Maternal effects on oocyte quality in farmed Atlantic halibut (Hippoglossus hippoglossus L.)

Atlantic halibut (Hippoglossus hippoglossus) oocyte quality is highly variable and one of the major bottlenecks during fry-production for on-growth in commercial Atlantic halibut farming. In this study, the effect of maternally derived oocyte constituents (i.e. yolk components and mRNAs) on oocyte quality (i.e fertilisation, embryonic hatching and normal blastomere symmetry) in farmed Atlantic halibut has been investigated. Atlantic halibut embryos and larvae depend on nutritional yolk components until larval first feeding. The importance of yolk n-3 fatty acids for oocyte quality was confirmed. However, highest positive correlations with oocyte quality were found for the less studied fatty acids dihomo-γ-linolenic acid (DGLA, 20:3n6) and docosapentaenoic acid (DHA, 20:5n3) that are known to compete with two of the most abundant fatty acids, arachidonic acid (ARA, 20:4n6)and docosahexaenoic acid (DPA, 22:5n3), respectively during fatty acid metabolism. High methionine and aspartic concentrations, amino acids essential to eukaryotic protein synthesis, were found to influence oocyte quality positively while no significant correlations were found between oocyte folate concentrations and oocyte quality. Before activation of zygotic transcription, maternal mRNAs control cell divisions and embryonic patterning. Due to the limited available genomic information on Atlantic halibut maternal transcripts, an expressed sequence tag (EST) maternal library containing 2,341high quality ESTs was created by suppressive subtractive hybridization (SSH). The maternal library constitutes an EST pool to identify suitable Atlantic halibut reference genes and identify differentially expressed maternal genes in high and low quality Atlantic halibut oocytes. To perform reliable quantification of gene expression by qPCR, stable reference genes have to be used to normalize target gene expression. Tubb2/Actb and Tbb2/Fau were identified as the best two-gene normalization factors during Atlantic halibut embryonic and larval development. Either of these normalization factors can be used for future developmental gene expression studies in Atlantic halibut. Tubb2/Actb was further used as reference gene during this study. Poor embryonic hatching success was found to not be correlated with a general decrease in oocyte maternal transcript abundance but with low transcript levels of specific maternal transcripts by qPCR. The majority of genes showed either no or very minor correlations between their transcript levels and oocyte quality parameters (Fertilisation: 13-93 %, embryonic hatching: 1-94 %). However, maternal transcript levels of three genes, most likely involved in nuclear protein and mRNA transport, growth factor regulation, and embryonic patterning, correlated with oocyte quality. Further, a new Atlantic halibut 4x44k oligonucleotide microarray was constructed and used to identify 192 strictly maternal genes during Atlantic halibut embryonic development and 20 differentially expressed genes between high and low quality oocytes, involved in immune response, metabolism, RNA transcription, protein degradation, cell signalling and the cytoskeleton. Microarray validation confirmed its suitability for future gene expression studies during Atlantic halibut embryonic development. The identified maternal genes in this study can serve as a pool for future in-depth studies of embryonic gene expression to advance the knowledge of important developmental processes such as germ cell development, growth and immune response in Atlantic halibut. Some of these may serve as possible markers for Atlantic halibut oocyte quality due to their high expression differences between high and low quality oocytes. Future nutritional studies on Atlantic halibut broodstock should focus on the identified yolk constituents acting positively on oocyte quality

Freight demand generation on commodity and loading unit level

Freight sustains our daily lives and economy. Information on its characteristics, its production and consumption locations and its modes of transport are consequently of a crucial importance for private and public decision makers. This paper presents a freight generation model for the Belgian territory. Based on data gathered on transport flows by commodity type and loading unit and data on population density and business establishments with their characteristics, generated and attracted freight volumes were obtained for 4934 zones subdividing the country. A generalized linear regression analysis with log link was used to do so. Both generated and attracted volumes are connected to one another by a conditional probability function, resulting in an origin-destination matrix. The analysis is to our knowledge unique as modelled volumes and flows can be distinguished by commodity types and loading unit, and this at very detailed geographical scale. This will lead to new in-depth analyses and added value, including effects of loading unit dependent logistics cost structures

A Sustainability Assessment Framework for On-Site and Off-Site Construction Logistics

