Os peixes híbridos e sua fragilidade reprodutiva

The hybrids originate from matings between population groups of distinct genetic basis, for one or more inherited trait, whose variability may contribute to the occurrence of reproductive types and ecological interactions of more different habitats. Therefore, understanding the mechanisms of hybridization becomes an important prerequisite for the identification of specific genetic changes, which are responsible for the characterization of the species and for the reducing of the fitness of these hybrids. It has been show in offspring from crosses of genetically divergent populations unfavorable interactions of parental genomes of individuals provided by introgressão (transfer of genetic material from one species to another via hybridisation), documented in animals and especially in a wide variety of plants. In fish such combinations result is sometimes a favorable productive expression, as shown in tilapia, with the achievement of only male individuals, favoring management and growth, while in others not so much, sach as gynogenetic P. mesopotamicus individuals, which leave no progeny F2 hybrid. When the diploid progenitor species have identical numbers and the chromosomes are inherited equally, these hybrids are usually fertile offspring. In most of these hybrid types occurs sexual reproduction, with its diversity promoted through meiotic recombination, while in a minority, unisexual, occurs asexual reproduction, without the occurrence of any modification by recombination on the offspring inheritance. This hybridization, leading to the production of the recombinant previously not subjected to selection, therefore, consists, on average, of individuals less adapted than their parents. Thus, hybridization, due to its complexity, becomes a crucial factor to understand heterosis and introgression systems, with respect to the parent species, as well as the development of hybrids over time. Os híbridos se originam a partir de acasalamentos entre grupos populacionais de base genética distinta em uma, ou mais, caraterística hereditária, cuja variabilidade pode contribuir para a ocorrência dos tipos reprodutivos e interação ecológica dos mais diferentes habitats. Por isso, o entendimento dos mecanismos da hibridização torna-se um pré-requisito importante na identificação de mudanças genéticas específicas responsáveis pela caracterização de espécie e redução do fitness desses híbridos. Nesses descendentes híbridos, cujas populações cruzadas são geneticamente divergen