| Resumo: |
Prochilodus lineatus is a species of high incidence in the upper Paraná River basin, involving mainly the Grande, Pardo and Mogi-Guaçu Rivers. Cytogenetically, this species has a diploid number of 54 meta/submetacentric chromosomes and presents an interesting system of B microchromosomes, which can occur interindividual variation from zero up to nine supernumeraries, also it presents polymorphism and can be found in different morphotypes. P. lineatus can be considered a model species of neotropical fish, commonly used for studies concerning the origin, behavior and evolution of B chromosomes, due to ease of capture, handling, high frequency of supernumerary and polymorphism. Currently, there are only speculations about its function, origin and inheritance, which make the analysis of the DNA structure of this chromosomal type, as well as the study of the inheritance pattern, of the utmost importance. Faced with this, the present work aimed to study the origin, maintenance and inheritance of the B chromosomes variants found in P. lineatus from Mogi-Guaçu River, from DNA composition analysis, frequency in natural population and transmission pattern of these genomic elements. The results obtained from the inheritance analysis of these supernumerary showed a dynamism between supernumerary variants to prevail in the host genome through the transmission pattern (kB), in which the B-metacentric morphotype presented kB above Mendelian ratio, indicating a possible accumulation mechanism (drive), while the B-acro and B-submetacentric variants presented kB below Mendelian ratio, indicating that they were in extinction stage. When performing the chromosome painting technique, using B-specific probes obtained from each microdissected morphotypes, it was observed a homology between the B chromosome variants, indicating a common ancient variant origin. However, only the B-submetacentric chromosome probe (Bsm) showed ... |
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