Sparus Research Articles

Mercury in four common fishes sold in Algeria and associated humans risk.

This study aimed to analyse the concentrations of mercury in fish samples available in the Algerian market and evaluate the potential health risks associated with their consumption. A total of 135 fish samples, representing the species Sardina pilchardus, Merluccius merluccius, Sparus aurata and Auxis rochie, were collected and analysed. Mercury levels were determined using thermal decomposition amalgamation Atomic Absorption Spectrophotometry. Health risks were evaluated by calculating hazard quotients. The overall mean concentration was 0.19 ± 0.11 mg/kg across all species. Individual species concentrations were recorded as 0.17 ± 0.08 mg/kg for Sardina pilchardus, 0.26 ± 0.19 mg/kg for Merluccius merluccius, 0.27 ± 0.18 mg/kg for Sparus aurata and 0.23 ± 0.13 mg/kg for Auxis rochei. Hazard quotients were below 1, indicating low health risk for fish consumers. Nevertheless, it is recommended to conduct periodic monitoring of heavy metal levels in fish, coupled with ongoing risk assessments, to ensure continued consumer protection.

Dietary administration impact of olive pulp on growth performance, metabolic profile, immune status, and antioxidant potential of gilthead seabream (Sparus aurata L.)

Dietary administration impact of olive pulp on growth performance, metabolic profile, immune status, and antioxidant potential of gilthead seabream (Sparus aurata L.)

Identification and florfenicol-treatment of pseudomonas putida infection in gilthead seabream (Sparus aurata) fed on tilapia-trash-feed

The present study aimed to determine the major cause of the high mortality affecting farmed gilthead seabream (Sparus aurata) and controlling this disease condition. Fifteen diseased S. aurata were sampled from a private fish farm located at Eldeba Triangle, Damietta, fish showed external skin hemorrhages, and ulceration. Bacterial isolates retrieved from the diseased fish were identified biochemically as Pseudomonas putida and then confirmed by phylogenetic analysis of the 16 S rRNA gene sequence. P. putida was also isolated from three batches of tilapia-trash feed given to S. aurata. Biofilm and hemolytic assay indicated that all P. putida isolates produced biofilm, but 61.11% can haemolyse red blood cells. Based on the antibiotic susceptibility test results, P. putida was sensitive to florfenicol with minimum inhibitory concentrations ranging between 0.25 and 1.0 µg mL− 1, but all isolates were resistant to ampicillin and sulfamethoxazole-trimethoprim. Pathogenicity test revealed that P. putida isolate (recovered from the tilapia-trash feed) was virulent for S. aurata with LD50 equal to 4.67 × 107 colony forming unit (CFU) fish− 1. After intraperitoneal (IP) challenge, fish treated with 10 mg kg− 1 of florfenicol showed 16.7% mortality, while no mortality was recorded for the fish group that received 20 mg kg− 1. The non-treated fish group showed 46.7% mortality after bacterial challenge. HPLC analysis of serum florfenicol levels reached 1.07 and 2.52 µg mL− 1 at the 5th -day post-drug administration in the fish groups received 10 and 20 mg kg− 1, respectively. In conclusion, P. putida was responsible for the high mortality affecting cultured S. aurata, in-feed administration of florfenicol (20 mg kg− 1) effectively protected the challenged fish.

Genome-wide association analyses reveal genotype-by-environment interactions of growth and organ weights in gilthead seabream (Sparus aurata)

Gilthead seabream is one of the most important fish species for Mediterranean aquaculture. More than 80% of the genetically improved fingerlings of this species originate from a single country, Greece. A previous study revealed moderate genotype-by-environment (G x E) interactions for growth traits and organ weights between commercial production sites in Greece and Spain. The main objectives of this study were to identify QTLs and genes associated with growth traits and organ weights in gilthead seabream and to identify the biological processes and pathways controlling these traits under different temperature environments. For growth traits, we found fourteen genome-wide suggestive SNP effects in Spain. A strong peak between 1.97 Mb to 4.69 Mb on chromosome (chr) 22 was shared among three growth traits (harvest weight, fillet weight and thermal growth coefficient). Fourteen genome-wide suggestive SNP effects were also identified in Greece. However, none overlap with those found in Spain. Two SNPs on chr5 (chr5:5729959, chr5:2336903) and two SNPs on chr6 (chr6:1957732, chr6:3659811) were associated with all three growth traits. For organ weights, a total of 15 SNPs were associated above the suggestive threshold in Spain. Four SNPs (chr22:1966940, chr22:6094383, chr22:67838, chr15:16798259) are shared between viscera weight and liver weight, while one SNP (chr22:67838) is shared among viscera, liver and heart weight. Interestingly, three of these four SNPs (chr22:1966940, chr22:67838, and chr15:16798259) also overlap with significant SNPs associated with growth traits. None of the SNPs associated with viscera weight, liver weight and heart weight are shared with Greece. GO and KEGG functional enrichment analyses showed that light absorption and ECM-receptor interaction are significantly enriched with growth traits QTLs in Spain but not in Greece. For organ weights, response to stimulus is the most prominent process in Spain, while cell adhesion, and regulation of phosphorylation are more prominent in Greece. Genomic architectures for growth traits and organ weights differ between environments. These findings not only explain part of the G x E interactions, but also give insight into how genetics determines differences in how environmental conditions affect growth and organ weights.

