Jacking in Chinook salmon (Oncorhynchus tshawytscha ): environmental and genotypic effects on life history strategy

Jacking in Chinook salmon (Oncorhynchus tshawytscha), is defined as precocious sexual maturation of males after at least 1 year in sea water, and occurring 1 year prior to females of the same cohort. Substantial evidence supports genetic, environmental, and genetic by environmental effects on precocious maturation in Chinook salmon, however the underlying mechanisms remain unclear. Passive integrated transponder tagged fish were followed through fresh and salt water growth to the sexual maturation of the jacks. Growth data was recorded to examine the relationship between size/growth effects in freshwater rearing on subsequent precocious sexual maturation of the jacks. No effect of size/growth in freshwater was detected. Reanalysis of data from a previous study showed an effect of developmental rate on jacking. Sequencing tested the possibility of a relationship between jacking and Major Histocompatibility (MH) genes at the MH class II β 1 locus. One genotype positively affected the likelihood of jacking

Vaccines for finfish aquaculture: What do we need to know to make them work?

Dixon, B. (2012). Vaccines for finfish aquaculture: What do we need to know to make them work? Electronic Journal of Biotechnology, 15(5). https://doi.org/10.2225/vol15-issue5-fulltext-18. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.Aquaculture still faces serious economic impacts due to the loss of animals to disease. A conservative estimate of 5% losses due to disease means that the finfish aquaculture industry loses over $1 billion annually on a global scale. One proven way to prevent costly disease outbreaks is to vaccinate fish against common or known pathogens. Current vaccination schemes still result in losses, however, and this may be due in part to vaccine design. Vaccines are currently designed using state of the art knowledge of immune responses, which is based primarily on mammalian studies. Just how applicable is this information to fish immunity and vaccine design, however? This review discusses what is currently known for teleost fish about two key processes that drive immune response: antigen presentation and cytokine regulation. In both cases many of the genes known to be involved have been identified; in the case of cytokines recent genome projects have added to the total rapidly in recent years. Most functional studies to date in these areas have focused on gene expression and mRNA levels, due to a lack of available antibodies that are required for studies at the protein level. These studies are confounded by the fact that in many cases the teleost equivalents of single copy mammalian genes are duplicated and are regulated in very different ways. This suggests that vaccines designed around mammalian immunological principles will not be as efficient as they could be. Future research goals for fish immunologists should be to develop the antibodies required for protein level functional studies in order to provide the true understanding of fish immunity that is required for the design of finfish aquaculture vaccines that are truly effective.Natural Sciences and Engineering Research Council of Discovery Grant number 217529-2008NSERC Canada Research Chair fellowship

The impact of sex-role reversal on the diversity of the major histocompatibility complex: Insights from the seahorse (Hippocampus abdominalis)

Background: Both natural and sexual selection are thought to influence genetic diversity, but the study of the relative importance of these two factors on ecologically-relevant traits has traditionally focused on species with conventional sex-roles, with male-male competition and female-based mate choice. With its high variability and significance in both immune function and olfactory-mediated mate choice, the major histocompatibility complex(MHC/MH) is an ideal system in which to evaluate the relative contributions of these two selective forces to genetic diversity. Intrasexual competition and mate choice are both reversed in sex-role reversed species, and sexrelated differences in the detection and use of MH-odor cues are expected to influence the intensity of sexual selection in such species. The seahorse, Hippocampus abdominalis, has an exceptionally highly developed form of male parental care, with female-female competition and male mate choice. Results: Here, we demonstrate that the sex-role reversed seahorse has a single MH class II beta-chain gene and that the diversity of the seahorse MHIIb locus and its pattern of variation are comparable to those detected in species with conventional sex roles. Despite the presence of only a single gene copy, intralocus MHIIb allelic diversity in this species exceeds that observed in species with multiple copies of this locus. The MHIIb locus of the seahorse exhibits a novel expression domain in the male brood pouch. Conclusions: The high variation found at the seahorse MHIIb gene indicates that sex-role reversed species are capable of maintaining the high MHC diversity typical in most vertebrates. Whether such species have evolved the capacity to use MH-odor cues during mate choice is presently being investigated using mate choice experiments. If this possibility can be rejected, such systems would offer an exceptional opportunity to study the effects of natural selection in isolation, providing powerful comparative models for understanding the relative importance of selective factors in shaping patterns of genetic variation

Molecular cloning, differential expression and 3D structural analysis of the MHC class-II β chain from sea bass (Dicentrarchus labrax L.)

