Cytogenetics of Imparfinis schubarti (Siluriformes: Heptapteridae) from the Piumhi drainage, a diverted river in Minas Gerais State, Brazil

Abstract

Specimens of Imparfinis schubarti (Gomes, 1956) collected in the Piumhi river drainage, state of Minas Gerais, Brazil, were studied cytogenetically. The river was diverted from the Rio Grande Basin into the São Francisco basin in the early 1960s. All individuals presented 2n = 58 chromosomes, including 18 metacentric, 34 submetacentric and six subtelocentric chromosomes. A secondary constriction was observed in the interstitial region of the long arm of the largest chromosome pair, coinciding with the NOR. A single conspicuous heterochromatic block located in the largest pair of metacentric chromosomes was observed, adjacent to the secondary constriction. A detectable 18S rDNA probe hybridization region occurs in only one chromosome pair and is synthenic with the marking obtained with 5S rDNA probe. These results fit the cytogenetic pattern previously described for the genus Imparfinis Eigenmann & Norris, 1900

Isolation and characterization of 5S rDNA sequences in catfishes genome (Heptapteridae and Pseudopimelodidae): perspectives for rDNA studies in fish by C0t method

“…In contrast, Kantek et al (2009) observed this site only in a big submetacentric chromosome pair of the constriction that also showed synteny with the 18S rDNA site in I. schubarti from Pihumi River/MG/ Brazil. However, the two populations of I. schubarti, in this study, showed the 5S rDNA site on a small metacentric chromosome (pair 10), which does not show synteny with the 18S rDNA site, as was observed with the double FISH technique.…”

“…However, there is variation regarding the chromosome type and presence of such sequences either on the short or long arm, even within the same species (Kantek et al 2009;Garcia and AlmeidaToledo 2010a, b;Martinez et al 2011). The Heptapteridae family also shows variation in chromosome number bearing this site, and only one pair of chromosomes (Kantek et al 2009;Garcia and Almeida-Toledo 2010a;Martinez et al 2011) or two pairs of chromosome carriers are found (Garcia and Almeida-Toledo 2010a, b;Ferreira et al 2014).…”

“…Studies performed by Kantek et al (2009) show the occurrence of 5S rDNA in Imparfinis schubarti (Gomes 1956) syntenic with 18S rDNA sites in the interstitial region of the largest chromosome pair. Imparfinis mirini Haseman 1911 and Imparfinis minutus (Lutken 1874) analyzed by Ferreira et al (2014) also showed the same synteny, besides presenting another small metacentric pair, bearer of a single 5S rDNA site in the region near the centromere.…”

Cytogenetic characterization of species of the family Heptapteridae (Teleostei: Siluriformes) from the Cuiabá and Ivaí River Basins, Brazil

“…schubarti (Kantek et al, 2009), were similar in terms of the Ag-NORs. The NORs observed on the long arm of different types of chromosome in this genus can be explained by rearrangements, such as inversions, deletions, and duplications (Borba et al, 2011).…”

“…The values of 2n = 58 chromosomes and NF = 116, which were found in the present study, are the most common in the genus, being also observed in I. mirini (Vissotto et al, 1997), I. piperatus (Vissotto et al, 2001), I. aff. schubarti (Stolf et al, 2004), and I. schubarti (Kantek et al, 2009). Differences in karyotype formula and 2n have been found between different species and populations of Imparfinis; however, the high frequency of species with 2n = 58 chromosomes, which is considered not only ancestral for the Heptapteridae but also for the Siluriformes as a whole, indicate that non-Robertsonian chromosomal rearrangements were the most frequent rearrangements made during the karyotypic evolution of the genus.…”