Validation of a vigour index for trawl-caught Norway lobsters (Nephrops norvegicus) destined for the live market: underlying links to both physiological condition and survivability

Recent improved practices in the trawl fishery of Norway lobsters (Nephrops norvegicus) have made it possible to increase the proportion of these trawl-caught lobsters that can be transported alive successfully. A major contributor to this has been the introduction of on-board seawater tanks, which allow for the recovery of animals immediately after they have been landed from the net. In this study, we have validated a vigour index that could be used both by by fisheries scientists and the industry dealing with live-traded Nephrops to screen out the proportion of trawl-caught lobsters that nevertheless fail to recover following capture and are not in a condition to survive live transportation. Results indicate that the process of visual selection into one of four possible vigour categories reflects with good accuracy the underlying physiological state of the animals, as assessed by the level of adenylate 5’ -triphosphate (ATP) in the tail muscles, by the proportions of other nucleotides as expressed in the Adenylate Energy Charge (AEC), and by the amount of intra-muscular L-lactate present. The vigour index also correlates well with their subsequent survival potential in a semi-dry transport system

Bacterial iron acquisition mediated by outer membrane translocation and cleavage of a host protein

Iron is an essential micronutrient for most bacteria and is obtained from iron-chelating siderophores or directly from iron-containing host proteins. For Gram-negative bacteria, classical iron transport systems consist of an outer membrane receptor, a periplasmic binding protein, and an inner membrane ABC transporter, which work in concert to deliver iron from the cell surface to the cytoplasm. We recently showed that Pectobacterium spp. are able to acquire iron from ferredoxin, a small and stable 2Fe-2S iron sulfur cluster containing protein and identified the ferredoxin receptor, FusA, a TonBdependent receptor that binds ferredoxin on the cell surface. The genetic context of fusA suggests an atypical iron acquisition system, lacking a periplasmic binding protein, although the mechanism through which iron is extracted from the captured ferredoxin has remained unknown. Here we show that FusC, an M16 family protease, displays a highly targeted proteolytic activity against plant ferredoxin, and that growth enhancement of Pectobacterium due to iron acquisition from ferredoxin is FusC-dependent. The periplasmic location of FusC indicates a mechanism in which ferredoxin is imported into the periplasm via FusA before cleavage by FusC, as confirmed by the uptake and accumulation of ferredoxin in the periplasm in a strain lacking fusC. The existence of homologous uptake systems in a range of pathogenic bacteria suggests that protein uptake for nutrient acquisition may be widespread in bacteria and shows that, similar to their endosymbiotic descendants mitochondria and chloroplasts, bacteria produce dedicated protein import systems

Towards the humane slaughter of decapod crustaceans: identifying the most effective indicators of insensibility following electrical stunning

Decapod crustaceans provide a valuable food source worldwide, both through wild capture and captive rearing. They are also used extensively in scientific research, both as subjects for the investigation of basic biological processes and as model organisms for the detection of environmental changes. There is now an increasing acceptance that decapod crustaceans are sentient, and legislation is being introduced in numerous countries to ensure crustacean welfare when they are harvested or held captive. Moreover, methods for the humane slaughter of these animals are being developed, and of these electrical stunning is a prime candidate. Optimisation of electrical stunning is underway for a range of commercially-exploited or scientifically-important species, and the present study contributes to that process by examining further crab (Carcinus maenas) and lobster (Homarus gammarus) species using a rigorous neurophysiological approach. By recording nerve activity in both the central and peripheral nervous systems, we have found that electrical stunning with a standard commercial instrument arrests nerve activity in both these species at all levels: sensory, motor and central, rendering the animals neurologically insensible. This methodology is the most direct and effective way to establish if insensibility is successfully achieved. However, ultimately the routine monitoring of effective stunning in commercial and laboratory settings will have to depend on simple, yet reliable physiological or behavioural indicators, following their calibration against neurological methods. Monitoring heartbeat is used widely to establish metabolic activity, locomotory performance, agonistic interactions and responses to environmental conditions. We have therefore assessed the potential to use cardiac activity as an indicator for the state of sensibility. We recorded the heartbeat in both C. maenas and H. gammarus before and after electrical stunning, but find that in many cases even though nerve activity has ceased both centrally and peripherally, cardiac activity actually continues (though at a reduced rate) for a substantial time (>1h). The heartbeat is therefore not a reliable indicator of the state of sensibility, making it an unsuitable indicator of effective stunning. Possible reasons for these findings, and ways to validate behavioural measures that may be more appropriate for routinely establishing effective electrical stunning, are discussed