Growth performance of gilthead sea bream (Sparus aurata) fed a mixture of single cell ingredients for organic diets

The aim of this study was to investigate the growth performance of gilthead sea bream (Sparus aurata) fed with a mixture of a single cell ingredient (SCI) (bacterial protein, yeast protein and algae) for organic aquaculture. Sea bream with an initial mean body weight of 6.87±0.07 g were randomly allocated to 250-litre tanks. Four isonitrogenous, isolipidic and isoenergetic diets were formulated by replacing organic fishmeal trimmings with 0% (control), 12% (SCI12), 15% (SCI15) and 18% (SCI18) of the SCI mixture. Each diet was distributed to the groups in triplicate. The fish were fed three times daily until satiation and the experimental period was 60 days. Survival rates and voluntary feed intake were similar in the fish with the different feed treatments (p > 0.05). Similar (p > 0.05) growth performance (final weight, SGR) and feed conversion ratio (FCR) were observed in fish fed all SCI-based diets, which was superior to the control diet treatment. Apparent protein digestibility was similar among treatments, but lipid digestibility was significantly reduced in the SCI15 and SCI18 groups compared to the SCI12 group. The specific activities of trypsin, total alkaline protease and lipase were increased in fish fed the SCI15 diet (p < 0.05). The protein content in the fillet was significantly increased and the lipid content was decreased in the SCI12 and SCI18 groups compared to the other groups. No adverse effects on liver and intestinal histology were observed in the different groups. The results suggest that organic fishmeal trimmings can be successfully replaced by innovative SCIs based on microbial protein, yeast meal and algae, and that this SCI mixture could be a candidate for organic aqua feed for gilthead sea bream.

Mitigation of ammonia concentrations for improving wet, live fish and crab transport conditions

The transport of live aquaculture species, both throughout the culture period and during marketing as live products, is far from optimized. In wet transports, the bottleneck is the total ammonia nitrogen (TAN) concentration that develops in the transport water. The effect of actively removing TAN from the water on the survival of fish and crabs during wet transport is herein reported. The TAN concentration was controlled by exchanging NH4+ with Na+ using self-synthesized polymer-coated zinc-hexa-cyanoferrate (Zn-HCF) cation-exchange material. Theoretical simulation followed by empirical experiments were carried out to mimic the transports of Gilthead seabream and European Brown crab, in the presence and absence of Zn-HCF. The Zn-HCF proved very efficient: while the TAN concentration in the seabream test tanks did not exceed the predetermined 5 mgN/L value (throughout the work), the control tanks showed much higher values. In the Brown Crab experiment the control had to be stopped after 2.3 days to avoid animal welfare issues, while the test completed the full 4.8 d. Yet, the crabs from the Test tanks exhibited much higher survival rates following 24 and 48 h dry packing. The results show unequivocally that the addition of Zn-HCF to wet transfer tanks can improve the vitality of the shipped animals, allow to extend the transfer periods and/or increase the shipment density.

The EU Interreg Project "ADRINET": Assessment of Well-Known and Emerging Pollutants in Seafood and Their Potential Effects for Food Safety.

