Description of a new karyotypic formula and chromosome B variant in Callichthys callichthys (Siluriformes, Callichthyidae)

• Grant number: 25/01598-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: May 01, 2025
• End date: December 31, 2025
• Field of knowledge: Biological Sciences - Genetics - Animal Genetics
• Principal Investigator: Fábio Porto-Foresti
• Grantee: Maria Eduarda Rodrigues Melo
• Host Institution: Faculdade de Ciências (FC). Universidade Estadual Paulista (UNESP). Campus de Bauru. Bauru , SP, Brazil

Abstract

Fish cytogenetics has revealed the remarkable diversity and complexity of Neotropical ichthyofauna. Among the most studied components are B chromosomes, which are extranumerary fragments of the main genome that evolve independently. These chromosomes are observed in various fish species, including Callichthys callichthys from the family Callichthyidae, a species with significant chromosomal variation that is widely used as a model in evolutionary and cytogenetic studies. This study aims to describe the karyotypic diversity of Callichthys callichthys using cytogenetic markers, analyzing specimens from two previously unstudied populations: one from the Alambari River in Bauru, São Paulo, and another from the Mogi-Guaçu River in Pirassununga, São Paulo. Furthermore, the study will investigate the frequency and characteristics of potential B chromosome variants in these populations. The application of cytogenetic techniques will enable a detailed analysis of the chromosomes and their evolutionary traits. These analyses will contribute to a better understanding of chromosomal evolution, including speciation processes and the genetic diversification of this species.