RESUMO

We evaluated the growth performance of pacu and tambaqui and their reciprocal hybrids (tambacu and paqui) under different feeding programs. We raised 30 individuals from each species and their respective crosses, distributing them into three replicate cages with 10 individuals each. Throughout the 5-month experimental period, the fish were weighed six times while exposed to diverse feeding regimens involving three commercial diets with varying combinations of crude protein (CP) levels: 24%, 28%, and 32%. Growth curves were adjusted using nonlinear models. The evaluation period was insufficient for adjusting the logistic model for the tambaqui and paqui treatments with the highest initial protein intake. Pure pacu had a higher (p < 0.05) growth rate (k = 0.0185) than in the tambacu hybrid (k = 0.0134) and proved to have an early performance since animals from this group reached their weight at inflection faster. Despite growing more slowly, tambacu reached a higher (p < 0.05) final weight (A = 1137.12) than in the pacu (A = 889.12). Among the feeding programs, animals that received less CP showed greater growth potential; however, longer evaluation is important to verify if the initial CP intake has no significant positive effect on fish growth.

Assuntos

RESUMO

Satellite DNAs (satDNAs) are tandemly repeated sequences that are usually located on the heterochromatin, and the entire collection of satDNAs within a genome is called satellitome. Primarily, these sequences are not under selective pressure and evolve by concerted evolution, resulting in elevated rates of divergence between the satDNA profiles of reproductive isolated species/populations. Here, we characterized two additional satellitomes of Characiformes fish (Colossoma macropomum and Piaractus mesopotamicus) that diverged approximately 30 million years ago, while still retaining conserved karyotype features. The results we obtained indicated that several satDNAs (50% of satellite sequences in P. mesopotamicus and 43% in C. macropomum) show levels of conservation between the analyzed species, in the nucleotide and chromosomal levels. We propose that long-life cycles and few genomic changes could slow down rates of satDNA differentiation.

Assuntos

RESUMO

B chromosomes are additional dispensable elements to the standard chromosomal set of an organism. In most cases, their transmission differs from Mendelian patterns, leading to their accumulation or extinction. The present study aimed to describe, for the first time, the transmission pattern of B chromosome in a population of Psalidodon paranae through directed crosses, as well as to analyze the populational dynamics of B chromosome. Our results revealed the possible elimination of B chromosome in crossings where only females were B-carriers, with a mean transmission rate (kB) of 0.149; however, kB was significantly higher in crossings involving male B-carriers (kB = 0.328-0.450). Moreover, we observed an increase in the frequency of B chromosomes in the natural population of P. paranae in the last two decades. These apparently contradictory results can make sense if the B chromosome provides adaptive advantages to their carriers. Here, we observed a differential transmission of B chromosomes in each sex of parental individuals, with higher transmission rates in crossing involving males B-carriers, in addition to describe the temporal changes of B chromosome frequency in P. paranae.

Assuntos

RESUMO

The identification of fish species using traditional methods is generally based only on morphological characteristics and these methods are currently under review. This kind of identification of hybrid fishes solely based on their morphologies may be unreliable, especially when the samples include juveniles and post-F1 lineage fishes. Therefore, in the present study, we used molecular markers to accurately identify the fish species of economic interest that are used as materials in the projects developed in research institutions. We evaluated six lots of fishes sampled from different research centers, containing a total of 84 specimens acquired from private fish farms that were considered to be the representatives of pure species. Genetic analyses of all the specimens revealed that, globally, 22 samples (26.2%) were interspecific hybrids, while 20 (90.9%) samples were surprisingly characterized as post-F1 hybrids. This result confirms that hybrids are sold in markets without adequate labeling and also indicates the lack of proper control of the commercialization and management of stocks and products in fish farms. In addition, we determined that molecular diagnosis was an extremely effective and necessary method to test the reliability of biological materials currently used in scientific research.

RESUMO

Tambaqui Colossoma macropomum is the most cultivated native fish in South America and Aeromonas hydrophila is one of the main bacteria infecting tropical fish. Despite the economic importance of this round fish, to date, there has been a paucity of investigations into haematological changes in tambaqui. In this study, detailed blood analyses (0 h, 6 h, 24 h, 7 d and 14 d) following intraperitoneal challenge with A. hydrophila were performed. After analysing the results, there was a suspicion of a novel cell death mechanism via extracellular traps (ETosis) in tambaqui. The search for ETosis was based on differential interference contrast (DIC) microscopy and scanning electron microscopy (SEM) assays through application of an adapted protocol applying co-incubation of leukocytes with A. hydrophila. The cells were investigated at: 0 h (control), 4 h and 7 h after incubation. The complete haemogram profile showed an uncommon severe leukopenia in early phases of infection (6 h, p < 0.001 and ≤ 0.05), due to significant decreases in the three main leukocytes: lymphocytes (6 h, p ≤ 0.001), monocytes (6 h, p ≤ 0.05) and neutrophils (6 h and 24 h, p ≤ 0.01 and p ≤ 0.05). Leucocytosis and lymphocytosis (p ≤ 0.01) were ascertained only 7 days post-infection. Through DIC and SEM, we discovered that leukocyte suicide exposed the nuclear contents between 4 and 7 h after stimuli with bacteria. The leukogram profile associated with DIC and SEM analyses suggested that tambaqui leukocytes underwent a programmed death (ETosis) in order to expose chromatin and granule proteins as a trap to bind and then kill bacteria; thus, preventing A. hydrophila from spreading and resulting in leukopenia during the early phase of bacterial infection. In this paper, we presume that ETosis is one of the last resources for tambaqui to contain the infection, and after this leukocyte strategy, a high number of phagocytic cells are produced and released into the peripheral circulation.

