI conversion applications. The algorithm described here uses neural network classifiers to make classifications in order to define a chord pattern (combination of multiple fundamental frequencies). The first classification uses a binary decision tree that determines the root note (first note) in a combination of notes; this is achieved through a neural network binary classifier. For each leaf of the binary tree, each classifier determines the frequency group of the root note (low or high frequency) until only two frequencies are left to choose from. The second classifier determines the amount of polyphony, or number of notes played. This classifier is designed in the same fashion as the first, using a binary tree made up of neural network classifiers. The third classifier classifies the chord pattern that has been played. The chord classifier is chosen based on the root note and amount of polyphony, the first two classifiers constrain the third classifier to chords containing only a specific root not and a set polyphony. This allows for the classifier to be more focused and of a higher accuracy. To further increase accuracy, an error correction scheme was devised based on repetitive coding, a technique that holds out multiple frames and compares them in order to detect and correct errors. Repetitive coding significantly increases the classifiers accuracy; it was found that holding out three frames was suitable for real-time operation in terms of throughput, though holding out more frames further increases accuracy it was not suitable real time operation. The algorithm was tested on a common embedded platform, which through benchmarking showed the algorithm was well suited for real time operation

Nurses\u27 Alumnae Association Bulletin - Volume 2 Number 1

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Does natural selection explain the fine scale genetic structure at the nuclear exon Glu-5 ' in blue mussels from Kerguelen ?

The Kerguelen archipelago, isolated in the Southern Ocean, shelters a blue mussel Mytilus metapopulation far from any influence of continental populations or any known hybrid zone. The finely carved coast leads to a highly heterogeneous habitat. We investigated the impact of the environment on the genetic structure in those Kerguelen blue mussels by relating allele frequencies to habitat descriptors. A total sample comprising up to 2248 individuals from 35 locations was characterized using two nuclear markers, mac-1 and Glu-5, and a mitochondrial marker (COI). The frequency data from 9 allozyme loci in 9 of these locations were also reanalyzed. Two other nuclear markers (EFbis and EFprem's) were monomorphic. Compared to Northern Hemisphere populations, polymorphism in Kerguelen blue mussels was lower for all markers except for the exon Glu-5. At Glu-5, genetic differences were observed between samples from distinct regions (F-CT=0.077), as well as within two regions, including between samples separated by <500m. No significant differentiation was observed in the AMOVA analyses at the two other markers (mac-1 and COI). Like mac-1, all allozyme loci genotyped in a previous publication, displayed lower differentiation (Jost's D) and F-ST values than Glu-5. Power simulations and confidence intervals support that Glu-5 displays significantly higher differentiation than the other loci (except a single allozyme for which confidence intervals overlap). AMOVA analyses revealed significant effects of the giant kelp Macrocystis and wave exposure on this marker. We discuss the influence of hydrological conditions on the genetic differentiation among regions. In marine organisms with high fecundity and high dispersal potential, gene flow tends to erase differentiation, but this study showed significant differentiation at very small distance. This may be explained by the particular hydrology and the carved coastline of the Kerguelen archipelago, together with spatially variable selection at Glu-5

Mitochondrial gene variation in Mercenaria clam sibling species reveals a relict secondary contact zone in the western Gulf of Mexico

We investigated phylogeographic relationships among American Mercenaria taxa by assessing variation in a 444 nucleotide fragment of the mitochondrial 16S ribosomal gene in clams sampled from four representative sites in January to November 1994. Three of these sites were in the Gulf of Mexico, one was on the Atlantic coast in South Carolina. Direct sequencing of this amplified gene fragment in 85 individuals revealed 21 haplotypes. Phylogenetic analyses consistently resolved this variation into three well supported clades, and within-clade genetic divergence levels were markedly lower than among-clade values. One of the clades, A, was taxon-specific, in that it solely and exclusively contained specimens of M. mercenaria (Linnaeus, 1758) sampled in South Carolina. The other two clades, B and C, were the most divergent and both encompassed specimens of M. campechiensis (Gmelin, 1791) and of M. campechiensis texana (Dall, 1902), sampled from the three Gulf of Mexico sites. Clade B was found at high frequencies at all three Gulf sites, whereas Clade C occurred at low frequencies at two western Gulf sites. We interpret this pattern as resulting from the secondary contact and introgression of two allopatrically differentiated Mercenaria taxa in the western Gulf of Mexico. Clade C haplotypes may represent relict mitochondrial lineages from original Gulf Mercenaria spp. populations that predate massive mitochondrial introgression by M. campechiensis . We further propose that the M. campechiensis texana nuclear genome is a mosaic, heavily weighted toward M. campechiensis , but containing some relict alleles inherited from the precontact population, especially those governing shell characteristics, which may be adaptive in cohesive sediments of bays and estuaries in the northwestern Gulf of Mexico.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46625/1/227_2004_Article_BF00351334.pd

