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 distribution in Europe. Six males and six females of the species from the Baltic Sea basin in Poland were examined to 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 28S and 5S rDNA probes. The karyotype consisted of 20 m, 36 sm and 44 sta chromosomes, NF=156. The AgNO3 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 the regions. 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 of NORs suggested the scarcity of AT-rich DNA in the regions. FISH with 5S rDNA probe revealed 8–14 loci (ten and 12 in respectively 49 and 29% of metaphases). They were located in two sm and eight to ten 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 in different chromosomes. Molecular cytogenetic data of C. carassius presented here for the first time give an important insight into the structure of chromosomes of this polyploid and declining species and may be useful in its systematics.

Morphologically indistinguishable hybrid Carassius female with 156 chromosomes: A threat for the threatened crucian carp, C. carassius, L

“…28S rDNA genes, which make up the 45S rDNA (nucleolar organizer regions [NOR]-bearing) transcriptional unit, tandemly repeated with high copy numbers are useful markers for cytotaxonomic identification [ 71 ]. In accordance with Spoz et al [ 64 ], we found four 28S rDNA loci on a pair of sm and st-a chromosomes in both diploid male and triploid Carassius female. This pattern of four 28S rDNA loci and its identical chromosomal positioning (this study and [ 64 ]) shows that this region of the genome is highly conserved in C .…”

“…In accordance with Spoz et al [ 64 ], we found four 28S rDNA loci on a pair of sm and st-a chromosomes in both diploid male and triploid Carassius female. This pattern of four 28S rDNA loci and its identical chromosomal positioning (this study and [ 64 ]) shows that this region of the genome is highly conserved in C . carassius .…”

“…Our genetic analyses contributed to cytotaxonomy of the endangered C . carassius [ 25 , 64 ] and revealed a haploid C . carassius genome in a triploid hybrid combined with a diploid C .…”

“…In C . carassius with 100 chromosomes, Spoz et al [ 64 ] found eight to 14 5S rDNA loci on the p arms of sm chromosomes, and on the p arms or in a pericentromeric position of sm and st-a chromosomes. The most frequent number of 5S rDNA loci was 10, six of which gave strong signals and four gave weak signals.…”

Chromosomes of Asian cyprinid fishes: cytogenetic analysis of two representatives of small paleotetraploid tribe Probarbini

“…As an example, the common carp Cyprinus carpio , with a (paleo) tetraploid karyotype 2n = 100, exhibits a re-diploidized pattern for 45S rDNA, with only a single chromosome pair carrying such sites [92, 93]. Also four to eight 5S rDNA loci [94] can be observed there, while in the (paleo-) tetraploid crucian carp Carassius carassius the major rDNA sites occupy two different chromosomal pairs, and the minor rDNA encompasses a variable number of 8–18 loci [29, 30]. Besides, a comparable variability of rDNA distribution was also present in several polyploid forms of C. auratus complex [63, 67, 95].…”