Urban areas pay increasing attention to new construction and infrastructure works, mainly due to the rapid global rise in urbanisation. In the long run, these works have a positive correlation with the economic and social attractiveness of cities. Construction strongly relies on logistics activities, which cannot be neglected in the environmental equation. An important aspect in tackling the negative effects of construction logistics (CL) lies in understanding the source and mitigation potential of the impacts incurred. However, currently, limited robust impact assessments are available for this sector. Given the lack of these rigorous assessments, it is difficult to evaluate the environmental criteria concerned, especially when comparing innovative CL solutions. In this paper, we present a holistic sustainability assessment framework designed for CL activities based on life cycle approaches, which covers four main iterative steps: (1) goal and scope definition, (2) data identification and availability, (3) scenario and setup evaluation and (4) environmental impact assessment. To measure both the off-site and on-site CL impact, two distinct and complementary methodologies are used: External Cost Calculations and Life Cycle Assessment. The framework was implemented on a pilot case in the Brussels-Capital Region (Belgium). It provides a holistic view of CL impacts for policy evaluations and implementations on the project, portfolio or city level. The results show that off-site zero-emission construction vehicles are the way forward if cities want to achieve environmental goals by 2035. However, market readiness for high-capacity vehicles must be considered. Otherwise, the positive effects on air pollution, climate change and noise are offset by a saturation of the road transport network and its associated congestion and infrastructure damage costspublishedVersio

Production of sterile Atlantic salmon by germ cell ablation with antisense oligonucleotides

Cultivation of sterile-only fish in aquaculture offers multiple benefits of environmental, economical, and social value. A reliable method for efficient sterilization without affecting fish welfare and performance traits would have significant impact on fish production practices. Here, we demonstrate sterilization of Atlantic salmon embryos by targeting the dead end gene with antisense oligonucleotides. Successful gene knock down and sterilization was achieved only when using Gapmer oligonucleotides and not with morpholino oligos. Germ cell-depleted embryos developed into morphologically normal male and female salmon with rudimentary gonads devoid of gametes

Earlier or delayed seasonal broodstock spawning changes nutritional status and metabolic programming of growth for next-generation Atlantic salmon

Atlantic salmon (Salmo salar) breeding companies depend on changing light, temperature and feeding regimes to achieve new generations outside the natural spawning season. However, there have been few conducted trials reported that have studied whether this shift affects important traits. We test whether an induced shift of two months earlier or two months later than normal spawning season affects the nutritional status (folate, methionine, vitamin B12, vitamin B6, free amino acids, N-metabolites and lipids) in broodstock liver and muscle and whether this affects the levels of the same nutrients in the offspring. The results showed significant seasonal differences in the Cahill cycle (glucose-alanine cycle), 1C metabolism and for free amino acids catabolized in the citric acid cycle all which are important for embryonic growth The broodstock nutritional status was reflected in the eggs. Nutritional status of broodstock liver and muscle and newly fertilized eggs showed two general scenarios: Advanced spawning period did not obtain optimal deposition of nutrients in the eggs. Delayed spawning broodstock displayed a metabolic profile which indicated that it had enhanced catabolization of muscle protein which led to accumulation of aminogroups from muscle breakdown to such a degree that these amino groups were increased in the eggs. The total body weight at start-feeding stage revealed best growth for both the normal and late spawning compared to early spawning. We show here that environmental alterations in broodstock husbandry influence the nutrient status of the next generation via nutritional and metabolic programming. This is an important concept which needs more careful awareness as the metabolism compensate and regulate the energy between catabolism and anabolism through the early stages of cell divisions which give rise to changes in permanent traits for the next generation.publishedVersio

Ultrasonic imaging as a means of monitoring gonadal development in lumpfish (Cyclopterus lumpus)

The commercial farming of juvenile lumpfish requires monitoring of gonadal development to achieve synchronized production. Conventional methods such as gonadosomatic index (GSI), sex hormone analyses, gonadal histology, endoscopy, and gene expression analyses are costly, invasive, and often involve sacrificing the fish. We assessed the efficiency of ultrasound as a non-invasive method for monitoring gonadal development in lumpfish. Based on ultrasound observations, we categorized the fish into six stages; F0 to F5 for females and M0 to M5 for males, that represented maturity levels from immature to spent. Importantly, the ultrasound gonadal stages aligned with histological gonadal stages. Additionally, ultrasound stages aligned with profiles of GSI, testosterone (T), 11-ketotestosterone, and 17β-estradiol throughout gonadal development including the spawning period. Moreover, these parameters exhibited significant positive correlations with each other reflecting their parallel trends during gonadal development. To minimize the frequency of ultrasound usage and fish handling, we established F3 and M3/M4 as arbitrary thresholds for identifying ripe females and males, respectively. By using these thresholds, the need for regular ultrasound monitoring could be reduced during most of the rearing period. Ultrasound proves to be useful and reliable for monitoring gonadal development in lumpfish, enabling synchronized production of juvenile fish

Maternal gene expression in Atlantic halibut (Hippoglossus hippoglossus L.) and its relation to egg quality