Dietary effects on insulin and glucagon

34 p., 5 tables, 2 figures and bibliographyThe effects of dietary amino acid profile (based on muscle (M) or whole body composition (WB) and the balance between indispensable (IAA) and dispensable amino acids (DAA) in the diet, on plasma levels of insulin and glucagon, were analysed in rainbow trout and gilthead sea bream. Plasma insulin values (baseline and 6 h postfeeding) were higher in trout than in sea bream, but the relative postfeeding increase was more pronounced in sea bream. Within the same dietary amino acid profile, diets with lower IAA/DAA, had a lower effect on the postfeeding secretion of insulin in both species. Circulating levels of glucagon (baseline and postfeeding relative increases) were higher in sea bream. In trout, diets with WB amino acid profile had a greater secretory effect on postfeeding glucagon than did diets with M profile, while gilthead sea bream showed an inverse response to circulating glucagon with respect to diet. Muscle insulin and insulin growth factor-I binding parameters were not affected by the dietary regimen. The postfeeding glucagon response depends on both the dietary AA profile and the fish species, while that of insulin seems to be more uniform, and is affected in a similar way regardless of the species.This study was funded by the European Union (Q5RS-2000–30068) “Perspectives of Plant Protein Use in Aquaculture” and by the Centre de Referencia de Recerca Desenvolupament en Aqüicultura de la Generalitat de Catalunya (CRA-2003–2.2/ 333038)

Effectiveness and quality evaluation of electrical stunning versus chilling in Norway lobsters (Nephrops norvegicus)

In the last decade, public interest in the welfare of decapod crustaceans has increased in many parts of the world. This has led to changes in legislation on methods for slaughter in a number of countries, while in others pressure for regulation changes is growing. Electro-stunning may have the potential for reducing noxious stimuli experienced by crustaceans during slaughter. However, data on activity in the central nervous system (CNS) and product quality-related data (indicative of consumer acceptability) are not available for most of the important decapod crustaceans, including the commercially valuable Norway lobster, Nephrops norvegicus. In this study, recordings of nerve activity showed that electro-stunning can render N. norvegicus rapidly insensible qualifying it as a potential humane slaughter procedure. In contrast, placing lobsters on ice for 30 min did not suppress neural activity. In terms of subsequent shelf life, results at day 7 based on QIM, total bacteria counts, H2S-producing bacteria, muscle pH, TMA and biogenic amines indicate no significant differences between the methods of stunning. From a quality perspective, electro-stunning did shorten the period that the product would be considered fresh (higher K-values up to day 5) and triggered faster melanosis development in the cephalothorax, an effect possibly linked to the increased temperature recorded in this area due to the imposed electrical current. However, no significant differences were detected on the cooked products by a trained sensory taste panel. While shelf life is not affected by the electro-stunning process, care should nevertheless be taken to avoid melanosis development, and the consumer perception of freshness in electro-stunned product should be studied further

Seasonal nutritional status in Norway lobsters, Nephrops norvegicus (L.): Are females nutritionally compromised over the winter? (Forthcoming)

Norway lobsters, Nephrops norvegicus, are sediment-dwelling decapod crustaceans that excavate burrows from which they make short excursions to feed by predation and scavenging. The females of this species are known to reside within their burrows for an extended period of time over the winter while brooding their eggs. The aim of this study was to assess the likelihood of these females being able to feed during this brooding period. Biophysical and biochemical measurements that had previously been shown to change with starvation under laboratory conditions in male N. norvegicus were taken for female N. norvegicus under similar conditions. These measurements were also compared in both sexes obtained from monthly trawl samples from the Clyde Sea Area, Scotland, UK, together with trawl composition data. The laboratory study showed that the hepatosomatic index, and the copper, lipid and water content of the hepatopancreas can be used as indicators of the state of starvation in females, as in males. In the wild, both sexes have reduced nutritional status during the winter, but not to the degree seen in animals starved for 20 weeks in aquarium trials. This study does not support the hypothesis that females cease feeding over winter, during their brooding period. Firstly, some females were unable to sustain ovary development during starvation under controlled conditions, contrary to field observations. Secondly, field data suggests that there is no sex-specific reduction in nutritional status

