Molecular cytogenetic analysis of the crucian carp, carassius carassius (linnaeus, 1758) (teleostei, cyprinidae), Using chromosome staining and fluorescence in situ hybridisation with rDNA probes

Abstract

The crucian carp Carassius carassius (Linnaeus, 1758) is a species with restricted and decreasing distributionin Europe. Six males and six females of the species from the Baltic Sea basin in Poland were examinedto show sequentially CMA3/AgNO3 staining pattern, DAPI staining, and, for the first time in literature,molecular cytogenetic analysis using double-colour fluorescence in situ hybridisation (FISH) with 28Sand 5S rDNA probes. The karyotype consisted of 20 m, 36 sm and 44 sta chromosomes, NF=156. TheAgNO3 stained NORs were most frequently located terminally in the short arms of two sm and two sta elements,and CMA3-positive sites were also observed suggesting abundant GC-rich repetitive DNA in theregions. Other CMA3-positive sites in the short arms of six to ten sm and sta chromosomes were detected.The results based on 28S rDNA FISH confirmed the location of rDNA sites. DAPI-negative staining ofNORs suggested the scarcity of AT-rich DNA in the regions. FISH with 5S rDNA probe revealed 8-14loci (ten and 12 in respectively 49 and 29% of metaphases). They were located in two sm and eight toten sta chromosomes and six of them were larger than others. Simultaneously, mapping of the two rDNA families on the chromosomes of C. carassius revealed that both 28S and 5S rDNA probes were located indifferent chromosomes. Molecular cytogenetic data of C. carassius presented here for the first time give animportant insight into the structure of chromosomes of this polyploid and declining species and may beuseful in its systematics.