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The growth and consolidation of the gilthead seabream ( Sparus aurata) industry require improvement based on permanent and cumulative aspects, such as those derived from genetic breeding programmes. Marker Assisted Selection ( MAS) by Quantitative Trait Loci ( QTL) can be usefully implemented with the appropriate tools. In this study, 138 microsatellite markers from the genetic map of gilthead seabream were redesigned to be amplified under the same PCR conditions. A final set of 13 multiplex PCRs (named ReM sa) with 106 of these markers was developed to cover 100% of the linkage groups. These effective multiplex PCRs enable to optimize QTL searching with a critical reduction in costs and errors. Results showed that the mean value of the number of alleles for 106 markers was 6.9. The mean observed heterozygosity ranged from 0.53 to 0.86, and 74.5% of markers were highly informative according to their polymorphic information content. The correct inheritance and segregation of alleles of each locus was confirmed after genotyping 62 individuals of a full-sib family by these multiplex PCRs. In addition, genetic features of the 20 microsatellite markers that worked correctly but were not included in any multiplex PCR are also reported to provide geneticists with the possibility of including them in more comprehensive screening studies. [ABSTRACT FROM AUTHOR]

The effect of controlled flushing on natural phytoplankton communities in brackish estuarine water ponds of Doñana Natural Park (Guadalquivir marshes, SW Spain) was evaluated throughout a year cycle by 16S chloroplast rDNA metagenome analysis. Multivariate analysis of phytoplankton assemblages based on the abundance of 30 main identified microalgae included in seven different phyla revealed pond flushing accounted for 19.6% of total data variation, a value far below the 42.5% variability explained by seasonality. Microalgae species biovolume was a better descriptor explaining phytoplankton assemblages in comparison to species relative abundance. Increasing pond flushing led to augmented phytoplankton diversity in spring, summer and autumn, but not in winter. Diatoms were more abundant under high water flushing, a situation that favoured the tychopelagic behaviour of some species. Cyanobacteria and dinophytes were more abundant under low flushing. Haptophytes and cryptophytes relative biomass was also enhanced by low water flushing, but only during winter and spring. Two main haptophytes that seasonally succeeded each other exhibited opposed response to hydrology with Isochrysis sp. showing negative response to increased flushing and Diacronema vlkianum showing a positive reaction. Both species represented a permanent and relevant haptophytes contribution to phytoplankton assemblages in marsh ponds previously undescribed in the area. [ABSTRACT FROM AUTHOR]

Uptake of iodide was studied in the marine microalga Isochrysis sp. (isol. Haines, T. ISO) during short-term incubations with radioactive iodide (125I−). Typical inhibitors of the sodium/iodide symporter ( NIS) did not inhibit iodide uptake, suggesting that iodide is not taken up through this transport protein, as is the case in most vertebrate animals. Oxidation of iodide was found to be an essential step for its uptake by T. ISO and it seemed likely that hypoiodous acid ( HOI) was the form of iodine taken up. Uptake of iodide was inhibited by the addition of thiourea and of other reducing agents, like L-ascorbic acid, L-glutathione and L-cysteine and increased after the addition of oxidized forms of the transition metals Fe and Mn. The simultaneous addition of both hydrogen peroxide ( H2O2) and a known iodide-oxidizing myeloperoxidase ( MPO) significantly increased iodine uptake, but the addition of H2O2 or MPO separately, had no effect on uptake. This confirms the observation that iodide is oxidized prior to uptake, but it puts into doubt the involvement of H2O2 excretion and membrane-bound or extracellular haloperoxidase activity of T. ISO. The increase of iodide uptake by T. ISO upon Fe(III) addition suggests the nonenzymatic oxidation of iodide by Fe(III) in a redox reaction and subsequent influx of HOI. This is the first report on the mechanism of iodide uptake in a marine microalga. [ABSTRACT FROM AUTHOR]

