Selection for Enhanced Disease Resistance and Growth Performance in Cross-bred Eastern Oysters, \u3ci\u3eCrassostrea virginica\u3c/i\u3e

Through a replicated field trial we will test the hypothesis that enhanced disease resistance to multiple diseases and improved growth can be realized through a combination of interline crossing and genetic selection on cross-bred lines of oysters. Together with oyster growers, hatchery operators and extension agents, we will develop guidelines and protocols for the transfer of the best performing lines from our program to commercial hatcheries and the industry. Project results and updates on access to broodstock will be presented at the annual NACE meeting, at annual meetings of the National Shellfisheries Association and via a Fact Sheet at the project’s end

CAREER: Physiological Genetics of the Dwarf Surf Clam, Mulinia lateralis

Heterosis, or hybrid vigor, is a condition where more heterozygous individuals physiologically outperform more homozygous individuals. Although heterosis has often been reported for marine bivalves, as well as other taxa, the physiological and genetic bases of heterosis are still poorly understood. The proposed research will use a combination of quantitative and molecular genetic approaches to examine the physiological and genetic underpinnings of heterosis in the dwarf surf clam, Mulinia lateralis. The specific goals of this work are: 1) to determine the genetic and physiological basis of growth rate variation, 2) to estimate the degree to which the physiological components of growth are genetically correlated, 3) to determine whether levels of heterozygosity are significantly associated with physiological performance under both stressful and non-stressful conditions, and 4) to determine the importance of inbreeding to any association between heterozygosity and physiological performance in M. lateralis. Three separate educational activities will be integrated with these research goals. First, M. lateralis will be used as a teaching model for a laboratory section to accompany the graduate level course in quantitative genetics currently taught at the University of Maine. Second, an internship will be established that will enable high school teachers and students to directly participate in the proposed research and gain hands-on training in molecular biology, bivalve husbandry, and quantitative genetics. Third, a summer content institute in genetics for secondary science teachers will be developed. This institute is intended to help teachers keep pace with the rapid advances in genetic research and effectively communicate these advances to their students. Along with the summer genetics institute, a series of pilot projects will be established in local schools exploring the most effective way to use M. lateralis as a model for demonstrating bivalve physiology, ecology, and genetics in a manner consistent with state and national standards

Collaborative Research: Extreme Discordance between Allozyme and Non-allozyme Introgression in Baltic Mussels. Selection on Allozymes?

A major challenge for evolutionary biologists is to determine the degree to which natural selection shapes genetic variation in natural populations. Hybridization is common between two species of blue mussel found in the North and Baltic Seas. The differential exchange of genes between the two mussel species, particularly genes encoding enzymes involved in central metabolic pathways, suggests those genes may be under selection and involved in adaptation to low salinity conditions in the Baltic Sea. Tests for selection will be conducted by comparing levels of genetic exchange for these metabolic genes against nonmetabolic and presumably neutral (i.e., not under selection) genes and by looking for signals of selection at the DNA sequence level. This project will further the understanding of how natural selection operates at multiple genes, especially at the boundaries between hybridizing species. It will also enhance educational opportunities in population biology and evolutionary ecology for women and minorities and contribute to the development of K-12 educational outreach materials in these fields

Linking Bioturbation and Sensory Biology: Chemoreception Mechanisms in Deposit-Feeding Polychaetes

