A conserved karyotype of Sternopygus macrurus (Sternopygidae, Gymnotiformes) in the Amazon region: differences from other hydrographic basins suggest cryptic speciation.
We studied the karyotypes of 35 Sternopygus macrurus fishes of four localities from rivers of the Eastern Amazon basin. In these four places the karyotypes have 2n=46 chromosomes, NF=92, where 30 are metacentric (M) and 16 submetacentric (SM). The constitutive heterochromatin (CH) is found in the centromeric region of most chromosomes and in the pericentromeric region of pairs 5, 17 and 19. Pair 1 has a large and not common heterochromatic block in the short arm, useful as a marker for this species if not found in other Sternopygus taxa. The NOR is located in the distal region of the short arm of pair 1, showing a size heteromorphism in some specimens. The CMA(3) and DAPI fluorochrome bandings and the fluorescent in situ hybridization (FISH), using pantelomeric human probes techniques are described for the first time for this species. DAPI has banding coincident with the C-banded regions, which suggests that the CH is AT base-pair-rich. CMA(3) banding is coincident with the NOR, meaning that this region is GC base-pair-rich. The FISH showed that the probes hybridized only with the telomeric regions, without any sign of interstitial telomeric regions. The karyotype of the samples from different places in the Amazon basin is quite conserved, probably because of the gene flow among the populations. The karyotype differences among the Sternopygus macrurus from the Amazon basin and the São Francisco and Paraná rivers suggest that these taxa may be different species.
dos Santos Silva
Danillo
D
Bolsista CAPES de Mestrado em Genética e Biologia Molecular, Brazil.
Milhomem
Susana Suely Rodrigues
SS
de Souza
Augusto Cezar Paes
AC
Pieczarka
Julio Cesar
JC
Nagamachi
Cleusa Yoshiko
CY
D000818:Animals; D002869:Chromosome Aberrations; D002871:Chromosome Banding; D023702:Gymnotiformes / Q000145:classification / Q000235:genetics*; D006570:Heterochromatin; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping
D006570:Heterochromatin