RESUMO Objetivou-se caracterizar a variabilidade genética de cinco grupos de Pseudoplatystoma reticulatum Mato Grosso I (MT-I), Mato Grosso II (MT-II), Mato Grosso III (MT-III), Mato Grosso do Sul I (MS-I) e Mato Grosso do Sul II (MS-II) pertencentes a um núcleo de melhoramento genético. Para determinação das medidas de frequências alélicas, heterozigosidade observada (HO), coeficientes de endogamia (FIS), teste do equilíbrio de Hardy-Weinberg (HW-p) e diferenciação genética foram selecionados oito loci polimórficos de microssatélites (Pcor01, Pcor05, Pcor08, Pcor10,Ppu01, Ppu04, Ppu09, pu10) nos quais observaram-se um total de 62 alelos nos indivíduos (n=211). A População MS-I apresentou o maior (Pcor08 alelo 83:0,5000) e menor (Pcor10 alelo 50: 0,1667) valor de frequência alélica média. Maiores (HO= 0,782; 0,782) e menores (FIS= 0,034; 0,061) foram verificados nos grupos MS-I e MT-III respectivamente e o HW-p exibiu que os cinco grupos apresentaram desvios para a maioria dos loci analisados. Por último, diferenciação genética apontou a formação de dois grandes grupos genéticos, um conformado pelos grupos provenientes do Mato grosso e outro pelos grupos do Mato grosso do Sul. Essas medidas podem auxiliar na seleção do programa de melhoramento, permitindo a manutenção da variabilidade genética.

ABSTRACT The aim of this study was to characterise genetic variability in five groups of Pseudoplatystoma reticulatum: Mato Grosso I (MT-I), Mato Grosso II (MT-II), Mato Grosso III (MT-III), Mato Grosso do Sul I (MS-I) and Mato Grosso do Sul II (MS-II), taken from a centre for genetic improvement. In order to determine the allelic frequency, observed heterozygosity (HO), inbreeding coefficients (FIS), Hardy-Weinberg equilibrium (HW-p) and genetic differentiation, eight polymorphic microsatellite loci (Pcor01, Pcor05, Pcor08, Pcor10, Ppu01, Ppu04, Ppu09 and Ppu10) were selected, in which a total of 62 alleles were observed in the individuals (n = 211). The MS-I population had the highest (Pcor08 allele 83: 0.5000) and lowest (Pcor10 allele 50: 0.1667) mean values for allele frequency. Higher (HO = 0.782; 0.782) and lower (FIS = 0.034; 0.061) values were found in groups MS-I and MT-III respectively. The HW-p showed that the five groups presented deviations for most of the loci under analysis. Finally, genetic differentiation pointed to the formation of two large genetic groups, one formed by the groups from Mato Grosso and the other by the groups from Mato Grosso do Sul. These measurements can help selection in a breeding program and maintain genetic variability.

ABSTRACT: This study evaluated pre-slaughter stress and its influence on the stress indicators, quality characteristics and sensory characteristics of Nile tilapia fillets. To this end, two experiments were conducted: (1) two transportation times (60 and 240 min), with a density of 200 kg m−3, were compared to control treatment fish (in which the fish were removed from the net cage and immediately euthanized); and (2) two transportation densities (100 and 400 kg m−3), transported for 180 min, compared with control treatment fish. In experiment 1, the transportation time of 60 min resulted in higher levels of serum cortisol and plasma glucose compared to the transportation time of 240 min and the control. Fish fillets transported for 240 min had higher water-holding capacity, less water loss by pressure and higher levels of juiciness compared to fish transported for 60 min. Color, pH and water loss during cooking were not affected by transportation time. In experiment 2, transportation densities of 100 and 400 kg m−3 did not significantly affect the stress indicators nor the instrumental quality parameters of the fillets, but fish transported at 400 kg m−3 showed better visual acceptance by panellists.