Anthropogenic activities lead to the spread of chemicals and biological materials, including plastic waste, toxic metals, and pharmaceuticals, of which the impact on the Mediterranean Sea is of high concern. In this context, the EU Interreg Italy-Albania-Montenegro Project "ADRINET (Adriatic Network for Marine Ecosystem) _244" (2018-2020) arises. It aims to carry out biomonitoring campaigns in the main commercial interest of fish and cephalopod species, such as Sparus aurata, Dicentrarchus labrax, Sepia spp., and Loligo spp. sampled in three different subregions of the Mediterranean Sea. The presence of the main environmental contaminants, such as cadmium, microplastics, and antibiotics was investigated in these seafood samples. Contamination by cadmium and antibiotics in the seafood investigated in our study was negligible. However, a high value of microplastics was detected in the stomach and gut of Sparus aurata and Dicentrarchus labrax. Overall, even though the presence of microplastics needs to be investigated by further studies, the results confirmed that the environmental conditions of the three bays investigated by the ADRINET project partners (Italy, Albania, Montenegro) are positive and not affected by intensive anthropogenic activity.

Dietary Artemisia arborescens Supplementation Effects on Growth, Oxidative Status, and Immunity of Gilthead Seabream (Sparus aurata L.).

Fish infectious diseases are one of the main constraints of the aquaculture sector. The use of medicinal plants provides a sustainable way of protection using safe, eco-friendly compounds in a more cost-effective way of treatment, compared to antibiotics. The aim of the present study is the assessment of Artemisia arborescens (AA) feed-supplementation effects on gilthead seabream (Sparus aurata). Fish with an average initial body weight of 109.43 ± 3.81 g, were divided into two groups based on AA feed composition (A25 and A50). Following two months of ad libitum feeding, the effect of diets on fish weight and length were measured. Fish serum and mucus were analyzed for non-specific immune parameters (nitric oxide, lysozyme, myeloperoxidase, protease-/anti-protease activity, and complement), antibody responses, oxidative stress (cytochrome P450 1A1, metallothionein), and metabolism markers (total protein, alkaline phosphatase, and glucose). Expression levels of antioxidants (sod1, gpx1), cytokines (il-1b, il-10, tfgb1, and tnfa), hepcidin, and heat shock protein grp75 genes were measured in spleen samples. A results analysis indicated that A. arborescens use as a feed supplement has a compromised positive effect on the growth performance, immune response, and blood parameters of gilthead seabream. Overall, the suitability of A. arborescens as an efficient food supplement for gilthead seabream health improvement was investigated, setting the basis for its application assessment in Mediterranean aquaculture.

Mucosal affairs: glycosylation and expression changes of gill goblet cells and mucins in a fish-polyopisthocotylidan interaction.

Secreted mucins are highly O-glycosylated glycoproteins produced by goblet cells in mucosal epithelia. They constitute the protective viscous gel layer overlying the epithelia and are involved in pathogen recognition, adhesion and expulsion. The gill polyopisthocotylidan ectoparasite Sparicotyle chrysophrii, feeds on gilthead seabream (Sparus aurata) blood eliciting severe anemia. Control unexposed and recipient (R) gill samples of gilthead seabream experimentally infected with S. chrysophrii were obtained at six consecutive times (0, 11, 20, 32, 41, and 61 days post-exposure (dpe)). In histological samples, goblet cell numbers and their intensity of lectin labelling was registered. Expression of nine mucin genes (muc2, muc2a, muc2b, muc5a/c, muc4, muc13, muc18, muc19, imuc) and three regulatory factors involved in goblet cell differentiation (hes1, elf3, agr2) was studied by qPCR. In addition, differential expression of glycosyltransferases and glycosidases was analyzed in silico from previously obtained RNAseq datasets of S. chrysophrii-infected gilthead seabream gills with two different infection intensities. Increased goblet cell differentiation (up-regulated elf3 and agr2) leading to neutral goblet cell hyperplasia on gill lamellae of R fish gills was found from 32 dpe on, when adult parasite stages were first detected. At this time point, acute increased expression of both secreted (muc2a, muc2b, muc5a/c) and membrane-bound mucins (imuc, muc4, muc18) occurred in R gills. Mucins did not acidify during the course of infection, but their glycosylation pattern varied towards more complex glycoconjugates with sialylated, fucosylated and branched structures, according to lectin labelling and the shift of glycosyltransferase expression patterns. Gilthead seabream gill mucosal response against S. chrysophrii involved neutral mucus hypersecretion, which could contribute to worm expulsion and facilitate gas exchange to counterbalance parasite-induced hypoxia. Stress induced by the sparicotylosis condition seems to lead to changes in glycosylation characteristic of more structurally complex mucins.

