The gene mapping of Senegalese sole (S. senegalensis)

The Senegalese sole (S. senegalensis) is a common flatfish, distributed over the eastern Atlantic coast from the Northern part of Senegal. Senegalese sole aquaculture has aroused great interest in the marine aquaculture in Spain and Portugal because of its relatively rapid growth rate, but it presents limits due to the poor reproduction of captive breeders in many facilities. In fact gonad development during sexual maturation results in major growth reduction, and increased susceptibility to diseases (Felip et al., 2006). Senegalese sole has 42 chromosomes and an XX/XY chromosome system for sex determination, while related species show the ZZ/ZW system. In S. senegalensis, these problems are aggravated because of the lack of knowledge concerning sex. This study fits into a detailed project of Senegalese sole knowledge, promoted by University of Cádiz, providing new information about the karyotype characterization, the chromosome structure of certain genes involved in sex determination and sexual differentiation processes, which may be relevant for improving the commercial production of this species. This piece of information not only helps to understand the development and evolutionary mechanism in vertebrates, but will also contribute to improving the production of target species for aquaculture. For this purpose, several bacterial artificial chromosome (BAC) clones that contain candidate genes involved in such processes (Vitellogenin, Otospiralin, R-spondin-1, Steroidogenic Factor1 and Tetkin-2) were analyzed and compared, where possible, with the same genes in other species. In this study it was possible to describe a part of those four genes, using 3’ RACE method. The BAC-FISH results showed the position of different genes in different chromosome, to improve the knowledge of Senegalese sole karyotype. In particular, the localization of steroidogenic factor 1 (SF1) in the chromosome 1 that is involved in the sex determination.