Petr Ráb

• The Czech Academy of Sciences

The barbels of the subfamilies ´Poropuntinae´ and Smiliogastrinae within the family Cyprinidae play a significant role as a food source for fish in artisanal fisheries and are highly valued as ornamental fish in Thailand. In this study, we employed both conventional and molecular cytogenetics to analyze the karyotype of 15 fish species from two cyp...

Most eukaryotes maintain the stability of their cellular genome sizes to ensure genome transmission to offspring through sexual reproduction. However, some alter their genome size by selectively eliminating parts or increasing ploidy at specific developmental stages. This phenomenon of genome elimination or whole genome duplication occurs in animal...

Sex chromosomes of teleost fishes often have low levels of differentiation and undergo frequent turnovers. Annual Nothobranchius killifishes comprise representatives with male-heterogametic XY or X1X2Y sex chromosome systems, scattered across their phylogeny, nested within species lacking cytologically detectable sex chromosomes. They thus provide...

The Labeoninae subfamily is a highly diversified but demonstrably monophyletic lineage of cyprinid fishes comprising five tribes and six incertae sedis genera. This widely distributed assemblage contains some 48 genera and around 480 recognized species distributed in freshwaters of Africa and Asia. In this study, the karyotypes and other chromosoma...

Karyotype divergence may strongly affect the degree of hybridization between species. Western Palearctic slow worms (Anguis) are legless lizards forming different types of secondary contact zones. To identify the level of chromosomal variation in slow worms, we examined karyotype in multiple populations of all species except one and Pseudopus apodu...

Using African annual killifishes of the genus Nothobranchius from temporary savannah pools with rapid karyotype and sex chromosome evolution, we analysed the chromosomal distribution of telomeric (TTAGGG)n repeat and Nfu‐SatC satellite DNA (satDNA; isolated from Nothobranchius furzeri) in 15 species across the Nothobranchius killifish phylogeny, an...

The neotropical region exhibits the greatest worldwide biodiversity, with species diversification history being related to the puzzling geomorphologic and climatic history of this region. About 6000 fish species inhabit the Neotropics, representing one of the richest ichthyofaunas in the world, both in terms of the number and taxonomic diversity of...

The karyotype of the freshwater fish Sabanejewia bulgarica (Drensky, 1928), from the Danube Delta, was studied by conventional Giemsa staining and the C-banding technique. The diploid chromosome number was 2n = 50. The karyotype contained 2 pairs of metacentric (the first one was much larger than the second one), 6 pairs of submetacentric and 17 pa...

Scleropages formosus (Osteoglossiformes, Teleostei) represents one of the most valued ornamental fishes, yet it is critically endangered due to overexploitation and habitat destruction. This species encompasses three major color groups that naturally occur in allopatric populations, but the evolutionary and taxonomic relationships of S. formosus co...

Simple Summary All Poropuntiinae fish species are diploid and have 50 chromosomes in their cells; however, their karyotypes differ (the organization of chromosomes according to size and shape). The goal of this study is to compare the genomic differences between their conserved karyotypes using conventional and molecular cytogenetic methods. We fou...

Repetitive DNA may have significant impact on genome evolution. African annual killifishes of the genus Nothobranchius (Teleostei: Nothobranchiidae), which has adapted to temporary water pools in African savannahs, possess genomes with high repeat content. They are also characterized by rapid karyotype and sex chromosome evolution but the role of g...

Miniature refers to species with extraordinarily small adult body size when adult and can be found within all major metazoan groups. It is considered that miniature species have experienced severe alteration of numerous morphological traits during evolution. For a variety of reasons, including severe labor concerns during collecting, chromosomal ac...

Karyotype divergence may strongly affect the rate of hybridization between species in their secondary contact zones. Slow worms ( Anguis , Anguidae) are morphologically relatively cryptic legless lizards representing two evolutionary lineages, A. cephallonica from the southernmost Balkans, and the A. fragilis species complex (comprising two sister-...

Homomorphic sex chromosomes and their turnover are common in teleosts. We investigated the evolution of nascent sex chromosomes in several populations of two sister species of African annual killifishes, Nothobranchius furzeri and N. kadleci, focusing on their under-studied repetitive landscape. We combined bioinformatic analyses of the repeatome w...