Chitosan-based delivery of fish codon-optimised Caenorhabditis elegans FAT-1 and FAT-2 boosts EPA and DHA biosynthesis in Sparus aurata

AbstractOmega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) are essential fatty acids required in healthy balanced diets for humans. To induce sustained production of n-3 LC-PUFA in gilthead seabream (Sparus aurata), chitosan-tripolyphosphate (TPP) nanoparticles encapsulating plasmids expressing fish codon-optimised Caenorhabditis elegans FAT-1 and FAT-2 were intraperitoneally administered every 4 weeks (3 doses in total, each of 10 μg plasmid per g of body weight). Growth performance and metabolic effects of chitosan-TPP complexed with pSG5 (empty plasmid), pSG5-FAT-1, pSG5-FAT-2 and pSG5-FAT-1 + pSG5-FAT-2 were assessed 70 days post-treatment. Tissue distribution analysis showed high expression levels of fish codon-optimised FAT-1 and FAT-2 in the liver (&gt; 200-fold). Expression of fat-1 and fat-1 + fat-2 increased weight gain. Fatty acid methyl esters assay revealed that co-expression of fat-1 and fat-2 increased liver production and muscle accumulation of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and total n-3 LC-PUFA, while decreased the n-6/n-3 ratio. Co-expression of fat-1 and fat-2 downregulated srebf1 and genes encoding rate-limiting enzymes for de novo lipogenesis in the liver, leading to decreased circulating triglycerides and cholesterol. In contrast, FAT-2 and FAT-1 + FAT-2 upregulated hepatic hnf4a, nr1h3 and key enzymes in glycolysis and the pentose phosphate pathway. Our findings demonstrate for the first time efficient and sustained production of EPA and DHA in animals after long-term treatment with chitosan-TPP-DNA nanoparticles expressing FAT-1 and FAT-2, which enabled the production of functional fish rich in n-3 LC-PUFA for human consumption.

An inside out journey: biogenesis, ultrastructure and proteomic characterisation of the ectoparasitic flatworm Sparicotyle chrysophrii extracellular vesicles

BackgroundHelminth extracellular vesicles (EVs) are known to have a three-way communication function among parasitic helminths, their host and the host-associated microbiota. They are considered biological containers that may carry virulence factors, being therefore appealing as therapeutic and prophylactic target candidates. This study aims to describe and characterise EVs secreted by Sparicotyle chrysophrii (Polyopisthocotyla: Microcotylidae), a blood-feeding gill parasite of gilthead seabream (Sparus aurata), causing significant economic losses in Mediterranean aquaculture.MethodsTo identify proteins involved in extracellular vesicle biogenesis, genomic datasets from S. chrysophrii were mined in silico using known protein sequences from Clonorchis spp., Echinococcus spp., Fasciola spp., Fasciolopsis spp., Opisthorchis spp., Paragonimus spp. and Schistosoma spp. The location and ultrastructure of EVs were visualised by transmission electron microscopy after fixing adult S. chrysophrii specimens by high-pressure freezing and freeze substitution. EVs were isolated and purified from adult S. chrysophrii (n = 200) using a newly developed ultracentrifugation-size-exclusion chromatography protocol for Polyopisthocotyla, and EVs were characterised via nanoparticle tracking analysis and tandem mass spectrometry.ResultsFifty-nine proteins involved in EV biogenesis were identified in S. chrysophrii, and EVs compatible with ectosomes were observed in the syncytial layer of the haptoral region lining the clamps. The isolated and purified nanoparticles had a mean size of 251.8 nm and yielded 1.71 × 108 particles · mL−1. The protein composition analysis identified proteins related to peptide hydrolases, GTPases, EF-hand domain proteins, aerobic energy metabolism, anticoagulant/lipid-binding, haem detoxification, iron transport, EV biogenesis-related, vesicle-trafficking and other cytoskeletal-related proteins. Several identified proteins, such as leucyl and alanyl aminopeptidases, calpain, ferritin, dynein light chain, 14–3–3, heat shock protein 70, annexin, tubulin, glutathione S-transferase, superoxide dismutase, enolase and fructose-bisphosphate aldolase, have already been proposed as target candidates for therapeutic or prophylactic purposes.ConclusionsWe have unambiguously demonstrated for the first time to our knowledge the secretion of EVs by an ectoparasitic flatworm, inferring their biogenesis machinery at a genomic and transcriptomic level, and by identifying their location and protein composition. The identification of multiple therapeutic targets among EVs' protein repertoire provides opportunities for target-based drug discovery and vaccine development for the first time in Polyopisthocotyla (sensu Monogenea), and in a fish-ectoparasite model.Graphical

New Insights into Geometric Morphometry Applied to Fish Scales for Species Identification.

