Conventional Cytogenetic Approaches—Useful and Indispensable Tools in Discovering Fish Biodiversity

Abstract

Fishes exhibit the greatest biodiversity among extant vertebrates. In fact, about 34,000 fish species are currently estimated, of which ~ 25% are living in Neotropical freshwaters. Currently, several leading-edge studies using molecular biology procedures have largely contributed to the investigation of the fish genomic architecture at the chromosomal level. In this review, we intend to demonstrate that conventional cytogenetics is also a powerful procedure to identify and clarify both individual and inter- or intrapopulational fish characteristics and to unveil their biodiversity. Intra- or interpopulational chromosomal characteristics, revealing dramatic processes of evolution and cryptic divergence and even speciation, as well as unusual cases of interspecific hybridization, clonal reproduction, and sex chromosome differentiation, were, and still are, unmistakably discovered among fishes by using conventional, i.e., non-molecular cytogenetic procedures. In this review, we aim to demonstrate that conventional cytogenetics constitutes a powerful and indispensable tool in characterizing the hidden biodiversity of the ichthyofauna. We focus on some key examples that clearly illustrate the importance and the efficiency of this approach.