Sheila Nogueira de Oliveira

Associação entre características de desempenho de tilápia-do-nilo ao longo do período de cultivo

The objective of this work was to estimate the structure and heritability of genetic correlations between the performance traits of Nile tilapia (Oreochromis niloticus) of the GIFT lineage during different stages of the production cycle. The Nile tilapias were grown in net cages. Daily total weight gain, live weight, and daily weight gain were measured in four periods, in approximately 30-day intervals. One-trait analyses were performed for all biometric measurements, and, in the two-trait analyses, measurements of the same traits were combined in pairs and to daily total weight gain. Estimated heritabilities ranged from 0.15 to 0.11 for live weight, from 0.16 to 0.09 for daily weight gain, and from 0.17 to 0.12 for daily total weight gain in the one-trait analyses. Estimated values of genetic correlation for live weight and daily weight gain, associated with daily total weight gain, ranged from 0.37 to 0.98 and from 0.74 to 0.88, respectively. The high genetic correlation estimated between live weight in intermediate biometric measurements and daily total weight gain suggests that selection for growth rate may be performed earlier.

Genetic parameters and trends of morphometric traits of GIFT tilapia under selection for weight gain

The main factor considered in breeding programs for fish is growth, which can be assessed in terms of a gain in either weight or body measurements. This study was undertaken to evaluate the morphometric traits of GIFT strain tilapia (Oreochromis sp.) selected for weight gain. The data set used contained information on 6,650 animals. The genetic values of 8,590 animals in a relationship matrix of five generations were predicted. The following morphometric measurements were evaluated: standard length; body depth and body width. Body area and volume were also calculated. Bi-character analyses involving morphometric traits were used to estimate (co)variance components. Heritability, larval and fingerling common environmental effects were estimated for each trait, together with the genetic and phenotypic correlations between traits. Bayesian procedures were utilised by Gibbs chains, and the convergence of the chains was tested using the Heidelberger and Welch method. Genetic trends were estimated by segmented regression of the fish breeding values of the generations considered in this study. Estimates of heritability (0.28 a 0.31) had moderate to high magnitudes for all traits. Genetic correlations between traits were all above 0.8, and the genetic gains were satisfactory from the third generation onwards. From the estimates of the genetic parameters and genetic gain the morphometric traits evaluated have good potential for selection.

Resposta à seleção de características de desempenho e morfométricas de tilápia-do-nilo ao longo do período de cultivo

The objective of this work was to study the selection response for performance and morphometrics traits in Nile tilapias (Oreochromis niloticus) in different measurements of farming. The one-trait analysis was performed for all traits studied and the two-traits analysis, were associated with the daily total weight gain in four measurement among performance and morphometrics traits in the fourth measurement. The heritabilities estimated for live weight, height and head length were higher in one-trait analysis than two-traits analysis. The genetic correlations, phenotypic, Pearson and Spearman among weight gain and all other measurements were higher along the farming. The indirect response was estimated at over 87% of direct response, which indicates that the selection may be performed early, using the daily total weight gain as selection criteria in intermediate measurement, without significant losses in genetic gain and contributing to reduction of cost production.

Avaliação genética de características morfométricas em tilápias do Nilo cultivadas

Breeding values, the differences in responses to selection, the (co)variance components and genetic parameters of the morphometrics traits of Nile tilapia (O. niloticus) reared in cages were estimated. Morphometric and performance traits of 1824 animals were analyzed. The estimated heritability ranged from 0,08541 to 0,194 and the proportion of the variation due common environ-mental/hatchery and nursery effects ranged from 0,07402 to 0,1586 and 0,00087 to 0,079, respectively. The values of genetic correlations and ranking indicated a strong association between genetic traits. The largest genetic gains were for weight and daily weight gain, and the best response to indirect selection was checked for weight. Selection for growth rate led to genetic gain in morphometric traits.

Diversidad genética de Piaractus mesopotamicus utilizado en programas de repoblación

Nowadays it has been verified the decrease and the disappearance of many fish species in several aquatic environments in the Brazil. As form of minimizing that impact, stocking programs come being used with more intensity, meantime, little importance has been given to the genetic variability, fundamental parameter for any conservation practices. The objective of this study was to analyze the genetic diversity of Piaractus mesopotamicus stocks used in stocking programs, through the RAPD molecular marker. Sixty broodstocks of two fish farms stations located in the Sapopema (S) and Cambara (C) cities in the Parana State (Brazil) and 30 larvae of the Sapopema offspring (PS) were analyzed. The 10 selected primers yielded 69 fragments of which 62 (89.85%) were polymorphic. Differences (p<0.05) in the frequency of 42 fragments were observed, with four exclusive for the Sapopema stock. The genetic variability results estimated by the percentage of polymorphic fragments (S: 70.15%; PS: 73.13% and C: 77.81%) and for the genetic diversity of Shannon index (S: 0.365; PS: 0.379 and C: 0.468) showed that the genetic variability was maintained in the offspring, due possibly to the good reproductive management. On the other hand, the opposing genetic variability among the two broodstocks indicated a genetic differentiation among them, possibly due to the founder effect. According with the AMOVA, most of the variation is within each stock (62.43%). This result was corroborated with the FST (0.375) values and the effective number of migrants (2.20) that showed a high genetic differentiation and a low gene flow. It was also verified that S and SP were those but similar genetically (genetic identity, IG= 0.851) and that S and C presented less genes in common (IG= 0.786).

