Folia Zool. – 53(3): 329–334 (2004) Karyotypic characterization of bream, Abramis brama (Pisces, Cyprinidae) Konrad OCALEWICZ 1 , Malgorzata JANKUN 1* and Alicja BOROŃ 2 1 University of Warmia and Mazury in Olsztyn, Department of Evolutionary Genetics, 10-718 Olsztyn, Poland; e-mail: con@uwm.edu.pl, *mjpw@uwm.edu.pl 2 University of Warmia and Mazury in Olsztyn, Department of Zoology, 10-718 Olsztyn, Poland; e-mail: alibo@uwm.edu.pl Received 30 June 2003; Accepted 14 June 2004 A b s t r a c t . The karyotype of bream Abramis brama was analysed by means of C-banding, replication banding, DAPI fluorescent staining and in situ hybridisation with 18S rDNA and telomeric probes. The use of the in vivo 5-bromodeoxyuridine incorporation technique enabled the induction of replication bands of the RBA type in the karyotype. C-bands corresponded to late replicated chromosome regions. 18S rDNA clusters were found on one chromosome pair. Telomeric sequences were observed only on ends of chromatids. The karyotype morphology and NOR phenotype of A. brama are very similar to those found in other species of the leuciscine cyprinids karyotyped so far. Key words: chromosomes, Leuciscinae, rDNA, replication, telomere Introduction The bream Abramis brama (Cyprinidae, Cypriniformes) is one of the most abundant fish species in central Europe and Asia. Data on its chromosome complements have been reported by several authors (N y g r e n et al. 1975, B a r s h e n e 1977, B a r s h e n e et al. 1983, A r e f j e v & K a r n a u c h o v 1989). All these karyotype studies have been based on conventionally Giemsa-stained chromosomes. This paper is a continuation of our previous investigation on Abramis brama from Poland (J a n k u n et al. 1997). The aim of the present study was to describe the bream karyotype by means of replication, C-banding and molecular cytogenetics methods. Materials and Methods Nineteen adult bream (Abramis brama): 8 females and 11 males were caught with gill nets in Lake Kortowo in Olsztyn, Poland. Chromosome preparation was done according to R á b & R o t h (1988) with modifications described by J a n k u n et al. (1997). Replication banding followed the method described by J a n k u n et al. (1998). In vivo BrdU (Sigma) incubation equalled 6 h. C-banding was performed according to S u m n e r (1972) with alkaline denaturation at 50 °C for 2 minutes. In situ hybridization (ISH) using as a probe a plasmid including rDNA transcription unit and most of the 18S rRNA gene (pB18’) was done as described previously (J a n k u n et al. 2001). Chromosomes were stained with 4’, 6-diamidino-2-phenylindole (DAPI) using antifade (Vectashield Vector, Burlingame, USA) with DAPI. The telomere PNA probe (synthetic DNA/RNA analogue) conjugated * Corresponding author 329