The major histocompatibility complex class I and II molecules (MHC-I and MHC-II) play a pivotal role in vertebrate immune response to antigenic peptides. In this paper we report the cloning and sequencing of the MHC class II b chain from sea bass (Dicentrarchus labrax L.). The six obtained cDNA sequences (designated as Dila-DAB) code for 250 amino acids, with a predicted 21 amino acid signal peptide and contain a 28 bp 50-UTR and a 478 bp 30-UTR. A multiple alignment of the predicted translation of the Dila-DAB sequences was assembled together with other fish and mammalian sequences and it showed the conservation of most amino acid residues characteristic of the MHC class II b chain structure. The highest basal Dila-DAB expression was found in gills, followed by gut and thymus, lower mRNA levels were found in spleen, peripheral blood leucocytes (PBL) and liver. Stimulation of head kidney leukocytes with LPS for 4 h showed very little difference in the Dila-DAB expression, but after 24 h the Dila-DAB level decreased to a large extent and the difference was statistically significant. Stimulation of head kidney leukocytes with different concentrations of rIL-1b (ranging from 0 to 100 ng/ml) resulted in a dose-dependent reduction of the Dila-DAB expression. Moreover, two 3D Dila-DAB*0101 homology models were obtained based on crystallographic mouse MHC-II structures complexed with D10 T-cell antigen receptor or human CD4; features and differences between the models were evaluated and discussed. Taken together these results are of interest as MHC-II structure and function, molecular polymorphism and differential gene expression are in correlation with disease resistance to virus and bacteria in teleost fish.L'articolo è disponibile sul sito dell'editore http://www.sciencedirect.com/This work was supported by the European Commission within the project IMAQUANIM (EC contract number FOOD-CT-2005-007103)

Beyond hybridization: the genetic impacts of non-reproductive ecological interactions of salmon aquaculture on wild populations

Cultured Atlantic salmon Salmo salar are of international socioeconomic value, and the process of domestication has resulted in significant behavioural, morphological, and allelic differences from wild populations. Substantial evidence indicates that direct genetic interactions or interbreeding between wild and escaped farmed Atlantic salmon occurs, genetically altering wild salmon and reducing population viability. However, genetic interactions may also occur through ecological mechanisms (e.g. disease, parasites, predation, competition), both in conjunction with and in the absence of interbreeding. Here we examine existing evidence for ecological and non-reproductive genetic interactions between domestic Atlantic salmon and wild populations and the potential use of genetic and genomic tools to resolve these impacts. Our review identified examples of genetic changes resulting from ecological processes, predominately through pathogen or parasite transmission. In addition, many examples were identified where aquaculture activities have either altered the selective landscape experienced by wild populations or resulted in reductions in population abundance, both of which are consistent with the widespread occurrence of indirect genetic changes. We further identify opportunities for genetic or genomic methods to quantify these impacts, though careful experimental design and pre-impact comparisons are often needed to accurately attribute genetic change to aquaculture activities. Our review indicates that ecological and non-reproductive genetic interactions are important, and further study is urgently needed to support an integrated understanding of aquaculture-ecosystem interactions, their implications for ecosystem stability, and the development of potential mitigation and management strategies

Assessing adaptive genetic variation for conservation and management of the European grayling (Thymallus thymallus)

In this PhD, functional genetic variation of European grayling (Thymallus thymallus) is assessed to inform conservation and management of the species. This study is the first to characterize immune variation at the Major Histocompatibility complex (MHC) in grayling. The MHC is a marker of high ecological relevance, because of the strong association between immunity and fitness. Taking advantage of advances in sequencing technology, an analytical pipeline optimized for high-throughput, efficient and accurate genotyping of multi-gene families in non-model species is presented. Immune genetic variation is compared to neutral marker data. Results confirm the hypothesis that neutral marker variation does not predict immune genetic variation. Further, the possible effect of supplementing wild populations with hatchery-reared fish on immune genetic variation is evaluated. Significantly lower estimates of heterozygosity were found in stocked than purely native populations. Lower differentiation at immune genes than at neutral markers are indicative of the effects of balancing selection acting upon the MHC, within purely native, but not stocked populations. Furthermore species distribution modelling is used to identify environmental parameters shaping the distribution of grayling. To evaluate risks imposed by climate change, the sensitivity of grayling to climatic variables and range changes under predicted future scenarios are assessed. Locally-optimised mitigation strategies are shown to increase habitat suitability estimates under conditions of climate change. Evolutionary dynamics between hosts and pathogens are important factors in determining an individual’s susceptibility to disease. Studying the microbiome is therefore a promising tool to investigate the risk of disease-mediated extinctions, in relation to environmental conditions and host genetics. This study presents a preliminary analysis on the microbiome of grayling to inform experimental design for future large-scale studies. Altogether, data presented here contribute to improve the management of European grayling. More broadly, it informs conservation research in general, demonstrating the value of taking multiple approaches

Landscape-scale variation in an anthropogenic factor shapes immune gene variation within a wild population

Understanding the spatial scale at which selection acts upon adaptive genetic variation in natural populations is fundamental to our understanding of evolutionary ecology, and has important ramifications for conservation. The environmental factors to which individuals of a population are exposed can vary at fine spatial scales, potentially generating localized patterns of adaptation. Here, we compared patterns of neutral and major histocompatibility complex (MHC) variation within an island population of Berthelot's pipit (Anthus berthelotii) to assess whether landscape-level differences in pathogen-mediated selection generate fine-scale spatial structuring in these immune genes. Specifically, we tested for spatial associations between the distribution of avian malaria, and the factors previously shown to influence that distribution, and MHC variation within resident individuals. Although we found no overall genetic structure across the population for either neutral or MHC loci, we did find localized associations between environmental factors and MHC variation. One MHC class I allele (ANBE48) was directly associated with malaria infection risk, while the presence of the ANBE48 and ANBE38 alleles within individuals correlated (positively and negatively, respectively) with distance to the nearest poultry farm, an anthropogenic factor previously shown to be an important determinant of disease distribution in the study population. Our findings highlight the importance of considering small spatial scales when studying the patterns and processes involved in evolution at adaptive loci