The possibility of quick and cheap recognition of a fish species from a single dermal scale would be interesting in a wide range of contexts. The methods of geometric morphometry appear to be quite promising, although wide studies comparing different approaches are lacking. We aimed to apply two methods of geometric morphometry, landmark-based and outline-based, on a dataset of scales from five different teleost species: Danio rerio, Dicentrarchus labrax, Mullus surmuletus, Sardina pilchardus, and Sparus aurata. For the landmark-based method the R library "geomorph" was used. Some issues about landmark selection and positioning were addressed and, for the first time on fish scales, an approach with both landmarks and semilandmarks was set up. For the outline-based method the R library "Momocs" was used. Despite the relatively low number of scales analyzed (from 11 to 81 for each species), both methods achieved quite good clustering of all the species. In particular, the landmark-based method used here gave generally higher R2 values in testing species clustering than the outline-based method, but it failed to distinguish between a few couples of species; on the other hand, the outline-based method seemed to catch the differences among all the couples except one. Larger datasets have the potential to achieve better results with outline-based geometric morphometry. This latter method, being free from the problem of recognizing and positioning landmarks, is also the most suitable for being automatized in future applications.

Insights into core molecular changes associated with metamorphosis in gilthead seabream larvae across diverse hatcheries

Early development is a critical period in fish aquaculture and is influenced by biotic and abiotic factors (e.g., temperature, feed) that can vary significantly between hatcheries, making it difficult to identify core factors determining quality. Many of the existing larval transcriptome studies are small-scale and occur under specific rearing conditions that do not mirror the diversity of larviculture practices at an industrial level. In the present transcriptome study, gilthead seabream at the larval to juvenile transition (metamorphosis) from several hatcheries in Europe (Greece, Italy, and France) were analysed in a large-scale RNA-seq study. The aim was to uncover the most significant molecular modifications occurring during metamorphosis, irrespective of differences in biotic or abiotic factors, to address knowledge gaps associated with critical early developmental stages under industrial hatchery conditions. Commonly modified gene transcripts between larval stages were identified based on the clustering of gene expression profiles of 25 gilthead seabream libraries from different hatcheries in a PCA analysis. When larvae at flexion were compared to larvae at mid-metamorphosis, 2243 differentially expressed genes (DEGs) were identified, and when larvae at early to mid-metamorphosis were compared to mid to late-metamorphosis, 2299 DEGs were identified. Comparative analysis across the developmental stages of gilthead seabream revealed genes of importance for the metamorphic transition and adaptation to rearing conditions, including genes related to the nervous system at flexion (24 days post hatch), enteroendocrine cell differentiation, and lipid homeostasis at early to mid-metamorphosis (46 dph), and enrichment of genes indicative of immune competence at mid to late-metamorphosis (51–54 dph). The differential expression of some endocrine-associated genes, dio1, dio2, cldn1, ing4, Pou3f4, and fgf22, highlights their importance in metamorphosis. Meta-analysis of the transcriptomes from two species, the gilthead seabream and Senegalese sole, that have differing symmetry and ecology uncovered common molecular expression patterns that underlie larvae maturation during metamorphosis, and we propose that these represent core gene markers of the metamorphosis in these two fish species.

Prevalence, genetic diversity, and antimicrobial susceptibility of Vibrio spp. infected gilthead sea breams from coastal farms at Damietta, Egypt

