Abstract
The Iguazu river is a tributary of the left margin of the Paraná river, isolated from this basin about 22 million years ago with the appearance of the Iguazu Falls. The Iguazu river is characterized by high endemism due to two factors: its rugged topography and the old isolation caused by formation of the Iguazu Falls. This study analyzed cytogenetically a population of Glanidium ribeiroi collected in a region at the final stretch of this basin, by Giemsa staining, C-banding, impregnation by silver nitrate, and FISH with probes of 5S rDNA, 18S rDNA, telomeric sequence [TTAGGG]n, and [GATA]n repeats. The diploid number was equal to 58 chromosomes. The heterochromatin was present in the terminal region of almost all chromosomes. The Ag-NORs were simple and presented interstitially on the short arm of the submetacentric pair 14, which was confirmed by FISH with 18S rDNA probe. The 5S rDNA-FISH marked only the submetacentric pair 16 on the long arm in interstitial position. The FISH with [TTAGGG]n probe presented all telomeres labeled as expected, with an absence of Interstitial Telomeric Sequence (ITS). The repetitive [GATA]n sequence was dispersed throughout the genome, with preferential location in the terminal region of all chromosomes. The data obtained are discussed herein with other species of Auchenipteridae, and other previously analyzed populations of G. ribeiroi from the Iguazu river, verifying differences among these populations, which should be mainly related to the rugged topography of this basin.
Highlights
Among the Siluriforms, Auchenipteridae comprises a group of endemic fish to the Neotropical region
G. ribeiroi was recently considered endemic to the Iguazu river basin (Ferraris Junior, 2007), according to Akama and Sarmento-Soares (2007), this species can be found in other rivers in the Paraná basin, in the states of Paraná and São Paulo
The hybridization with the repetitive [GATA]n sequence shows that this marker is dispersed throughout the genome, with a preferential location in the terminal region of the chromosomes; a lesser amount was observed in the interstitial chromosomal regions
Summary
Among the Siluriforms, Auchenipteridae comprises a group of endemic fish to the Neotropical region. This family comprises about 90 species distributed in 20 genera (Ferraris Junior, 2007), of which 74 have already been registered in Brazil (Akama and Sarmento-Soares, 2007). According to Ferraris Junior (2003), Auchenipteridae is divided into two subfamilies, Centromochlinae and Auchenipterinae. The subfamily Centromochlinae has 31 valid species Seven of these species belong to the genus Glanidium (Ferraris Junior, 2007). G. ribeiroi was recently considered endemic to the Iguazu river basin (Ferraris Junior, 2007), according to Akama and Sarmento-Soares (2007), this species can be found in other rivers in the Paraná basin, in the states of Paraná and São Paulo
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