First Chromosome Data about the silverside Atherinella brasiliensis (Atheriniformes, Pisces) from the South coast of Brazil. Conventional, C- NOR and CMA₃ bandings and FISH studies

Abstract

Cytogenetic studies of A. brasiliensis from the south coast of Brazil were made with specimens of two populations: Baia de Paranaguá and Lagoa da Conceição. All the individuals analyzed presented a diploid number of 48 chromosomes with a standard karyotype constituted by 4M + 10SM + 14ST + 20A (FN=76). There have been found five different cytotypes (A to E) in the specimens of the Baia de Paranaguá/PR, while in the Lagoa da Conceição/SC just two (standard and F). These cytotypes are characterized by changes in the number of M and SM chromosomes and these differences could be due to pericentric inversions. The C-banding regions were evidenced in pericentromeric and telomeric regions also staining positively the secondary constrictions. NORs detected by AgNO₃ and CMA₃ staining are located at the short arms of acrocentric chromosomes (19th pair) and these techniques evidence a size heteromorphism between the homologue chromosomes. The heteromorphism of the NOR bearing chromosome was not detect by FISH technique with rDNA 18S probe and these results allow to suggest that this heteromorphism could be of functional origin.

Key words:

• Atherinella brasiliensis
• Fish Cytogenetics
• Chromosome Polymorphisms
• Ag-NOR
• CMA₃
• FISH