Cytogenetic Trends in Two Families of the Neotropical Catfishes: Heptapteridae and Pseudopimelodidae (Siluriformes).

Several neotropical Siluriformes groups suffered important taxonomic revisions based on the evaluation of morphological and molecular characteristics that allow the construction of new phylogenetic hypothesis. In the present study were cytogenetically analyzed six species belonging to Heptapteridae (Cetopsorhamdia iheringi, Phenacorhamdia tenebrosa, Rhamdella eriarcha, Pimelodella meeki, Pimelodella australis, Heptapterus mustelinus) and two to Pseudopimelodidae families (Microglanis cottoides and Microglanis cibelae) by means of differential staining techniques to describe more precisely cytogenetic similarities and differences. The diploid number of R.

Cytogenetic studies in the redtail catfish, (Bloch & Schneider, 1801) (Siluriformes, Pimelodidae) a giant fish from Amazon basin.

The objective of this study was to cytogenetically analyze comparing the findings with other data to infer relationships among Pimelodidae species. The results revealed a diploid number of 2n = 56 and the karyotype composed of 16 metacentric, 20 submetacentric, 6 subtelocentric and 14 acrocentric chromosomes (FN = 98). The Ag-NORs, 18S rDNA and CMA signals were coincident in location occupying the short arm of an acrocentric chromosome pair (23), in a secondary constriction.

Cytogenetic characterization of (Bloch, 1794) from the Ctalamochita River (Córdoba, Argentina): first evidence for southernmost populations of this species complex and comments on its biogeography.

(Bloch, 1794), a predatory freshwater fish with a wide distribution throughout South America, represents a species complex with seven well characterized karyomorphs at the cytogenetic level. Although this species has been extensively studied in several Brazilian basins, data are still scarce for hydrographic systems from other South American countries. This study aims to characterize cytogenetically the populations from the Argentinean Central Region, close to the southernmost distribution of this species complex.

The importance of pericentric inversions in the karyotypic diversification of the species Loricariichthys anus and Loricariichthys platymetopon.

Catfishes of the genus Loricariichthys are widely distributed in the Platina Basin. Considering that the cytogenetic knowledge of Loricariichythys is underestimated, this study assessed Loricariichthys anus and Loricariichthys platymetopon through different chromosome bandings, to define the mechanisms determining the variability in these species. Cytogenetic analyses evidenced a high degree of similarity in relation to the 2n (54 chromosomes), as well as to the distribution of heterochromatin.

Cytogenetics of the Porthole Shovelnose Catfish, Hemisorubim platyrhynchos (Valenciennes, 1840) (Siluriformes, Pimelodidae), a widespread species in South American rivers.

Hemisorubim platyrhynchos is a medium- to large-sized pimelodid catfish distributed along several river basins of the Neotropical Region, noteworthy for representing an important fishery source. In this work, Hemisorubim platyrhynchos from three isolated populations were cytogenetically analyzed. The karyotype shows a diploid number of 2n=56 chromosomes comprising 22m, 16sm, 10st, 8a (FN=104).

Analyses of the structure of NORs in two species of South American Sorubiminae fishes (Siluriformes) by means of several cytogenetic techniques.

Several cytogenetic techniques (AgNOR, C- G- and RE bandings, DAPI, CMA3 and FISH) were applied in order to analyze the structure and variability of NORs in the fish species Steindachneridion melanodermatum and S. scripta. Ag-NORs were observed on the short arm of the first acrocentric chromosome pair, coincidentally with a strong C-positive band on a large secondary constriction.

First chromosome data on Steindachneridion scripta (Pisces, Siluriformes, Pimelodidae) from Brazilian rivers: Giemsa, CBG, G-, and RE banding.

A cytogenetic study was performed on the large pimelodid species Steindachneridion scripta (Siluriformes, Sorubiminae) from the Paraná River basin (Brazil). Chromosome preparations were obtained avoiding sacrifice of the specimens, by means of lymphocyte culture, and several staining and chromosome banding techniques were applied. The karyotype consisted of 56 chromosomes, 24 metacentrics, 20 submetacentrics, 4 subtelocentrics, and 8 acrocentrics (fundamental number = 104).

Karyotypic characterization and NOR analysis by different banding techniques of Rhamdia quelen (Pisces, Pimelodidae) from the first plateau of the Iguaçu River (Brazil).

A population of R. quelen from the first plateau of the Iguaçu River (Paraná State, Brazil) was analyzed cytogenetically. A diploid set of 58 chromosomes was constituted by 32 M, 16 SM, 6 ST and 4 A (FN=116).