Respostas à seleção de características de desempenho em tilápia‑do‑nilo

The objective of this work was to estimate genetic parameters and direct and indirect responses to selection for performance traits in Nile tilapia ( Oreochromis niloticus ), as well as to evaluate the impact of selection on genetic gain. Information about Nile tilapia, under selection in a genetic improvement program, grown in a net‑tank system, from 2008 to 2010, was used. Heritability and genetic correlations for the traits daily weight gain, and, immediately after catching, weight, width, height, and trunk length were estimated, besides the genetic gains obtained by the estimation of genetic tendencies and of the responses to selection for these traits. Heritability estimates were around 30%. The estimates of genetic and rank correlations had high magnitude. The direct genetic gain for daily weight gain was 7.9, 5.18, and 9.43% in 2008, 2009, and 2010, respectively. The genetic gains obtained from the genetic tendencies were 6.36, 6.30, 1.62, 1.65, and 1.51%, respectively, for daily weight gain, and trunk weight, width, height, and length. The increased growth rate through selection positively impacts performance traits in Nile tilapia.

A comparative study of four DNA extraction protocols from adductor muscle in golden mussel (Limnoperna fortunei)

The golden mussel, Limnoperna fortunei, is a mollusk native to Southeast Asia and a highly invasive species in South American countries such as Brazil, Uruguay, and Argentina. In order to better understand the biological behavior of the species and develop alternative control methods, genetic studies involving the optimization of DNA isolation procedures are of utmost importance. The objective of the present study was to develop a simple, reproducible, free of contaminants, and cheap protocol to extract DNA from L. fortunei using the adductor muscle of the mussel as the source. Four DNA extraction protocols were compared: extraction with SDS and proteinase K (P1); extraction with SDS, proteinase K and phenol (P2); TRIzol extraction (P3); and NaCl, SDS and RNase extraction (P4). DNA concentration (ng μL-1) and purity (at 260/280 nm) were measured using a spectrophotometer. DNA purity and amplification were verified by electrophoresis and PCR, respectively. P1 resulted in samples with low DNA concentrations or without any DNA, as revealed by the quantification and purity analysis; P2 had low efficiency, given the absence of DNA in most of the samples subjected to electrophoresis. On the other hand, P3 showed contamination with proteins, as indicated by an absorbance of <1.8 and by the low-quality electrophoresis results. Finally, P4 resulted in well-defined bands, absorbance between 1.8 and 2.0, and successful amplification by PCR. In conclusion, the extraction protocol P4 is a practical, fast, free of contaminants, and efficient method for the isolation of L. fortunei DNA.

Bayesian inference describing statistical models based on the average daily gain of nile tilapia ( Oreochromis niloticus “gift”)

The aim of the current study was to analyze four statistical models using Bayesian inference to describe the average daily gain (g) (ADG) during the genetic selection of the Nile Tilapia (Oreochromis niloticus “GIFT”). The data set had records from 2,615 fish collected from the fourth generation (G4) of the breeding programme in the Floriano Breeding Station of the Universidade Estadual de Maringá, Maringa County, Paraná State, Brazil. In these analyses, we considered an animal model where sex was the fixed effect, linear and quadratic effects of the fish age was covariates in days in conjunction with the additive genetic effects. The models were modified based on the available information from additive genetic effects and common environments of hatchery (c), nursery (w), or none of them. The heritability results were estimated for the models, M2=0.24 and M4=0.23 and high for M1=0.83 and M3=0.79. The criterion of selection in the DIC model was lower for the M1 with -282.59 and higher for M4 with 1754.57. Another criterion of selection was the marginal log density of the Bayer factor which corroborates with the DIC only for the lower value in which M1=585.29. Less computer efforts to achieve convergence was found using the M1 model with 15,000 chains, which was the best model to explain and predict the phenomenon.The aim of the current study was to analyze four statistical models using Bayesian inference to describe the average daily gain (g) (ADG) during the genetic selection of the Nile Tilapia (Oreochromis niloticus “GIFT”). The data set had records from 2,615 fish collected from the fourth generation (G4) of the breeding programme in the Floriano Breeding Station of the Universidade Estadual de Maringa, Maringa County, Parana State, Brazil. In these analyses, we considered an animal model where sex was the fixed effect, linear and quadratic effects of the fish age was covariates in days in conjunction with the additive genetic effects. The models were modified based on the available information from additive genetic effects and common environments of hatchery (c), nursery (w), or none of them. The heritability results were estimated for the models, M2=0.24 and M4=0.23 and high for M1=0.83 and M3=0.79. The criterion of selection in the DIC model was lower for the M1 with -282.59 and higher for M4 with 1754.57. Another criterion of selection was the marginal log density of the Bayer factor which corroborates with the DIC only for the lower value in which M1=585.29. Less computer efforts to achieve convergence was found using the M1 model with 15,000 chains, which was the best model to explain and predict the phenomenon.

Avaliação genética de tilápias‑do‑nilo durante cinco anos de seleção

The objective of this work was to estimate genetic parameters and breeding values for body weight at harvest and daily weight gain of Nile tilapia (Oreochromis niloticus), evaluated in cages for five years. The data set contained records of 6,650 animals, with predicted breeding values of 8,590 animals in the relationship matrix. The number of animals evaluated was 2,196 (33 families) in 2008; 1,721 (58 families) in 2009; and 2,733 (78 families) in 2010. Single and two-trait analyses from the data set were performed using Bayesian inference methodology by the computer program MTGSAM. The obtained heritability estimates were of medium magnitude, as follows: 0.273, for daily weight gain; and 0.282, for body weight at harvest. The participation of common environmental effects in the total variation was of 15% for larvae and 5% for nurseries. The genetic and phenotypic correlations were of 95%, indicating a strong association between the traits. Genetic gain was 3.8% per generation, with accumulated 15% over four generations. There were genetic progress and changes caused by the selection of Nile tilapia in the evaluated growing conditions. The selection for weight gain allows of indirect gains associated to weight.