The meagre ( Argyrosomus regius) is a commercially important species for fisheries, and aquaculture production has been increasing in recent years. However, this growing importance has not been matched by increased genetic knowledge of the species. For this reason, an initial approach has been made to understanding the genetics of the meagre, using three particular multigene families (45 S and 5 S ribosomal DNA and U2 sn RNA gene) as both molecular and cytogenetic markers. Only one type of 5 S rDNA and only one ITS-1 (from 45 S rDNA) were obtained, and these therefore could provide the basis for the development of genetic markers for this species. However, the U2 sn RNA gene produced a multi-band electrophoretic pattern, and some of these bands were demonstrated to be linked with the U1 sn RNA gene. This linkage could also provide a good species-specific marker which could be useful for tracing the evolutionary history of the Sciaenidae family. In this study, we have described for the first time the karyotype of the meagre: this is composed of 48 acrocentric chromosomes. Each of the three gene families were localized on different chromosome pairs, although the U2 sn RNA gene probe was also located scattered throughout the genome of the meagre, as expected by the amplification pattern. [ABSTRACT FROM AUTHOR]

To study the substitution of fish oil by vegetable oils in fish diets, juveniles Senegalese sole ( Solea senegalensis) were fed diets (56 % crude protein, 12 % crude lipid) containing either linseed (100LO) or soybean (100SO) oils in comparison with a 100 % fish oil-based diet (100FO) for 90 days. Samples of muscle, liver, and intestine were collected for biochemical analysis and for glucocorticoid receptor-related genes, including GR1 and GR2, and the associated heat shock proteins HSP70, HSP90AA, and HSP90AB. Besides, basal levels of plasma cortisol were also determined. After the feeding period, a stress test, consisting on 5 min of net chasing, was applied to a selected population of each dietary group. Total replacement of fish oil by vegetable oils did not induced changes in fish growth and performance, but affected fatty acid profile of muscle, liver, and intestine, reflecting those tissues the characteristic fatty acids of each type of dietary oil. A tendency to conserve the ARA/EPA ratio could be observed in the different tissues, despite of the level of these fatty acids in diet. Chasing stress induced an increase of muscle GR1 and a reduction in intestinal GR2 relative expressions at any of the experimental diets assayed. In liver, chasing stress induced an increase in both GR1 and GR2 gene expression in fish fed fish oil diets. Similarly, chasing stress induced an increase of muscle HSP70 and decrease of HSP90AB in liver at any of the experimental diet assayed. Besides, vegetable oils decreased the expression of HSP70 in intestine, being the relative expression of liver HSP90AA increased by the inclusion of linseed oil in the diet, at any of the experimental conditions assayed. [ABSTRACT FROM AUTHOR]

There has been considerable discussion in recent years on the evolution of the tandemly repeated multigene families, since some organisms show a concerted model whereas others show a birth-and-death model. This controversial subject extends to several species of fish. In this study, three species of the Sparidae family ( Pagrus pagrus, P. auriga and Diplodus sargus) and an interspecific hybrid ( P. pagrus (♀) × P. auriga (♂)) have been studied at both molecular and cytogenetic level, taking three different multigene families (5S rDNA, 45S rDNA and U2 snDNA). Results obtained with the 5S rDNA in P. pagrus and P. auriga are characterized by a considerable degree of conservation at the two levels; however, an extraordinary variation was observed in D. sargus at the two levels, which has never been found in other fishes studied to date. As a consequence of this, the evolutionary model of the multigene families is discussed considering the results obtained and others from the bibliography. The result obtained in the hybrid allowed the recombination frequency in each multigene family to be estimated. [ABSTRACT FROM AUTHOR]

This article discusses a study which examined the toxicity of different Photobacterium damselae subspecies damselae strains isolated from cultured diseased fish. The study conducted in vivo and in vitro assays using bacterial cultures and their extracellular products (ECPs). It also made a comparison of the enzymatic activities of the products with their cyto toxicity in fish and mammalian cell lines. The study suggested the relationship of the virulence of the strain with the hemolytic activity or with the production of the toxin damselysin.

