Origin and evolution of sex chromosomes in neotropical fishes

Abstract

The processes working on sex chromosome differentiation are still not completely understood. However, the accumulation of repetitive DNA sequences has been shown to be one of the first steps in the early stages of such differentiation, in addition to the fact that the absence of recombination between the sex chromosomes favors, by itself, the accumulation of repetitive sequences on these chromosomes. The diversity of sex determining mechanisms in fish, alongside with the absence of heteromorphic sex chromosomes in many species, make this group a useful model to better understanding evolutionary processes of sex chromosomes in vertebrates, considering that fish occupy the basal position in the phylogeny of this group. Therefore, this project aims to analyze the differentiation of simple and multiple sex chromosome systems, exploring the excellent model offered by the Neotropical fishes, through molecular cytogenetic techniques, such as the mapping of repetitive DNA sequences on the chromosomes, microdissection and chromosome painting, allowing the most effective exploitation of the events related to these processes. Some of the proposed studies here are part of the Post Doctoral Project and the Research Scholarship Internship Abroad (Marcelo de Bello Cioffi), recently approved by FAPESP, and related to different sex systems in Erythrinidae species. Such studies will be complemented by the exploration of additional excellent models found in other Neotropical fish groups. The data to be obtained will allow clarifying fundamental aspects of the sex chromosomes evolution among fishes, making also important contributions to understanding the evolutionary processes of the sex chromosome in vertebrates as a whole. (AU)