Mycotoxins in aquaculture: feed and food

Mycotoxins, secondary metabolites produced by moulds, are responsible for causing significant economic losses due to spoilage of agricultural products but also due to direct or indirect health impact on livestock upon ingestion of mycotoxin contaminated feedstuffs. Aquaculture farmed species are not an exception and studies reporting mycotoxin‐related issues in the aquaculture industry have been increasing. However, our understanding on the prevalence and impact of mycotoxins in the aquaculture sector is still lower compared to the terrestrial livestock sector. Consequently, regulatory limits and guidance values have been defined based on the studies on terrestrial farm animals. The aim of this review is to compile and critically assess mycotoxin occurrence and co‐occurrence in aquaculture finished feeds, and understand the risk of mycotoxin carry‐over in aquaculture seafood products. Furthermore, we aim with this review to raise awareness to the scientific community, the regulatory authorities and the aquaculture industry to the need for specific aquaculture mycotoxin maximum concentration levels for both aquaculture feeds and foods

Plasma proteome profiling of freshwater and seawater life stages of rainbow trout (Oncorhynchus mykiss)

The sea-run phenotype of rainbow trout (Oncorhynchus mykiss), like other anadromous salmonids, present a juvenile stage fully adapted to life in freshwater known as parr. Development in freshwater is followed by the smolt stage, where preadaptations needed for seawater life are developed making fish ready to migrate to the ocean, after which event they become post-smolts. While these three life stages have been studied using a variety of approaches, proteomics has never been used for such purpose. The present study characterised the blood plasma proteome of parr, smolt and post-smolt rainbow trout using a gel electrophoresis liquid chromatography tandem mass spectrometry approach alone or in combination with low-abundant protein enrichment technology (combinatorial peptide ligand library). In total, 1,822 proteins were quantified, 17.95% of them being detected only in plasma post enrichment. Across all life stages, the most abundant proteins were ankyrin-2, DNA primase large subunit, actin, serum albumin, apolipoproteins, hemoglobin subunits, hemopexin-like proteins and complement C3. When comparing the different life stages, 17 proteins involved in mechanisms to cope with hyperosmotic stress and retinal changes, as well as the downregulation of nonessential processes in smolts, were significantly different between parr and smolt samples. On the other hand, 11 proteins related to increased growth in post-smolts, and also related to coping with hyperosmotic stress and to retinal changes, were significantly different between smolt and post-smolt samples. Overall, this study presents a series of proteins with the potential to complement current seawater-readiness assessment tests in rainbow trout, which can be measured non-lethally in an easily accessible biofluid. Furthermore, this study represents a first in-depth characterisation of the rainbow trout blood plasma proteome, having considered three life stages of the fish and used both fractionation alone or in combination with enrichment methods to increase protein detection

Tomato Juice Consumption Modifies the Urinary Peptide Profile in Sprague-Dawley Rats with Induced Hepatic Steatosis

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disorder in Western countries, with a high prevalence, and has been shown to increase the risk of type 2 diabetes, cardiovascular disease (CVD), etc. Tomato products contain several natural antioxidants, including lycopene—which has displayed a preventive effect on the development of steatosis and CVD. Accordingly, the aim of the present work was to evaluate the effect of tomato juice consumption on the urinary peptide profile in rats with NAFLD induced by an atherogenic diet and to identify potential peptide biomarkers for diagnosis. Urine samples, collected weekly for four weeks, were analyzed by capillary electrophoresis (CE) coupled to a mass spectrometer (MS). A partial least squares-discriminant analysis (PLS-DA) was carried out to explore the association between differential peptides and treatments. Among the 888 peptides initially identified, a total of 55 were obtained as potential biomarkers. Rats with steatosis after tomato juice intake showed a profile intermediate between that of healthy rats and that of rats with induced hepatic steatosis. Accordingly, tomato products could be considered as a dietary strategy for the impairment of NAFLD, although further research should be carried out to develop a specific biomarkers panel for NAFLD