Repetitive DNA represents an important driver of sex chromosome differentiation. Yet, repetitive sequences tend to be misrepresented or overlooked in genomic studies. We analysed repetitive DNA landscape of sex chromosomes in several populations of a turquoise killifish Nothobranchius furzeri and its sister species N. kadleci (Teleostei: Nothobranc...

Teleost fishes exhibit a breath-taking diversity of sex determination and differentiation mechanisms. They encompass at least nine sex chromosome systems with often low degree of differentiation, high rate of inter- and intra-specific variability, and frequent turnovers. Nevertheless, several mainly female heterogametic systems at an advanced stage...

Freshwater fishes of the superfamily Cobitoidea are a species-rich group that are present in virtually every river in Europe and Asia. Three of the nine recognized families show massive karyotype reconstructions, including several independent cases of polyploidy, indicating cytogenetic evolution correlated with their diversification. We herein pres...

Despite decades of cytogenetic and genomic research of dynamic sex chromosome evolution in teleost fishes, multiple sex chromosomes have been largely neglected. In this review, we compiled available data on teleost multiple sex chromosomes, identified major trends in their evolution and suggest further trajectories in their investigation. In a comp...

Although crocodilians have attracted enormous attention in other research fields, from the cytogenetic point of view, this group remains understudied. Here, we analyzed the karyotypes of eight species formally described from the Alligatoridae family using differential staining, fluorescence in situ hybridization with rDNA and repetitive motifs as a...

Metazoans usually reproduce sexually, blending the unique identity of parental genomes for the next generation through functional crossing-over and recombination in meiosis. However, some metazoan lineages have evolved reproductive systems where offspring are either full (clonal) or partial (hemiclonal) genetic replicas. In the latter group, the pr...

Salmonids are extremely important economically and scientifically; therefore, dynamic developments in their research have occurred and will continue occurring in the future. At the same time, their complex phylogeny and taxonomy are challenging for traditional approaches in research. Here, we first provide discoveries regarding the hitherto complet...

The South American giant fishes of the genus Arapaima, commonly known as pirarucu, are one of the most iconic among Osteoglossiformes. Previously cytogenetic studies have identified their karyotype characteristics; however, characterization of cytotaxonomic differentiation across their distribution range remains unknown. In this study, we compared...

Critically endangered sturgeons, having undergone three whole genome duplication events, represent an exceptional example of ploidy plasticity in vertebrates. Three extant ploidy groups, combined with autopolyploidization, interspecific hybridization and the fertility of hybrids are important issues in sturgeon conservation and aquaculture. Here we...

The Cyprinidae family is a highly diversified but demonstrably monophyletic lineage of cypriniform fishes. Among them, the genus Osteochilus contains 35 recognized valid species distributed from India, throughout Myanmar, Laos, Thailand, Malaysia, Indonesian archipelago to southern China. In this study, karyotypes and other chromosomal characterist...

Rainbowfishes (Melanotaeniidae) are the largest monophyletic group of freshwater fishes occurring in Australia and New Guinea, with 112 species currently recognised. Despite their high taxonomic diversity, rainbowfishes remain poorly studied from a cytogenetic perspective. Using conventional (Giemsa staining, C banding, chromomycin A3 staining) and...

The Neotropical region exhibits the greatest worldwide diversity and the diversification history of several clades is related to the puzzling geomorphologic and climatic history of this region. The freshwater Amazon ecoregion contains the main hydrographic basins of the Neotropical region that are highly dendritic and ecologically diverse. It conta...

The bighead carps of the genus Hypophthalmichthys (H. molitrix and H. nobilis) are important aquaculture species. They were subjected to extensive multidisciplinary research, but with cytogenetics confined to conventional protocols only. Here, we employed Giemsa-/C-/CMA3- stainings and chromosomal mapping of multigene families and telomeric repeats...

