Summer Mortality of Hatchery-produced Pacific Oyster Spat (Crassostrea gigas). I. Estimation of Genetic Parameters for Survival and Growth

The multidisciplinary project "MOOREST" aims to improve our understanding of causes of summer mortality in "Crassostrea gigas" juveniles in France and to reduce its its impact on oyster production. As part of the MOREST project, 43 full-sib families nested within 17 half-sib families were produced, planted out and tested in 3 sites during summer 2001 to assess to what extent genetic variability exists for this trait. A strong genetic basis was found for survival as narrow-sense heritability estimates ranged from 0.47 to 1.08, with higher values in sites where summer mortality was higher. Genetic correlations across sites were positive and very high for survival, indicating no genotype by environment interaction. In contrast, lower genetic variation was observed for growth in all sites. Finally, genetic correlations between growth and survival were low, in all sites. Selective breeding in a single site should therefore be an efficient means of improving survival in oysters less than one year old along the French Atlantic and Channel coastlines with only very limited effects on growth. As yield mostly depends on survival and growth, this approach should significantly improve harvestable yield. Possible reasons why a high genetic variance for survival appears to be maintained in wild populations are discussed

Phenotypic and Genetic Consequences of Size Selection at the Larval Stage in the Pacific Oyster (Crassostrea gigas)

The life histories of oysters in the genus "Crassostrea", like those of most marine bivalves, are typified by high fecundity and low survival in nature. Rearing conditions in hatcheries however ensure optimized density, diet, and temperature. Hatcheries are becoming increasingly important for the production of juveniles in aquaculture, and their culture practices often include culling of slow growing larvae to reduce and synchronize the time taken to reach settlement. Because previous studies have found substantial genetic variation for early life developmental traits in "Crassostrea gigas", these culling practices are likely to cause highly different selective pressures in hatcheries from those in the natural environment. We studied the phenotypic and genetic impact of such culling practices in a factorial cross between 10 males and 3 females subjected to progressive culling of the smallest 50% of larvae, compared with a non-culled control. Measurements were made on larval growth, survival, time taken to attain pediveliger stage and settlement success. Culling had a larger effect on the variance of these larval traits than on their means. The larvae in culled cultures were approximately 10% larger than those in controls, whereas the coefficient of variation was reduced by 30 -40%. Culling also reduced the mean time to settlement by 12% and its variance by 55%. Using a multiplexed set of microsatellite markers to trace parentage, we also estimated the variance in reproductive success in a controlled experiment to quantify the consequences of intensive hatchery rearing practices. We also focused on changes in effective population size and genetic structure over time (and developmental stages). Our results show a loss of genetic diversity following removal of the smallest larvae by culling, as well as temporally varying genetic structure of the larval population. This supports the existence of genetic variability in early life developmental traits in C. gigas. Culling in hatcheries, like size-related selective pressures in the wild, are likely to have a significant genetic impact, through their effects on the timing of settlement

Invasion genetics of the Pacific oyster Crassostrea gigas in the British Isles inferred from microsatellite and mitochondrial markers

The Pacific oyster, Crassostrea gigas, native to northeast Asia, is one of the most important cultured shellfish species. In Europe, Pacific oysters first settled along the Atlantic coasts of France at the end of the 1960s but rapidly spread and are now widely established. Twenty-two sites in the United Kingdom (UK), Ireland, Denmark, France and Spain were sampled to assess genetic diversity and differentiation. Hatchery-propagated stocks from two hatcheries located in the UK also were included. Two main genetic clusters were identified from pairwise genetic differentiation indexes, Bayesian clustering methods or neighbour-joining analysis, based on 7 microsatellite loci: (1) a Northeast cluster (including feral samples from East England, Ireland and Denmark as well as UK hatchery stocks) and (2) a Southwest cluster (including samples from South Wales, South West England, France and Spain). The Southwest cluster had significantly higher allelic richness (A) and expected heterozygosity (He) (A: 45.68, He: 0.928) than in the Northeast (A: 26.58, He: 0.883); the two diverging by a small but significant FST value (FST=0.017, 95% CI: 0.014-0.021). A 739-bp fragment of the major noncoding region of the mitochondrial genome was sequenced in 248 oysters from 12 of the studied samples in Europe and in 25 oysters from Miyagi prefecture (Japan). A total of 81 haplotypes were found. Haplotype frequency analyses identified the same two clusters observed using microsatellites. This study highlights how the number and size of introduction events, aquaculture practices, genetic bottlenecks followed by genetic drift and natural dispersal can act concurrently to shape the genetic diversity and structure of introduced populations

Neonatal high protein intake enhances neonatal growth without significant adverse renal effects in spontaneous IUGR piglets.

In humans, early high protein (HP) intake has been recommended to prevent postnatal growth restriction and complications of intrauterine growth restriction (IUGR). However, the impact of such a strategy on the kidneys remains unknown, while significant renal hypertrophy, proteinuria, and glomerular sclerosis have been demonstrated in few experimental studies. The objective of this study was to evaluate the effects of a neonatal HP formula on renal structure in IUGR piglets. Spontaneous IUGR piglets were randomly allocated to normal protein (NP, javax.xml.bind.JAXBElement@68d5845e  = 10) formula or to HP formula (+50% protein content, javax.xml.bind.JAXBElement@3e768c15  = 10) up to day 28 after birth. Body weight, body composition, renal functions, and structure were assessed at the end of the neonatal period. While birth weights were similar, 28-day-old HP piglets were 18% heavier than NP piglets ( javax.xml.bind.JAXBElement@206b72ec < javax.xml.bind.JAXBElement@7f241a6d 0.01). Carcass protein content was 22% higher in HP than in NP offspring ( javax.xml.bind.JAXBElement@3b9786a3 < javax.xml.bind.JAXBElement@318ba3e0 0.01). Despite a HP intake, kidney weight and glomerular fibrosis were unaltered in HP piglets. Only a 20% increase in glomerular volume was noted in HP piglets ( javax.xml.bind.JAXBElement@4a0c5b2f  < 0.05) and restricted to the inner cortical area nephrons ( javax.xml.bind.JAXBElement@1524c771 = javax.xml.bind.JAXBElement@1281f9e8 0.03). Plasma urea/creatinine ratio and proteinuria were unchanged in HP piglets. In conclusion, neonatal HP feeding in IUGR piglets significantly enhanced neonatal growth and tissue protein deposition but mildly affected glomerular volume. It can be speculated that a sustained tissue protein anabolism in response to HP intake have limited single nephron glomerular hyperfiltration

