Karyotypic analysis in two species of fishes of the family Curima-tidae: AgNO₃, CMA₃ and FISH with 18S probe

Abstract

Two species of fishes of the family Curimatidae, Cyphocharax modestus and Steindachnerina insculpta, collected in Tibagi river basin (Paraná, Brazil), were cytogenetically analysed and showed a diploid number of 54 chromosomes m-sm. An AgNOR was observed at the terminal position of chromosome pair 2 for Cyphocharax modestus and in pair 7 for Steindachnerina insculpta. Treatment with fluorochrome CMA₃ and fluorescence in situ hybridization (FISH) with an 18S rDNA probe showed staining corresponding to the AgNOR pair for both of the species studied. One individual of C. modestus, collected in the Taquari stream, had only one AgNOR chromosome, where silver nitrate impregnation stained a large portion in chromosome long arm, corresponding to the secondary constriction. An identical result was obtained with CMA₃ staining. The FISH technique showed that one of the sites was large and corresponded to NOR and CMA₃ staining and that the other was very small, indicating the possible occurrence of unequal crossing-over between homologous chromosomes.

Key words:

• AgNOR
• CMA3 staining
• Curimatidae
• FISH