Zoologischer Anzeiger 253 (2014) 316–320 Contents lists available at ScienceDirect Zoologischer Anzeiger jou rn al h om epage : w ww.elsevier.com/locate/jcz Chromosomal evolution in naked catfishes (Bagridae, Siluriformes): A comparative chromosome mapping study Weerayuth Supiwong a,c , Thomas Liehr a , Marcelo B. Cioffi b , Arunrat Chaveerach c,∗ , Nadezda Kosyakova a , Krit Pinthong d , Tawatchai Tanee e , Alongklod Tanomtong c a Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Kollegiengasse 10, Jena D-07743, Germany b Departamento de Genética e Evoluc ¸ ão, Universidade Federal de São Carlos, São Carlos, SP, Brazil c Department of Biology, Faculty of Science, Khon Kaen University, 123 Mitraphap Highway, Khon Kaen 40002, Muang District, Thailand d Faculty of Science and Technology, Surindra Rajabhat University, 186 Moo 1, Surin 32000, Maung District, Thailand e Faculty of Environment and Resource Studies, Mahasarakham University, Muang 44000, Mahasarakham, Thailand a r t i c l e i n f o Article history: Received 19 November 2013 Received in revised form 24 February 2014 Accepted 25 February 2014 Available online 4 March 2014 Corresponding Editor: Dr. Alexander Kupfer. Keywords: FISH Microsatellites Rex element Transposable elements a b s t r a c t We analyzed the distribution of repetitive DNA sequences on the chromosomes of nine species of the Bagridae from Thailand, i.e., Hemibagrus filamentus; H. nemurus; H. wyckii; H. wyckioides; Mystus atrifascia- tus; M. multiradiatus; M. mysticetus; M. bocourti and Pseudomystus siamensis. Two classes of microsatellites and one transposable element (TE) were mapped by fluorescence in situ hybridization. The distribution of the repetitive sequences was comparatively analyzed in view to investigate their contribution in the chromosomal evolution of this fish group. In all species the microsatellites (CA) 15 and (GA) 15 are abun- dantly distributed in all chromosomes, usually in the telomeric regions. The retrotransposable element Rex 1 is widely distributed over the whole genome including heterochromatin and euchromatin, but with an unexpected accumulation in one chromosome pair in some species. In fact, some species–specific patterns could be observed considering both microsatellites and TE distribution. The results demon- strated that the compartmentalization of repeated elements is not simply restricted to heterochromatic regions, as it has been postulated in the first concepts of the genomic organization of repetitive ele- ments in genomes. Moreover, the organization of these repeats seems to reflect their intense and specific evolutionary pathway, providing new insights about the chromosomal evolution in the Bagridae. © 2014 Elsevier GmbH. All rights reserved. 1. Introduction Bagrid fishes (order Siluriformes) have a wide geographic distribution throughout Africa and Asia, being also found in sev- eral hydrographic basins of Thailand (Nelson, 2006). Six genera (Bagrichthys Bleeker, 1857, Batasio Blyth, 1860, Hemibagrus Bleeker, 1862, Mystus Scopoli, 1777, Pseudomystus Jayaram, 1968 and Sper- ata Holly, 1939) and more than 27 species are recorded from Thailand (Ferraris, 2007; Rainboth, 1996; Vidthayanon, 2005). Most species of the genera Hemibragus and Mystus are booming in aquaculture, with some of them being kept in the aquarium (Vidthayanon, 2005). However, cytogenetic studies in Thai bagrids ∗ Corresponding author at: Khon Kaen University, Department of Biology, Faculty of Science, 123 Mitraphap Highway, Khon Kaen 40002, Muang District, Thailand. Tel.: +66 82 3095690; fax: +66 4320 2530. E-mail address: raccha@kku.ac.th (A. Chaveerach). are quit scarce, in which only conventional technique reported to determine chromosome number and karyotype composition has been performed. Therefore, very little is known concerning its chro- mosomal evolution. Multiple DNA copies or repetitive DNAs are a large substan- tial portion of the genome of eukaryotes that can be generally classified into two main classes: tandem repeats, such as the multi- gene families and the satellite DNAs; and the dispersed elements, such as transposons and retrotransposons, known as Transpos- able elements (TEs) (Jurka et al., 2005). Among the tandem repeats we can find the highly-repeated satellite DNAs and “moderate repeats”, like mini- and microsatellite DNA (Charlesworth et al., 1994). These non-coding DNA sequences are organized as long arrays of head-to-tail linked repeats (Plohl et al., 2008). On the other hand, TEs are stretches of DNA that move around the genome, and the genomes of many higher organisms are abounding with numerous copies of these enigmatic elements (Biémont and Vieira, 2006). http://dx.doi.org/10.1016/j.jcz.2014.02.004 0044-5231/© 2014 Elsevier GmbH. All rights reserved.