BackgroundVibriosis is one of the most serious bacterial diseases and causes high morbidity and mortality among cultured sea breams. This study was undertaken to track the surveillance of Vibrio infection and its correlation to environmental factors. A total of 115 gilthead sea breams were collected seasonally from a private earthen pond fish farm in the Shatta area of Damietta, Egypt from September 2022 to July 2023. Physicochemical parameters of water were analyzed, and heavy metal levels were measured. The fish samples were subjected to clinical, bacteriological, Enterobacterial Repetitive Intergenic Consensus (ERIC) fingerprinting, and hematoxylin and Eosin histopathological staining.ResultsThe results revealed significant variations in the water quality parameters over different seasons, in addition to an increase in heavy metals. Naturally infected fish showed external signs and postmortem lesions that were relevant to bacterial infection. Two dominant Vibrio subspecies of bacteria were identified: V. alginolyticus (205 isolates) and V. fluvialis (87 isolates). PCR confirmed the presence of V. alginolyticus using the species-specific primer collagenase at 737 bp. The highest prevalence of V. alginolyticus was detected during the summer season (57.72%), and the lowest prevalence was observed in autumn (39.75%). The correlation analysis revealed a positive relationship between V. alginolyticus and water temperature (r = 0.69). On the other hand, V. fluvialis showed a high prevalence during the autumn season (25.30%) and the lowest prevalence during the summer season (10.56%), where it was negatively correlated with water temperatures (r =—0.03). ERIC fingerprinting showed genetic variation within the Vibrio isolates. Antimicrobial susceptibility testing revealed sensitivity to ciprofloxacin and doxycycline, and resistance to amoxicillin and erythromycin. The multiple antibiotic resistance (MAR) index values for V. alginolyticus and V. fluvialis ranged from 0.3 to 0.7, with a multi-drug resistance pattern to at least three antibiotics. Histopathological alterations in the affected tissues revealed marked hemorrhage, vascular congestion, and hemosiderosis infiltration.ConclusionThis study provides insights into the potential propagation of waterborne diseases and antibiotic resistance in the environment. Ensuring that the environment does not serve as a reservoir for virulent and contagious Vibrio species is a critical concern for regional aquaculture industries. Therefore, we recommend implementing environmental context-specific monitoring and surveillance tools for microbial resistance.

Determination of Multiclass Antibiotics in Fish Muscle Using a QuEChERS-UHPLC-MS/MS Method.

The surging global demand for fish has increased aquaculture practices, where antibiotics have become indispensable to prevent diseases. However, the passive incorporation of these compounds into the diet may have adverse effects on human health. In this work, the QuEChERS method combined with ultra-high-performance liquid chromatography tandem mass spectrometry was applied for the determination of 10 multiclass antibiotics (5 quinolones, 2 sulfonamides, 2 diaminopyrimidines, and 1 macrolide) in muscle tissue of farmed fish (European sea bass and gilt-head sea bream). The applied method demonstrated acceptable recovery values, mostly between 70 and 120%, with limits of quantification of the method meeting the established EU maximum residue limits. The analysis of twenty fish samples in duplicate revealed that most antibiotics were not present, with the only exception of oxolinic acid and tilmicosin in European sea bass, which were below the limit of quantification of the method.

Comparative Parasitological Studies of Cultured Gilthead seabream, Sparus aurata, and European seabass, Dicentrarchus labrax, in Portuguese Fish Farms

Comparative Parasitological Studies of Cultured Gilthead seabream, Sparus aurata, and European seabass, Dicentrarchus labrax, in Portuguese Fish Farms

Re-evaluation of certain aspects of the EFSA Scientific Opinion of April 2010 on risk assessment of parasites in fishery products, based on new scientific data. Part 1: ToRs1-3.

Surveillance data published since 2010, although limited, showed that there is no evidence of zoonotic parasite infection in market quality Atlantic salmon, marine rainbow trout, gilthead seabream, turbot, meagre, Atlantic halibut, common carp and European catfish. No studies were found for greater amberjack, brown trout, African catfish, European eel and pikeperch. Anisakis pegreffii, A. simplex (s. s.) and Cryptocotyle lingua were found in European seabass, Atlantic bluefin tuna and/or cod, and Pseudamphistomum truncatum and Paracoenogonimus ovatus in tench, produced in open offshore cages or flow-through ponds or tanks. It is almost certain that fish produced in closed recirculating aquaculture systems (RAS) or flow-through facilities with filtered water intake and exclusively fed heat-treated feed are free of zoonotic parasites. Since the last EFSA opinion, the UV-press and artificial digestion methods have been developed into ISO standards to detect parasites in fish, while new UV-scanning, optical, molecular and OMICs technologies and methodologies have been developed for the detection, visualisation, isolation and/or identification of zoonotic parasites in fish. Freezing and heating continue to be the most efficient methods to kill parasites in fishery products. High-pressure processing may be suitable for some specific products. Pulsed electric field is a promising technology although further development is needed. Ultrasound treatments were not effective. Traditional dry salting of anchovies successfully inactivated Anisakis. Studies on other traditional processes - air-drying and double salting (brine salting plus dry salting) - suggest that anisakids are successfully inactivated, but more data covering these and other parasites in more fish species and products is required to determine if these processes are always effective. Marinade combinations with anchovies have not effectively inactivated anisakids. Natural products, essential oils and plant extracts, may kill parasites but safety and organoleptic data are lacking. Advanced processing techniques for intelligent gutting and trimming are being developed to remove parasites from fish.