Playing With Time: Gay Intergenerational Performance Work and the Productive Possibilities of Queer Temporalities

This article examines the tendencies of LGBT intergenerational theater projects. By engaging with ideas of queer time, temporal drag, and the pervasive heteronormative imagery of heritability and inheritance, this article explores the possibility that LGBT intergenerational projects may generate some of the problems they aim to challenge. Through the lens of queer time, the article describes the normativity generated in LGBT intergenerational theater projects as a form of restrictive interpellation. The article explores the temporal complexities at play in such theater productions as The Front Room, a specific LGBT intergenerational theater project performed in the United Kingdom in 2011. The article concludes by noting some ways in which intergenerational theater projects might seek to work through the embodiment of the historical quotidian as a mode of resistance to normativity’s recirculation

Detailed insights into pan-European population structure and inbreeding in wild and hatchery Pacific oysters (Crassostrea gigas) revealed by genome-wide SNP data.

Cultivated bivalves are important not only because of their economic value, but also due to their impacts on natural ecosystems. The Pacific oyster (Crassostrea gigas) is the world's most heavily cultivated shellfish species and has been introduced to all continents except Antarctica for aquaculture. We therefore used a medium-density single nucleotide polymorphism (SNP) array to investigate the genetic structure of this species in Europe, where it was introduced during the 1960s and has since become a prolific invader of coastal ecosystems across the continent. We analyzed 21,499 polymorphic SNPs in 232 individuals from 23 localities spanning a latitudinal cline from Portugal to Norway and including the source populations of Japan and Canada. We confirmed the results of previous studies by finding clear support for a southern and a northern group, with the former being indistinguishable from the source populations indicating the absence of a pronounced founder effect. We furthermore conducted a large-scale comparison of oysters sampled from the wild and from hatcheries to reveal substantial genetic differences including significantly higher levels of inbreeding in some but not all of the sampled hatchery cohorts. These findings were confirmed by a smaller but representative SNP dataset generated using restriction site-associated DNA sequencing. We therefore conclude that genomic approaches can generate increasingly detailed insights into the genetics of wild and hatchery produced Pacific oysters

New insights on the population genetic structure of the great scallop (Pecten maximus) in the English Channel coupling microsatellite data and demogenetic simulations.

International audienceThe great scallop (Pecten maximus) is a commercially important bivalve in Europe, particularly in the English Channel, where fisheries are managed at regional and local scales through the regulation of fishing effort. In the long term, knowledge about larval dispersal and gene flow between populations is essential to ensure proper stock management. Yet, previous population genetic studies have reported contradictory results. In this study, scallop samples collected across the main fishing grounds along the French and English coasts of the English Channel (20 samples with temporal replicates for three sites,n= 1059 individuals), and the population genetic structure was analysed using 13 microsatellite loci. Coupling empirical genetic data with demogenetic modelling based on a biophysical model simulating larval exchanges among scallop beds revealed a subtle genetic differentiation between south-west English populations and the rest of the English Channel, which was consistent with larval dispersal simulations. The present study provides a step forward in the understanding of great scallop population biology in the English Channel, underlining the fact that even in a context of potentially high gene flow and recent divergence times since the end of the last glacial maximum, weak but significant spatial genetic structure can be identified at a regional scale

Construction and commissioning of a technological prototype of a high-granularity semi-digital hadronic calorimeter

A large prototype of 1.3m3 was designed and built as a demonstrator of the semi-digital hadronic calorimeter (SDHCAL) concept proposed for the future ILC experiments. The prototype is a sampling hadronic calorimeter of 48 units. Each unit is built of an active layer made of 1m2 Glass Resistive Plate Chamber(GRPC) detector placed inside a cassette whose walls are made of stainless steel. The cassette contains also the electronics used to read out the GRPC detector. The lateral granularity of the active layer is provided by the electronics pick-up pads of 1cm2 each. The cassettes are inserted into a self-supporting mechanical structure built also of stainless steel plates which, with the cassettes walls, play the role of the absorber. The prototype was designed to be very compact and important efforts were made to minimize the number of services cables to optimize the efficiency of the Particle Flow Algorithm techniques to be used in the future ILC experiments. The different components of the SDHCAL prototype were studied individually and strict criteria were applied for the final selection of these components. Basic calibration procedures were performed after the prototype assembling. The prototype is the first of a series of new-generation detectors equipped with a power-pulsing mode intended to reduce the power consumption of this highly granular detector. A dedicated acquisition system was developed to deal with the output of more than 440000 electronics channels in both trigger and triggerless modes. After its completion in 2011, the prototype was commissioned using cosmic rays and particles beams at CERN.Comment: 49 pages, 41 figure

A Scientific Name for Pacific Oysters

WOS:000447083800041International audienc