Animal Cytogenetics and Comparative Mapping

Chromosomal characteristics of ribosomal DNA in two extant species of North American mudminnows Umbra pygmaea and U. limi (Euteleostei: Umbridae)
P. Ráb^a, E.J. Crossman^b, K.M. Reed^c, M. Rábová<sup>a

a</sup>Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Libchov(CzechRepublic);
^bRoyal Ontario Museum, Centre for Biodiversity and Conservation Biology, Toronto, Ont. (Canada);
^cDepartment of Veterinary PathoBiology, College of Veterinary Medicine, University of Minnesota, St. Paul MN (USA)

Address of Corresponding Author

Cytogenet Genome Res 2002;98:194-198 (DOI: 10.1159/000069800)

  Abstract.

The locations and chromosomal characteristics of ribosomal DNA (rDNA) sites in the karyotypes of two extant North American species of mudminnows, Umbra pygmaea and U. limi (2n = 22, NF = 44), were analyzed sequentially by conventional Giemsa staining, Ag staining, CMA₃ fluorescence and fluorescence in situ hybridization (FISH). The nucleolar organizer regions (NORs) were located in the fourth chromosomal pair in both species (pericentromeric region in U. pygmaea and subtelomeric in U. limi). These sites were strongly CMA₃-positive suggesting that the rDNA sites in these species are associated with GC-rich DNA. FISH with a rDNA probe gave consistently positive signals in the same regions detected by Ag-staining and CMA₃-fluorescence. However, both species also had additional CMA₃-positive/Ag-negative heterochromatic blocks at pericentrometric regions of several chromosomal pairs (three in U. pygmaea and five in U. limi). FISH revealed additional rDNA clusters in both species. It is hypothesized that a paracentric inversion of the chromosome arm carrying the NORs might be one of the rearrangements differentiating the karyotypes of two North American species. The presence of additional rDNA sites is indicative of more complex rearrangements. The pericentromeric NOR phenotype of Umbra pygmaea is similar to that seen in U. krameri and in the distantly related genus Esox.   

Copyright © 2002 S. Karger AG, Basel

  Author Contacts

Request reprints from P. R b, Laboratory of Fish Genetics
Institute of Animal Physiology and Genetics
Czech Academy of Sciences, 277 21 Libchov (Czech Republic)
telephone: 420 315 639511; fax: 420 315 697186
e-mail: rab@iapg.cas.cz

  Article Information

Supported by Grant No. 204/93/0432 by Grant Agency of the Czech Republic (P.R.), Grant A-1705 National Science and Engineering Research Council (E.J.C.), NRI Competitive Grants Program/USDA (93-37205-9171) (K.M.R) and Grants AS CR K6005114 and S5045111 (M.R., P.R.).

Received 4 January 2003;
manuscript accepted 7 January 2003.
Number of Print Pages : 5
Number of Figures : 4, Number of Tables : 0, Number of References : 19