Mitochondrial cytochrome oxidase I gene sequences support an Asian origin for the Portuguese oyster Crassostrea angulata

The Portuguese oyster Crassostrea angulata (Lamarck, 1819) was long assumed to be native to the northeastern Atlantic, however, a number of lines of evidence now indicate that it is a close relative, or identical, to the Asian Pacific oyster C. gigas (Thunberg, 1793). Three hypotheses have been proposed to explain how this strikingly disjunct geographic distribution may have come about: ancient vicariance events, recent anthropogenic introduction to Asia and recent anthropogenic introduction to Europe. We have performed a molecular phylogenetic analysis of C. angulata based on mitochondrial DNA sequence data for a 579-nucleotide fragment of cytochrome oxidase I. Our results show that Portuguese oyster haplotypes cluster robustly within a clade of Asian congeners and are closely related, but not identical, to C. gigas from Japan. The mitochondrial data are the first to show that Portuguese oysters are genetically distinct from geographically representative samples of Japanese Pacific oysters. Our phylogenetic analyses are consistent with a recent introduction of C. angulata to Europe either from a non-Japanese Asian source population or from a subsequently displaced Japanese source population. Genetic characterization of Pacific oysters throughout their Asian range is necessary to fully reveal the phylogenetic relationships among Portuguese and Pacific oysters.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42028/1/227-131-3-497_81310497.pd

Stress related epigenetic changes may explain opportunistic success in biological invasions in Antipode mussels

Different environmental factors could induce epigenetic changes, which are likely involved in the biological invasion process. Some of these factors are driven by humans as, for example, the pollution and deliberate or accidental introductions and others are due to natural conditions such as salinity. In this study, we have analysed the relationship between different stress factors: time in the new location, pollution and salinity with the methylation changes that could be involved in the invasive species tolerance to new environments. For this purpose, we have analysed two different mussels’ species, reciprocally introduced in antipode areas: the Mediterranean blue mussel Mytilus galloprovincialis and the New Zealand pygmy mussel Xenostrobus securis, widely recognized invaders outside their native distribution ranges. The demetylathion was higher in more stressed population, supporting the idea of epigenetic is involved in plasticity process. These results can open a new management protocols, using the epigenetic signals as potential pollution monitoring tool. We could use these epigenetic marks to recognise the invasive status in a population and determine potential biopollutants

Differential immunity as a factor influencing mussel hybrid zone structure

Interspecific hybridisation can alter fitness-related traits, including the response to pathogens, yet immunity is rarely investigated as a potential driver of hybrid zone dynamics, particularly in invertebrates. We investigated the immune response of mussels from a sympatric population at Croyde Bay, within the hybrid zone of Mytilus edulis and Mytilus galloprovincialis in Southwest England. The site is characterised by size-dependent variation in genotype frequencies, with a higher frequency of M. galloprovincialis alleles in large mussels, largely attributed to selective mortality in favour of the M. galloprovincialis genotype. To determine if differences in immune response may contribute to this size-dependent variation in genotype frequencies, we assessed the two pure species and their hybrids in their phagocytic abilities when subject to immune challenge as a measure of immunocompetence and measured the metabolic cost of mounting an antigen-stimulated immune response. Mussels identified as M. galloprovincialis had a greater immunocompetence response at a lower metabolic cost compared to mussels identified as M. edulis. Mussels identified as hybrids had intermediate values for both parameters, providing no evidence for heterosis but suggesting that increased susceptibility compared to M. galloprovincialis may be attributed to the M. edulis genotype. The results indicate phenotypic differences in the face of pathogenic infection, which may be a contributing factor to the differential mortality in favour of M. galloprovincialis, and the size-dependent variation in genotype frequencies associated with this contact zone. We propose that immunity may contribute to European mussel hybrid zone dynamics