In vertebrates, the essential fatty acids (FA) that satisfy the dietary requirements for a given species depend upon its desaturation and elongation capabilities to convert the C18 polyunsaturated fatty acids (PUFA), namely linoleic acid (LA, and α-linolenic acid (ALA, 18:3n-3), into the biologically active long-chain (C20-24) polyunsaturated fatty acids (LC-PUFA), including arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). Recent studies have established that tambaqui (Colossoma macropomum), an important aquaculture-produced species in Brazil, is a herbivorous fish that can fulfil its essential FA requirements with dietary provision C18 PUFA LA and ALA, although the molecular mechanisms underpinning such ability remained unclear. The present study aimed at cloning and functionally characterizing genes encoding key desaturase and elongase enzymes, namely fads2, elovl5 and elovl2, involved in the LC-PUFA biosynthetic pathways in tambaqui.First, a fads2-like desaturase was isolated from tambaqui. When expressed in yeast, the tambaqui Fads2 showed Δ6, Δ5 and Δ8 desaturase capacities within the same enzyme, enabling all desaturation reactions required for ARA, EPA and DHA biosynthesis.Moreover, tambaqui possesses two elongases that are bona fide orthologs of elovl5 and elovl2. Their functional characterization confirmed that they can operate towards a variety of PUFA substrates with chain lengths ranging from 18 to 22 carbons. Overall our results provide compelling evidence that demonstrates that all the desaturase and elongase activities required to convert LA and ALA into ARA, EPA and DHA are present in tambaqui within the three genes studied herein, i.e. fads2, elovl5 and elovl2.

Clupeiformes, such as sardines and herrings, represent an important share of worldwide fisheries. Among those, the European sardine (Sardina pilchardus, Walbaum 1792) exhibits significant commercial relevance. While the last decade showed a steady and sharp decline in capture levels, recent advances in culture husbandry represent promising research avenues. Yet, the complete absence of genomic resources from sardine imposes a severe bottleneck to understand its physiological and ecological requirements. We generated 69 Gbp of paired-end reads using Illumina HiSeq X Ten and assembled a draft genome assembly with an N50 scaffold length of 25,579 bp and BUSCO completeness of 82.1% (Actinopterygii). The estimated size of the genome ranges between 655 and 850 Mb. Additionally, we generated a relatively high-level liver transcriptome. To deliver a proof of principle of the value of this dataset, we established the presence and function of enzymes (Elovl2, Elovl5, and Fads2) that have pivotal roles in the biosynthesis of long chain polyunsaturated fatty acids, essential nutrients particularly abundant in oily fish such as sardines. Our study provides the first omics dataset from a valuable economic marine teleost species, the European sardine, representing an essential resource for their effective conservation, management, and sustainable exploitation.

European seabass (Dicentrarchus labrax) production is often hampered by bacterial infections such as photobacteriosis caused by Photobacterium damselae subsp. piscicida (Phdp). Since diet can impact fish immunity, this work investigated the effect of dietary supplementation of 5% Gracilaria sp. aqueous extract (GRA) on seabass antioxidant capacity and resistance against Phdp. After infection, mortality was delayed in fish fed GRA, which also revealed increased lysozyme activity levels, as well as decreased lipid peroxidation, suggesting higher antioxidant capacity than in fish fed a control diet. Dietary GRA induced a down-regulation of hepatic stress-responsive heat shock proteins (grp-78, grp-170, grp-94, grp-75), while bacterial infection caused a down-regulation in antioxidant genes (prdx4 and mn-sod). Diet and infection interaction down-regulated the transcription levels of genes associated with oxidative stress response (prdx5 and gpx4) in liver. In head-kidney, GRA led to an up-regulation of genes associated with inflammation (il34, ccr9, cd33) and a down-regulation of genes related to cytokine signalling (mif, il1b, defb, a2m, myd88). Additionally, bacterial infection up-regulated immunoglobulins production (IgMs) and down-regulated the transcription of the antimicrobial peptide leap2 in head kidney. Overall, we found that GRA supplementation modulated seabass resistance to Phdp infection.