Soft-sediment benthic habitats are ubiquitous in the marine environment and typically feature macrofaunal assemblages that include large numbers of deposit-feeding invertebrates such as polychaetes, bivalves, gastropods, crustaceans, holothurians, and hemichordates. Via their feeding, modulated in part by chemoreception, these organisms have profound effects on the ecology, biology, geology, and chemistry of their habitats. Very little is known, however, concerning the physiology and molecular biology of chemoreception in deposit feeders. This research is a comprehensive investigation of the sensory mechanisms coordinating chemoreception in deposit feeding spionid polychaetes. It directly addresses this lack of information and will therefore have a significant impact on the current understanding of chemoreception in polychaetes and other marine invertebrates. In the first of three objectives, the ultrastructure and innervation of putative sensory structures on spionid polychaete palps will be described using electron and confocal microscopy. Second, the chemoreceptive capacity of palp sensory cells and nuchal organs will be tested with behavioral assays and activity-dependent cell labeling studies. The behavioral assays will identify chemical cues that elicit significant feeding responses and establish their threshold sensitivities. Complementary immunocytochemistry experiments will determine (1) if the chemicals that elicit behavioral responses activate the sensory cells described in objective 1; (2) the sensitivity of the sensory cells (i.e., stimulation thresholds); and (3) the distribution of cells responding to a particular chemical cue. Third, a functional biochemical approach will be used to characterize and isolate candidate chemoreceptor proteins associated with the peripheral sensory cells and nuchal organs. Several outcomes of the research are of particular significance. First, the cell-labeling method will be further refined for use with small invertebrates, and will provide a powerful tool for future studies of the neural mechanisms coordinating habitat selection by many species of marine invertebrate larvae. Second, the sequence information and purified receptor will set the stage for development of mRNA and antibody probes that can be used to examine gene expression and detail the chemosensory transduction pathways in polychaetes and other marine invertebrates. Such information will be useful to researchers interested in the evolutionary relationships among invertebrate phyla and the in evolution of sensory structures. In addition to its scientific relevance, the project provides significant opportunities for graduate and undergraduate student training. Three K-12 educators or high school students will also participate through the Maine Research Internships for Teachers and Students program. Their participation not only increases the capacity of this over subscribed program, but also strengthens the links between the local K-12 community and the University of Maine. Internet activities and resources will be created that focus on sensory perception and ecology in the marine environment. These materials will extend the research to an even larger Internet audience and facilitate the incorporation of ocean science examples into topics typically approached only from a terrestrial and human perspective

Collaborative Research: Determinants of male reproductive success in natural spawns

This proposal is an extension of previous work aimed at understanding the effects of reproductive biology on patterns of life history evolution in a colonial marine tunicate, Botryllus schlosseri. The project will test five hypotheses about factors that may determine male reproductive success in natural spawns of this colonial invertebrate. The five hypotheses specifically aim to explore the effects of timing of sperm release, relatedness of mates, population density, and allocation to male function on fertilization success in field and experimental populations of Botryllus. Previous work has shown that there is a narrow temporal window in which fertilization can result in a viable embryo, and there may be a gametic incompatibility system. Furthermore, fertilizing sperm are generally the product of nearby colonies; colonies exhibit variation in sperm production, and high levels of sperm production only increase local reproductive success when sperm competition occurs.This preliminary information suggests that male reproductive success in natural populations is a complex function of timing relative to the reproductive cycles of other colonies, gametic compatibility, sperm production, and population density.The proposed research will consist of field and laboratory studies, with preliminary work focused to maximize the information yield of a suite of nine polymorphic microsatellite loci. These genetic markers will then be used to assay paternity in natural spawns and test the series of five hypotheses about the determinants of male reproductive success

Mud Blister Worms and Oyster Aquaculture

The mud blister worm, Polydora websteri Hartman (Loosanoff and Engle 1943), burrows into the shells of bivalve mollusks, including Eastern oysters (Crassostrea virginica), sea scallops (Placopecten magellanicus) and blue mussels (Mytilus edulis). This report is for oyster producers interested in controlling mud blister worms, which when present in large numbers can reduce the value of oysters sold to the half-shell market. Although other species of blister-causing worms occur in several genera including Polydora, Pseudopolydora, and Boccardia, this report focuses specifically on Polydora websteri

Neural Networks and the Classification of Active Galactic Nucleus Spectra

The use of Artificial Neural Networks (ANNs) as a classifier of digital spectra is investigated. Using both simulated and real data, it is shown that neural networks can be trained to discriminate between the spectra of different classes of active galactic nucleus (AGN) with realistic sample sizes and signal-to-noise ratios. By working in the Fourier domain, neural nets can classify objects without knowledge of their redshifts.Comment: 11 pages, LaTeX, including two postscript figures, 41 kb. Accepted for publication in Publ. AS

Experimental Determination of Salinity, Temperature, Growth, and Metabolic Effects on Shell Isotope Chemistry of Mytilus Edulis Collected from Maine and Greenland

