Measurement of Chromosomal Arms and FISH Reveal Complex Genome Architecture and Standardized Karyotype of Model Fish, Genus Carassius

• Published in: Cells (Basel, Switzerland) Switzerland), 2021-09, Vol.10 (9), p.2343
• Main Authors: Knytl, Martin, Fornaini, Nicola Reinaldo
• Format: Article
• Language: English
• Subjects: Animals; Carassius; Carassius auratus; Carassius carassius; Carassius gibelio; Carps - genetics; chromosome; Chromosome Mapping - methods; Chromosomes - genetics; Cytogenetics; Diploids; Diploidy; Evolution; Female; Females; Fish; Fishes - genetics; Fluorescence in situ hybridization; Genetic Variation - genetics; Genome - genetics; Genomes; Goldfish - genetics; i value; in situ hybridization; In Situ Hybridization, Fluorescence - methods; karyogram; Karyotype; Karyotypes; Karyotyping - methods; Male; Morphology; Phylogeny; Polyploidy; q/p arm ratio; Sex chromosomes; Species
• ISSN: 2073-4409; 2073-4409
• DOI: 10.3390/cells10092343

The widely distributed ray-finned fish genus is very well known due to its unique biological characteristics such as polyploidy, clonality, and/or interspecies hybridization. These biological characteristics have enabled species to be successfully widespread over relatively short period of evolutionary time. Therefore, this fish model deserves to be the center of attention in the research field. Some studies have already described the karyotype, but results are inconsistent in the number of morphological categories for individual chromosomes. We investigated three focal species: , and with the aim to describe their standardized diploid karyotypes, and to study their evolutionary relationships using cytogenetic tools. We measured length (q+plength) of each chromosome and calculated centromeric index ( value). We found: (i) The relationship between q+plength and value showed higher similarity of and . (ii) The variability of value within each chromosome expressed by means of the first quartile (Q1) up to the third quartile (Q3) showed higher similarity of and . (iii) The fluorescent in situ hybridization (FISH) analysis revealed higher similarity of and . (iv) Standardized karyotype formula described using median value (Q2) showed differentiation among all investigated species: had 24 metacentric ( ), 40 submetacentric (sm), 2 subtelocentric (st), 2 acrocentric ( ) and 32 telocentric ( ) chromosomes (24m+40sm+2st+2a+32T); : 16m+34sm+8st+42T; and : 16m+22sm+10st+2a+50T. (v) We developed R scripts applicable for the description of standardized karyotype for any other species. The diverse results indicated unprecedented complex genomic and chromosomal architecture in the genus probably influenced by its unique biological characteristics which make the study of evolutionary relationships more difficult than it has been originally postulated.