title: Karyotype and chromosomal characteristics of Ag-NOR sites and 5S rDNA in European smelt, Osmerus eperlanus.
abstract: Karyotype and cytogenetic characteristics of European smelt Osmerus eperlanus were investigated using different staining techniques (sequential Ag-, CMA3 and DAPI banding) and PRINS to detect 5S rDNA and telomeric sites. The diploid chromosome number was invariably 2n = 56 and karyotype composed of 5 pairs of metacentrics, 9 pairs of subtelocentrics and 14 pairs of subtelo- to acrocentrics. The DAPI-positive heterochromatic regions were found in centromeric positions on bi-armed chromosomes and few acrocentrics. Additionally, some interstitial DAPI-positive bands were identified on three pairs of submetacentric chromosomes. The nucleolar organizer regions (NORs) were detected in the short (p) arms of the largest metacentric pair of chromosomes No. 1. Sequential banding (Giemsa-, AgNO(3) and CMA(3) stainings) revealed NOR sites corresponding to achromatic regions but not associated with CMA(3)-positive blocks of heterochromatin located on either side of NORs. Individuals from the analyzed population had this conspicuous pair of chromosomes always in heterozygous combination. A complex inversion system was hypothesized to be involved in the origin of the observed variation but analysis with telomeric PRINS and PNA-FISH did not reveal any Interstitial Telomeric Sites (ITS). Hybridization signals were confined exclusively to terminal chromosomal regions. The 5S ribosomal sites as revealed by PRINS were found to be invariably located in the short (p) arms of four pairs of subtelocentric chromosomes. Cytotaxonomic comparisons of the present results with the voluminous available cytogenetic data-set from salmoniform and esociformes fishes appear to support the recent view, based on robust molecular-based phylogeny, that salmoniform and osmeriform fishes are not as closely related as previously assumed.
authors.affiliation: Department of Ichthyology, University of Warmia and Mazury in Olsztyn, ul. Oczapowskiego 5, 10-718 Olsztyn-Kortowo, Poland. con@uwm.edu.pl
authors.forename: K
authors.initials: K
authors.lastname: Ocalewicz
authors.forename: P
authors.initials: P
authors.lastname: Hliwa
authors.forename: J
authors.initials: J
authors.lastname: Krol
authors.forename: M
authors.initials: M
authors.lastname: Rábová
authors.forename: R
authors.initials: R
authors.lastname: Stabinski
authors.forename: P
authors.initials: P
authors.lastname: Ráb
mesh_terms: D000818:Animals; D002871:Chromosome Banding; D002875:Chromosomes / Q000502:physiology*; D004275:DNA, Ribosomal / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D009697:Nucleolus Organizer Region; D036441:Osmeriformes / Q000235:genetics*; D016622:Silver Staining
chemical_list: D004275:DNA, Ribosomal