<p>Abstract</p> <p>Background</p> <p>The commercial production of Atlantic halibut (<it>Hippoglossus hippoglossus </it>L.) suffers from a major bottleneck due to the low success of producing juveniles for on-growing. Atlantic halibut females are routinely hand-stripped and incorrect timing of stripping can result in low quality eggs due to post-ovulatory aging. Post-ovulatory aging leads to compositional changes in eggs that include maternally provided proteins and RNAs. There have been few studies of the maternally provided mRNA transcripts that control early development in commercially important fish species. The present study aimed to study maternal gene expression in Atlantic halibut and its relation to egg quality parameters including blastomere symmetry and hatching success.</p> <p>Results</p> <p>A maternal EST library containing 2341 sequences was constructed by suppressive subtractive hybridisation. Thirty genes were selected for expression studies; 23 novel genes and 7 genes with documented roles in early development. The expressions of twenty-one selected genes were measured by qPCR from fertilization to the 10-somite stage. Three genes were identified as strictly maternal genes that were expressed until the start of gastrulation; <it>askopos </it>(<it>kop</it>), <it>si:dkey-30j22.9 </it>(Tudor family member), and <it>Tudor 5 protein </it>(<it>Tdrd5</it>). The expressions of 18 genes at the 8-cell stage were correlated with egg quality parameters. The majority of genes showed either no or very minor correlations with egg quality parameter. However, two genes correlated positively with hatching success (<it>r</it>> 0.50, HHC00353: <it>r </it>= 0.58, <it>p </it>< 0.01; HHC01517: <it>r </it>= 0.56, <it>p </it>< 0.01) and one gene (HHC00255) was negatively correlated with the percentage of normal blastomeres (<it>r </it>= -0.62, <it>p </it>< 0.05).</p> <p>Conclusions</p> <p>During this study we have related maternal levels of gene expression to hatching success in fish. Poor hatching success was not correlated with a general decrease in transcript abundance but with low transcript levels of some specific genes. Thus, the molecular mechanisms leading to low Atlantic halibut egg quality cannot be entirely explained by post-ovulatory aging.</p

Out-of-season spawning affects the nutritional status and gene expression in both Atlantic salmon female broodstock and their offspring

The Atlantic salmon aquaculture industry relies on adjustments of female broodstock spawning season to meet the demand for delivery of embryos outside the natural spawning season. Earlier results from zebrafish have shown that parental micronutrient status program offspring metabolism. Therefore, the main hypothesis of this study was to investigate if out-of-season (off-season) broodstock (spawning in June, in land-based recirculation systems) and their offspring deviate in micronutrient status when compared to broodstock and offspring from normal spawning season. Both seasons of female Atlantic salmon broodstock were fed the same diet and starved for approximately the same time interval prior to spawning. We compared nutrients related to the 1C metabolism (vitamin B12, folate, vitamin B6, methionine), free amino acids (FAAs) and lipid classes in broodstock muscle and liver tissues, and during offspring ontogeny. In general, the off-season broodstock showed higher levels of folate, vitamin B6 and selected FAAs in muscle tissue, and higher levels of folate and lipids (cholesterol and sphingomyelin) in liver tissue compared to normal-season. Furthermore, embryos from off-season had reduced amounts of all the measured lipid classes, like cholesterol and sphingomyelin, and lower levels of one type of folate and changes in FAAs and N-metabolites. We discovered significant differences between the seasons in mRNA levels of genes controlling fatty acid synthesis and 1C metabolism in both broodstock liver and offspring. Moreover, for genes controlling the methylation of DNA; both maintenance and de novo DNA methyltransferases (DNMTs) were expressed at higher levels in off-season compared to normal-season offspring. Our results show, in general that normal spawning season broodstock allocated more nutrients to eggs than off-season. Our results indicate a potential for improved maturation for off-season group to obtain a higher offspring growth potential, and this argues for a reassessment of the nutritional influence from broodstock to offspring and the consequences through nutritional programming.publishedVersio

Spawning manipulation, broodfish diet feeding and egg production in farmed Atlantic salmon

Atlantic salmon aquaculture relies on continuous supply of high quality eggs. Broodfish nutrition and manipulation of ovulation time (photoperiod and temperature) are key factors. The optimum feeding period with broodfish diet has not been investigated before. The present study examined how feeding period with broodfish diet (9 vs. 17 months) interacted with manipulation of ovulation time (early (Nov), normal (Dec), late (Feb)) on broodstock egg production capacity and egg quality in two-sea-winter female Atlantic salmon (∼12 kg). All groups were fed until June 2021 when they were transferred to tanks and starved until ovulation.publishedVersio