Exploring the Integrated Role of miRNAs and lncRNAs in Regulating the Transcriptional Response to Amino Acids and Insulin-like Growth Factor 1 in Gilthead Sea Bream (Sparus aurata) Myoblasts.

In this study, gilthead sea bream (Sparus aurata) fast muscle myoblasts were stimulated with two pro-growth treatments, amino acids (AA) and insulin-like growth factor 1 (Igf-1), to analyze the transcriptional response of mRNAs, microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) and to explore their possible regulatory network using bioinformatic approaches. AA had a higher impact on transcription (1795 mRNAs changed) compared to Igf-1 (385 mRNAs changed). Both treatments stimulated the transcription of mRNAs related to muscle differentiation (GO:0042692) and sarcomere (GO:0030017), while AA strongly stimulated DNA replication and cell division (GO:0007049). Both pro-growth treatments altered the transcription of over 100 miRNAs, including muscle-specific miRNAs (myomiRs), such as miR-133a/b, miR-206, miR-499, miR-1, and miR-27a. Among 111 detected lncRNAs (>1 FPKM), only 30 were significantly changed by AA and 11 by Igf-1. Eight lncRNAs exhibited strong negative correlations with several mRNAs, suggesting a possible regulation, while 30 lncRNAs showed strong correlations and interactions with several miRNAs, suggesting a role as sponges. This work is the first step in the identification of the ncRNAs network controlling muscle development and growth in gilthead sea bream, pointing out potential regulatory mechanisms in response to pro-growth signals.

Impact of Hydroxytyrosol-Rich Extract Supplementation in a High-Fat Diet on Gilthead Sea Bream (Sparus aurata) Lipid Metabolism.

High-fat diets (HFDs) enhance fish growth by optimizing nutrient utilization (i.e., protein-sparing effect); however, their potential negative effects have also encouraged the search for feed additives. This work has investigated the effects of an extract rich in a polyphenolic antioxidant, hydroxytyrosol (HT), supplemented (0.52 g HT/kg feed) in a HFD (24% lipid) in gilthead sea bream (Sparus aurata). Fish received the diet at two ration levels, standard (3% of total fish weight) or restricted (40% reduction) for 8 weeks. Animals fed the supplemented diet at a standard ration had the lowest levels of plasma free fatty acids (4.28 ± 0.23 mg/dL versus 6.42 ± 0.47 in the non-supplemented group) and downregulated hepatic mRNA levels of lipid metabolism markers (ppara, pparb, lpl, fatp1, fabp1, acox1, lipe and lipa), supporting potential fat-lowering properties of this compound in the liver. Moreover, the same animals showed increased muscle lipid content and peroxidation (1.58- and 1.22-fold, respectively, compared to the fish without HT), suggesting the modulation of body adiposity distribution and an enhanced lipid oxidation rate in that tissue. Our findings emphasize the importance of considering this phytocompound as an optimal additive in HFDs for gilthead sea bream to improve overall fish health and condition.

Virulence and pangenome analysis of Vibrio harveyi strains from Greek and Red Sea marine aquaculture

Comparative genomic analysis of Vibrio harveyi, a leading pathogen in Mediterranean aquaculture, was conducted to assess the genomic plasticity of the species. V. harveyi is responsible for vibriosis outbreaks during the warmer months, resulting in significant economic losses that impact Greek aquaculture. Over a span of six years, we curated a diverse collection of bacterial strains associated with these outbreaks. Whole-genome sequencing was employed in 21 strains to uncover their evolutionary relationships and virulence factors. Pangenome analysis revealed significant gene gain/loss, with numerous unique genes within the strains. The core genome featured genes associated with pathogenicity, including secretion systems, flagella, pili, siderophores, and toxins. Furthermore, we examined the phenotypic traits and virulence of these strains using in vivo testing with gilthead seabream larvae. Our findings indicated variant metabolic profiles and virulence among the strains during these in vivo assays. By integrating genomic and phenotypic data, our study highlights the ongoing evolution of disease-associated V. harveyi strains, which pose a growing challenge to the aquaculture industry.