Cytogenetic Analysis of A- and B-Chromosomes of Iheringichthys labrosus (Pisces, Pimelodidae) from the Tibagi River, Paraná, Brazil

Abstract

Eleven specimens of Iheringichthys labrosus, collected from the Tibagi River (Londrina, Paraná, Brazil) were analyzed cytogenetically, and were found to have a diploid chromosome number of 56, with a karyotype of 32Mϩ8SMϩ6STϩ10A and fundamental number (FN) of 102. In addition, supernumerary chromosomes or Bs varying from 0 to 3 were detected. C-banding revealed heterochromatin distributed mainly in telomeric regions, with a pair strongly stained on both telomeres. The B-chromosomes were totally heterochromatic. The restriction endonuclease (RE) AluI produced a band pattern almost similar to C-banding, and B-chromosomes showed no target sequences for RE.

Cytogenetic analysis of the 18S, 5S rDNA and B chromosome of Iheringichthys labrosus (Lütken, 1874) (Siluriformes, Pimelodidae)

“…Only some populations of I. labrosus have been studied from a cytogenetic perspective, demonstrating a diploid number of 56 chromosomes, with the presence of up to three supernumerary chromosomes or Bs (Vissotto et al, 1999;Carvalho et al, 2004;Carvalho and Dias, 2005a).…”

“…Only five species among those of the family Pimelodidae have such chromosomes: Bergiaria westermanni (Lütken, 1874) (Dias and Foresti, 1993), Iheringichthys labrosus (Vissotto et al, 1999;Carvalho et al, 2004;Carvalho and Dias, 2005a), Pimelodus ortmanni Haseman, 1911 and Pimelodus sp. NUP690, NUP1664, NUP1786, NUP1826 (NUP refers to the ichthyological collection of NUPELIA, Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura of Universidade Estadual de Maringá, PR, Brazil) (Borin and Martins-Santos, 2004) and Megalonema platanum (Günther, 1880) (Carvalho, 2008).…”

Cytogenetics analyses among populations of the fish Iheringichtys labrosus (Kröyer, 1874) (Siluriformes, Pimelodidae). Karyotype analysis, C- banding and AgRONs distribution

“…Previous cytogenetic studies in I. labrosus report the same features, i.e., the diploid number of 56 chromosomes, the absence of sex chromosomes, and the presence of simple AgNORs, coincident with the heterochromatic segments located in the terminal position in the long arm of a st/a pair (Vissotto et al, 1999;Carvalho et al, 2004;Carvalho and Dias, 2005a). A remarkable feature evidenced in this work is that all the seven populations studied along the Paraná river show the same chromosome number and karyotype formula (42m/sm+14st/a).…”

“…The presence of AgNORs in telomeric position on the long arm of chromosome st-a appears as a cytogenetic feature shared by closely related genera as Bergiaria Eigenmann &Norris, 1901 (Dias and, Iheringhichthys Eigenmann & Norris, 1900 (Carvalho et al, 2004;Carvalho and Dias, 2005a), Parapimelodus and Pimelodus Lacépède, 1803 (Garcia and Moreira-Filho, 2005;Swarça et al, 2001). One exception is the population from the Guaraúna River (Paraná, Brazil), where the NOR is found on the short arm of a sm pair (Ribeiro et al, 2008).…”

“…Chromosomal studies performed in different Brazilian populations of this species showed karyotyopes composed of 2n=56 and NF usually reported being greater than 100, AgNORs present in one chromosomal pair and conspicuous C bands predominantly located in the telomeric regions (These data are summarised in Table 1). Some populations showed B chromosomes (Vissotto et al, 1999;Carvalho et al, 2004;Carvalho and Dias, 2005a). Papers on Neotropical fish cytogenetics show differences in karyotypes and formulas into the same species that are frequently attributed to "polymorphisms" however, in many cases the results could be due to technical problems and/ or to the subjectivity of the researcher.…”