Event Abstract

Comparison of 5S rDNA structure and its chromosomal localization in Carassius (Pisces, Cyprinidae) taxa

  • 1 Department of Zoology, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Poland
  • 2 University of Warmia and Mazury in Olsztyn, Poland

Genus Carassius belongs to the subfamily Cyprininae including more than 1300 species. Most of them characterize by diploid number of 50 chromosome which is indicated as synapomorphic state for Actinopterygii. Others, around 400 are closely related polyploid species, tetraploids (2n=ca. 100) or hexaploids (2n=ca. 150) originated via polyploidization and then returned to a diploid state via rediploidization. Two Carassius species are distributed in the Polish inland waters, C. gibelio (Bloch, 1782) of Asian origin and native C. carassius (Linnaeus, 1758). As the most invasive freshwater species in Europe, C. gibelio is considered the most abundant alien and invasive species in Polish ichthyofauna. C. gibelio is commonly regarded as one form of the polyploid C. auratus complex. The crucian carp, C. carassius is included in the least concern IUCN category but is regarded as disappearing; its distribution rate in Poland decreased during the last two decades. Moreover, bisexually reproducing C. gibelio may create better adapted viable hybrids, e.g. with C. carassius which may lead to displacement of C. carassius genome by genomes of hybrids. So, it is important to determine the diagnostic features of both these species. Ribosomal genes (rDNA) due to high rates of transcription and recombination contribute to genome diversification (Symonová and Howell 2018). In higher eukaryotes, 5S rDNA sequence is organized in repetitive units consisting of a highly conserved coding sequence of 120 base pair (bp) which is adjacent to a non-transcribed spacer (NTS) showing a higher mutation rate and variations in length and nucleotide composition. Thus, 5S rDNAs are used as valuable markers for species and hybrids identification, inter- and intraspecific variation, genome evolution and phylogeny. So, the aim of this study was comparative analysis of 5S rDNAs and its chromosomal location in C. carassius and C. gibelio diploids and triploids (Szabelska et al. 2017) to contribute to the knowledge of their taxonomic features and relationships, and also to the understanding the dynamics of the changes along repetitive sequences in the genomes originated with the polyploidization. All samples of both the species were collected from the Siemianówka Reservoir (Poland) (52°55’N, 23°48’E) during commercially fishing and fin clips were collected post mortem. The kidney cell suspensions used for making the chromosome slides were obtained for previous studies (Spóz et al. 2014; Szabelska et al. 2017); all the experimental procedures were provided according to the positive opinion (No. 20/2013/N) of the Local Ethics Committee of the University of Warmia and Mazury in Olsztyn (UWM), Poland. Fin clips were preserved in 96% ethanol, stored at -20°C for further DNA extraction and 5S rDNA analysis done according to Szabelska et al. (2017). Double-colour FISH was performed according to Boroń et al. (2006). Two classes of 5S rDNA were detected in C. carassius (200 bp, class I; 380 bp, class II) and in C. gibelio (340 bp, class I; 470 bp, class II) taxa. These species differed significantly both within the coding sequences and NTS regions of two 5S rDNA classes due to single base differences. The differences in the form of indel changes of between the both species were identified within the 120 bp of coding region: in A Box, IE, C box and 3` end-coding region. Moreover, two common TATA-like elements among NTS were identified for all aligned 5S rDNA sequences of both Carassius taxa. The obtained consensus sequences were deposited into the GenBank. FISH with C. carassius 5S rDNA of 200 bp and 380 bp used as probes revealed a modal number of ten hybridization signals and two of them located on submetacentric chromosomes were stronger than the others. In turn, FISH with C. gibelio 5S rDNAs of 340 bp and 470 bp used as probes shown two strong signals on submetacentric chromosomes and 16 other weaker signals, whereas triploids possessed a modal number of 18 hybridization sides and three of them on submetacentrics, were stronger than the others. Both classes of 5S rDNA sequence were located in synteny. These results confirmed the usefulness of 5S rDNA chromosomal location for ploidy identification of C. gibelio. The observed variability of 5S rDNAs occurs as a good tool for species-specific investigation in karyologically varied Carassius diploids and polyploids, including hybrids. Apart from taxonomical data, the presented results contribute to the elucidation of the level complexity of 5S rDNA organization and improve our knowledge on chromosomal diversification involving diploid and polyploid taxa.


We express our thanks to the Polish Angling Association in Bialystok and Mr. Andrzej Filinowicz for collecting fish. This work was carried out within the projects no. 12.610.006-300 and 12.620.042-300 of the UWM in Olsztyn, financed by Ministry of Science and Higher Education, Poland.


1. Boroń, A., Szlachciak, J., Juchno, D., Grabowska, A., Jagusztyn, B., Porycka, K. 2011. Karyotype, morphology, and reproduction ability of the Prussian carp, Carassius gibelio (Actinopterygii: Cypriniformes: Cyprinidae), from unisexual and bisexual populations in Poland. Acta Ichthyologica et Piscatoria 41(1):19-28. doi: 10.3750/AIP2011.41.1.04 2.Knytl, M., Kalous, L., Rylková, K., Choleva, L., Merilä, J., Ráb, P. 2018. Morphologically indistinguishable hybrid Carassius female with 156 chromosomes: A threat for the threatened crucian carp, C. carassius, L. PLoS ONE 13(1): doi: 10.1371/journal.pone.0190924 3. Spóz, A., Boroń, A., Porycka, P., Karolewska, M., Ito, D., Abe, S., Kirtiklis, L., Juchno, D. 2014. Molecular cytogenetic analysis of the crucian carp, Carassius carassius (Linnaeus, 1758) (Teleostei, Cyprinidae), using chromosome staining and fluorescence in situ hybridisation with rDNA probes. Comp Cytogenet. 8(3): 233–248. doi: 10.3897/CompCytogen.v8i3.7718 4. Symonová, R.; Howell, W.M. Vertebrate Genome Evolution in the Light of Fish Cytogenomics and rDNAomics. Genes 2018, 9, 96. 5. Szabelska A., Kirtiklis L., Przybył A., Boroń A. 2017. 5S rDNA sequence shows differences between diploid and triploid Prussian carp Carassius gibelio (Teleostei, Cyprinidae). Turkish Journal of Fisheries and Aquatic Sciences 17:1127-1133. doi: 10.4194/1303-2712-v17_6_06

Keywords: 5S rDNA, Carassius, Diploids, Triploids, NTS, rDNAs

Conference: XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019.

Presentation Type: Poster


Citation: Szabelska A, Kirtiklis L, Przybył A and Boron A (2019). Comparison of 5S rDNA structure and its chromosomal localization in Carassius (Pisces, Cyprinidae) taxa. Front. Mar. Sci. Conference Abstract: XVI European Congress of Ichthyology. doi: 10.3389/conf.fmars.2019.07.00155

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Received: 28 May 2019; Published Online: 14 Aug 2019.

* Correspondence: PhD. Aleksandra Szabelska, Department of Zoology, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Olsztyn, Warmian-Masurian, 10-718, Poland, aleksandra.szabelska@uwm.edu.pl