-The study evaluated the replacement of bovine heart by gelatin in the feed training of carnivorous fish, using giant trahira (Hoplias lacerdae) as an experimental model. A completely randomized design with four treatments and five repetitions was employed. The treatments were composed of wet ingredients beef heart (control), gelatin diluted in water, gelatin diluted in beef heart broth, and gelatin diluted in water mixed with fish meal. The fish (3.22±0.03 cm and 0.57±0.01 g) were conditioned to accept industrialized diets by the technique of gradual feed ingredients transition in the diet. Gains in weight and length, efficiency of feed training, specific growth rate, cannibalism, mortality and survival rates were evaluated. There was significant difference in weight and length gains and specific growth rate, whereby the use of bovine heart gave the best results. Greater efficiency of feed training was observed for fish fed diets containing beef heart and gelatin diluted in water mixed with fish meal. The high survival rates and the absence of significant differences among treatments for rates of cannibalism, mortality and survival indicate the feasibility of using gelatin as a moist ingredient in the feed training of carnivorous fish.

This study aimed to evaluate the effect of different proportions of soybean and linseed oil to replace fish oil in diets for female lambari (Astyanax altiparanae). A completely randomized design with seven treatments and five replicates was used. The treatments consisted of a diet containing fish oil and six diets containing different proportions of soybean oil (S) and linseed oil (L), 10S/0L, 8S/2L, 6S/4L, 4S/6L, 2S/8L and 0S/10L. The fish that received the highest proportion of linseed oil (0S/10L) had the lowest crude lipid in their carcasses. The highest linolenic acid (18:3n3) concentrations were detected in the carcasses of fish fed diets with high proportions of linseed oil (4S/6L, 2S/8L, and 0S/10L). The highest n6/n3 ratios corresponded to the carcasses of fish fed diets containing the lowest proportions of linseed oil (10S/0L and 8S/2L). The highest levels of 20:5n3 (eicosapentaenoic acid [EPA]), 22:6n3 (docosahexaenoic acid [DHA]) and EPA+DHA occurred in fish fed diets containing fish oil. Among the fish that received diets with vegetable oils, the EPA+DHA was higher in the fish of the treatments 4S/6L, 2S/8L and 0S/10L. Diets supplemented with a 4S/6L proportion provide adequate deposition of the n3 fatty acids series in the lambari carcass.

The teleost fish tambaqui, Colossoma macropomum , is a valuable resource for the Brazillian aquaculture sector, representing more than one-quarter of the total production. In this context, the development of molecular tools is paramount to address and improve productivity, nutrition, and genetic breeding programs. In this study, we applied RNA-seq technology to produce the first comprehensive liver transcriptome in this species. Our analysis generated a gold standard transcriptome with a total of 43,098 transcripts, with an N50 of 1855 bp and the average length of 1312 bp. To functionally annotate the transcripts, the Trinotate pipeline together with several public databases were scrutinized. The blast-x analysis revealed more than 40,000 homologous match hits for each database (NCBI-Nr, Uniref90, Swissprot, Trembl), while the Kaas web server allowed the mapping of our transcripts to 380 kegg pathways. The dataset provided in this study entails a comprehensive molecular resource, which will be instrumental to further develop tambaqui aquaculture, specifically in the field of nutrigenomics.

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The aim of this study was to evaluate commercial gelatin in the total replacement of bovine heart in feed training of "pacamã" Lophiosilurus alexandri in different water salinities. A completely randomized experimental design, in a 2 × 3 factorial arrangement, was performed using two types of moist ingredients (bovine heart and gelatin) and three water salinities (0.0; 2.0 and 4.0 g of salt L -1 ) with three replications.Juveniles (2.39 ± 0.08 cm standard length and 0.20 ± 0.03 g of weight) were conditioned to accept commercial diets by the technique of the gradual transition of ingredients. At the end of 36 days no differences were observed to weight gain, length gain and specific growth rate. The feed training efficiency was better (P < 0.05) with the gelatin use, 100.0%. There was a negative effect of salinity on the survival rate and management efficiency in the concentration of 4 g of salt L -1 , with values of 58.6 ± 12.0 % and 58.0 ± 12.0 %, respectively. Lophiosilurus alexandri juveniles could be feed-trained to accept commercial diets with gelatin in the total replacement of bovine heart in freshwater or salinity of 2 g of salt L -1 .