The article presents a study which examined the role of Vibrio harveyi for the development of vibriosis in cultured wedge sole Dicologoglossa cuneata, flatfish species from the Family Soleidae. For the study, a virulence test of the isolated Vibrio harveyi was conducted using fry and juvenile wedge sole. Researchers found that all isolates have some of the characteristics in Vibrio harveyi descriptions like the ability to hydrolyze aesculin. They also found that lack of susceptability of wedge sole to bath immersion could possibly be linked to the absence of other determining factors like skin lesions and infections.

Abstract: Thyroid hormones (THs) play a key role in larval development, growth and metamorphosis in flatfish. Their genomic effects are mediated by thyroid hormone receptors (TRs). In this study, cDNAs encoding for TRαA, TRαB, and TRβ have been sequenced in Senegalese sole (Solea senegalensis). Main domains and conserved motifs were identified. Also, a truncated TRαB isoform (referred to as TRαBtr) and a spliced TRβ variant (referred to as TRβv) were detected. A phylogenetic analysis grouped both TRα and TRβ genes into two separate clusters with their fish and mammalian counterparts. Expression profiles during larval development and in juvenile tissues were analyzed using a real-time PCR approach. In juvenile fish, TRαA, TRαB, TRβv, and TRβ showed distinct transcript levels in tissues. During metamorphosis, only TRβv and TRβ modified their mRNA levels in a similar way to the T4 contents. To evaluate the possible regulation of TRs by their cognate ligand T4 during sole metamorphosis, larvae were exposed to the goitrogen thiourea (TU). TRβ transcripts decreased significantly at 11 and 15 days after treatment. Moreover, adding exogenous T4 hormone to TU-treated larvae restored the steady-state levels or even increased TRβ and TRβv mRNAs with respect to the untreated control. Overall, these results demonstrate that TRβ transcription is up-regulated by THs playing a major role during metamorphosis in Senegalese sole. [Copyright &y& Elsevier]

Ribosomal proteins (RPs) comprise a large set of highly evolutionarily conserved proteins that are often over-represented in complementary DNA libraries. They have become very useful markers in comparative genomics, genome evolution, and phylogenetic studies across taxa. In this study, we report the sequences of the complete set of 60S RPs in Senegalese sole ( Solea senegalensis) and Atlantic halibut ( Hippoglossus hippoglossus), two commercially important flatfish species. Amino-acid sequence comparisons of the encoded proteins showed a high similarity both between these two flatfish species and with respect to other fish and human counterparts. Expressed sequence tag analysis revealed the existence of paralogous genes for RPL3, RPL7, RPL41, and RPLP2 in Atlantic halibut and RPL13a in Senegalese sole as well as RPL19 and RPL22 in both species. Phylogenetic analysis of paralogs revealed distinct evolutionary histories for each RP in agreement with three rounds of genome duplications and lineage-specific duplications during flatfish evolution. Steady-state transcript levels for RPL19 and RPL22 RPs were quantitated during larval development and in different tissues of sole and halibut using a real-time polymerase chain reaction approach. All paralogs were expressed ubiquitously although at different levels in different tissues. Most RP transcripts increased coordinately after larval first-feeding in both species but decreased progressively during the metamorphic process. In all cases, expression profiles and transcript levels of orthologous genes in Senegalese sole and Atlantic halibut were highly congruent. The genomic resources and knowledge developed in this survey will be useful for the study of Pleuronectiformes evolution. [ABSTRACT FROM AUTHOR]

The complete mitochondrial DNA sequence of the frigate tuna Auxis thazard and two divergent mitotypes (Mitotype I and Mitotype II) of the bullet tuna Auxis rochei have been determined. The total length of the mitogenomes was 16,506, 16,501 and 16,503 bp, respectively. All mitogenomes had a gene content (13 protein-coding, 2 rRNAs and 22 tRNAs) and organization similar to those observed in most other vertebrates. The major non-coding region (control region) ranged between 843 and 847 bp in length, and showed the typical conserved blocks. Phylogenetic analyses revealed a monophyletic origin of Auxis with respect to other tuna fish. Molecular data here presented provide a useful tool for evolutionary as well as population genetic studies. [ABSTRACT FROM AUTHOR]