To study the effects of temperature, salinity, and life processes (growth rates, size, metabolic effects, and physiological/ genetic effects) on newly precipitated bivalve carbonate, we quantified shell isotopic chemistry of adult and juvenile animals of the intertidal bivalve Mytilus edulis (Blue mussel) collected alive from western Greenland and the central Gulf of Maine and cultured them under controlled conditions. Data for juvenile and adult M. edulis bivalves cultured in this study, and previously by Wanamaker et al. (2006), yielded statistically identical paleotemperature relationships. On the basis of these experiments we have developed a species-specific paleotemperature equation for the bivalve M. edulis [T degrees C = 16.28 (+/- 0.10) -4.57 (+/- 0.15) {delta(18)O(c) VPBD - delta(18)O(w) VSMOW} + 0.06 (+/- 0.06) {delta(18)O(c) VPBD - delta(18)O(w) VSMOW}(2); r(2) = 0.99; N = 323; p \u3c 0.0001]. Compared to the Kim and O\u27Neil (1997) inorganic calcite equation, M. edulis deposits its shell in isotope equilibrium (delta(18)O(calcite)) with ambient water. Carbon isotopes (delta(13)C(calcite)) from sampled shells were substantially more negative than predicted values, indicating an uptake of metabolic carbon into shell carbonate, and delta(13)C(calcite) disequilibrium increased with increasing salinity. Sampled shells of M. edulis showed no significant trends in delta(18)O(calcite) based on size, cultured growth rates, or geographic collection location, suggesting that vital effects do not affect delta(18)O(calcite) in M. edulis. The broad modern and paleogeographic distribution of this bivalve, its abundance during the Holocene, and the lack of an intraspecies physiologic isotope effect demonstrated here make it an ideal nearshore paleoceanographic proxy throughout much of the North Atlantic Ocean

Experimental Determination of Salinity, Temperature, Growth, and Metabolic Effects on Shell Isotope Chemistry of Mytilus edulis Collected from Maine and Greenland

To study the effects of temperature, salinity, and life processes (growth rates, size, metabolic effects, and physiological/ genetic effects) on newly precipitated bivalve carbonate, we quantified shell isotopic chemistry of adult and juvenile animals of the intertidal bivalve Mytilus edulis (Blue mussel) collected alive from western Greenland and the central Gulf of Maine and cultured them under controlled conditions. Data for juvenile and adult M. edulis bivalves cultured in this study, and previously by Wanamaker et al. (2006), yielded statistically identical paleotemperature relationships. On the basis of these experiments we have developed a species-specific paleotemperature equation for the bivalve M. edulis [T degrees C = 16.28 (+/- 0.10) -4.57 (+/- 0.15) {delta(18)O(c) VPBD - delta(18)O(w) VSMOW} + 0.06 (+/- 0.06) {delta(18)O(c) VPBD - delta(18)O(w) VSMOW}(2); r(2) = 0.99; N = 323; p \u3c 0.0001]. Compared to the Kim and O\u27Neil (1997) inorganic calcite equation, M. edulis deposits its shell in isotope equilibrium (delta(18)O(calcite)) with ambient water. Carbon isotopes (delta(13)C(calcite)) from sampled shells were substantially more negative than predicted values, indicating an uptake of metabolic carbon into shell carbonate, and delta(13)C(calcite) disequilibrium increased with increasing salinity. Sampled shells of M. edulis showed no significant trends in delta(18)O(calcite) based on size, cultured growth rates, or geographic collection location, suggesting that vital effects do not affect delta(18)O(calcite) in M. edulis. The broad modern and paleogeographic distribution of this bivalve, its abundance during the Holocene, and the lack of an intraspecies physiologic isotope effect demonstrated here make it an ideal nearshore paleoceanographic proxy throughout much of the North Atlantic Ocean

The Effect of a Two-Stage Heat-Treatment on the Microstructural and Mechanical Properties of a Maraging Steel

Maraging steels gain many of their beneficial properties from heat treatments which induce the precipitation of intermetallic compounds. We consider here a two-stage heat-treatment, first involving austenitisation, followed by quenching to produce martensite and then an ageing treatment at a lower temperature to precipitation harden the martensite of a maraging steel. It is shown that with a suitable choice of the initial austenitisation temperature, the steel can be heat treated to produce enhanced toughness, strength and creep resistance. A combination of small angle neutron scattering, scanning electron microscopy, electron back-scattered diffraction, and atom probe tomography were used to relate the microstructural changes to mechanical properties. It is shown that such a combination of characterisation methods is necessary to quantify this complex alloy, and relate these microstructural changes to mechanical properties. It is concluded that a higher austenitisation temperature leads to a greater volume fraction of smaller Laves phase precipitates formed during ageing, which increase the strength and creep resistance but reduces toughness