Assuntos

RESUMO

Tambaqui Colossoma macropomum is the most produced native fish in South America. Besides the lack of knowledge regarding bacteria-stricken diseases, the unappropriated using of off-label therapies are common. In this study, Aeromonas hydrophila pathogenicity for tambaqui was first established by Koch's Postulate. Lethal doses (LD) were settled for investigation of clinical signs and mortality. The antimicrobial activities were investigated by disk-diffusion test against 11 antibiotics and by broth microdilution methods against 3 antibiotics, 7 disinfectants and 11 herbal medicines. LD experiment showed up to 80% of fish mortality, skin darkness, ulcers, hemorrhage, lethargy and hypo/anorexia in all groups, with exception of control. The LD10,50,90 and 99 were established in 4.1 × 107, 8.8 × 107, 1.9 × 108 e 3.6 × 108 CFU/mL, respectively. Ceftriaxone, florfenicol, oxytetracycline and thiamphenicol were considered promising against A. hydrophila. All herbal medicines were classified as bactericides, but clove Eugenia caryophyllata and cinnamon Cinnamomum zeylanicum displayed strongest activities. Among disinfectants, malachite green was the only that did not present acceptable values, discouraging its use. In conclusion, Koch's postulate was fulfilled and tambaqui entered to the vast list of A. hydrophila hosts and promising results of chemical substances were provided, contributing to motile Aeromonas septicemia (MAS) control.

Assuntos

RESUMO

Pacu (Piaractus mesopotamicus) is a Neotropical fish of major importance for South American aquaculture. Septicemia caused by Aeromonas hydrophila bacteria is currently considered a substantial threat for pacu aquaculture that have provoked infectious disease outbreaks with high economic losses. The understanding of molecular aspects on progress of A. hydrophila infection and pacu immune response is scarce, which have limited the development of genomic selection for resistance to this infection. The present study aimed to generate information on transcriptome of pacu in face of A. hydrophila infection, and compare the transcriptomic responses between two groups of time-series belonging to a disease resistance challenge, peak mortality (HM) and mortality plateau (PM) groups of individuals. Nine RNA sequencing (RNA-Seq) libraries were prepared from liver tissue of challenged individuals, generating ∼160 million 150 bp pair-end reads. After quality trimming/cleanup, these reads were assembled de novo generating 211,259 contigs. When the expression of genes from individuals of HM group were compared to individuals from control group, a total of 4,413 differentially expressed transcripts were found (2,000 upregulated and 2,413 downregulated candidate genes). Additionally, 433 transcripts were differentially expressed when individuals from MP group were compared with those in the control group (155 upregulated and 278 downregulated candidate genes). The resulting differentially expressed transcripts were clustered into the following functional categories: cytokines and signaling, epithelial protection, antigen processing and presentation, apoptosis, phagocytosis, complement system cascades and pattern recognition receptors. The proposed results revealing relevant differential gene expression on HM and PM groups which will contribute to a better understanding of the molecular defense mechanisms during A. hydrophila infection.

RESUMO

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

RESUMO

The pacu (Piaractus mesopotamicus) is a Neotropical fish with remarkable productive performance for aquaculture. Knowledge of genetic resources in Neotropical fish is essential for their applications in breeding programs. The aim of this study was to characterize the genetic diversity of seven farmed populations of pacu which will constitute the basis for a broodstock foundation for coming breeding programs in Brazil. Analysis of one wild population (Paraná River) was used as a reference to compare genetic parameters in the farmed populations. The analyses were performed using 32 single-nucleotide polymorphisms (SNP) and 8 simple sequence repeat (SSR) markers. No significant differences in genetic diversity between populations estimated through the number of alleles and allelic richness, observed heterozygosity, expected heterozygosity, and minimum allele frequency were detected (p > 0.05). Low genetic diversity was observed in all farmed stocks and the wild population. Moreover, we detected low genetic structure when comparing farmed and wild populations for SNPs (FST = 0.07; K = 3) and SSRs (FST = 0.08; K = 2). Analysis of molecular variance (AMOVA) demonstrated that genetic variation was mostly within populations. Kinship analysis showed that most fish farms included related individuals at a proportion of at least 25%. Our results suggest that the basal broodstock for pacu breeding programs should be founded with individuals from different fish farms for higher genetic diversity and to avoid inbreeding risks.

Assuntos

RESUMO

The accumulation of repetitive DNA sequences on the sex-limited W or Y chromosomes is a well-known process that is likely triggered by the suppression of recombination between the sex chromosomes, which leads to major differences in their sizes and genetic content. Here, we report an analysis conducted on the satellitome of Megaleporinus macrocephalus that focuses specifically on the satDNAs that have been shown to have higher abundances in females and are putatively located on the W chromosome in this species. We characterized 164 satellite families in M. macrocephalus, which is, by far, the most satellite-rich species discovered to date. Subsequently, we mapped 30 satellites, 22 of which were located on the W chromosome, and 14 were shown to exist only on the W chromosome. Finally, we report two simple, quick and reliable methods that can be used for sex identification in M. macrocephalus individuals using fin clips or scales, which could be applicable to future studies conducted in the field of aquaculture.

Assuntos