Lebiasinidae fishes have been historically neglected by cytogenetical studies. Here we present a genomic comparison in eleven Lebiasinidae species, in addition to a review of the ribosomal DNA sequences distribution in this family. With that, we develop ten sets of experiments in order to hybridize the genomic DNA of representative species from the...

Lebiasinidae is a Neotropical freshwater family widely distributed throughout South and Central America. Due to their often very small body size, Lebiasinidae species are cytogenetically challenging and hence largely underexplored. However, the available but limited karyotype data already suggested a high interspecific variability in the diploid ch...

Lebiasinidae is a small fish family composed by miniature to small-sized fishes with few cytogenetic data (most of them limited to descriptions of diploid chromosome numbers), thus preventing any evolutionary comparative studies at the chromosomal level. In the present study, we are providing, the first cytogenetic data for the red spotted tetra, C...

Cichlid fishes are the subject of scientific interest because of their rapid adaptive radiation, resulting in extensive ecological and taxonomic diversity. In this study, we examined 11 morphologically distinct cichlid species endemic to Barombi Mbo, the largest crater lake in western Cameroon, namely Konia eisentrauti, Konia dikume, Myaka myaka, P...

The South American arowanas (Osteoglossiformes, Osteoglossidae, Osteoglossum) are emblematic species widely distributed in the Amazon and surrounding basins. Arowana species are under strong anthropogenic pressure as they are extensively exploited for ornamental and food purposes. Until now, limited genetic and cytogenetic information has been avai...

Arowanas (Osteoglossinae) are charismatic freshwater fishes with six species and two genera (Osteoglossum and Scleropages) distributed in South America, Asia, and Australia. In an attempt to provide a better assessment of the processes shaping their evolution, we employed a set of cytogenetic and genomic approaches, including i) molecular cytogenet...

Although fishes have traditionally been the subject of comparative evolutionary studies, few reports have concentrated on the application of multipronged modern molecular cytogenetic techniques (such as comparative genomic hybridization = CGH and whole chromosome painting = WCP) to analyze deeper the karyotype evolution of specific groups, especial...

Belonging to the order Atheriniformes, Craterocephalus is one of the most widespread genera of freshwater fishes in Australia, spanning along the northern coast from central Western Australia to central New South Wales and across the Murray-Darling and Lake Eyre basins. In this study, both conventional cytogenetic techniques (Giemsa, C-banding, CMA...

The catfish family Siluridae contains 107 described species distributed in Asia, but with some distributed in Europe. In this study, karyotypes and other chromosomal characteristics of 15 species from eight genera were examined using conventional and molecular cytogenetic protocols. Our results showed the diploid number (2n) to be highly divergent...

Belonging to the order Atheriniformes, Craterocephalus is one of the most widespread genera of freshwater fishes in Australia, spanning along the northern coast from central Western Australia to central New South Wales and across the Murray-Darling and Lake Eyre basins. In this study, both conventional cytogenetic techniques (Giemsa, C-banding), CM...

Belonging to the order Atheriniformes, Craterocephalus is one of the most widespread genera of freshwater fishes in Australia, spanning along the northern coast from central Western Australia to central New South Wales and across the Murray-Darling and Lake Eyre basins. In this study, both conventional cytogenetic techniques (Giemsa, C-banding), CM...

Osteoglossiformes represents one of the most ancestral teleost lineages, currently widespread over almost all continents, except for Antarctica. However, data involving advanced molecular cytogenetics or comparative genomics are yet largely limited for this fish group. Therefore, the present investigations focus on the osteoglossiform family Arapai...

List of all SNP data generated by DArTseq. FreqHomRef represents frequency of homozygotes for reference allele (more common major allele), FreqHomSnp represents frequency of homozygotes for SNP allele (less common minor allele), and FreqHets represents frequency of heterozygotes (CSV)

Detailed protocol for chromosomal obtainment in Arapaimidae fishes. (DOCX)

Notopteridae (Teleostei, Osteoglossiformes) represents an old fish lineage with ten currently recognized species distributed in African and Southeastern Asian rivers. Their karyotype structures and diploid numbers remained conserved over long evolutionary periods, since African and Asian lineages diverged approximately 120 Mya. However, a significa...

Despite their long history with the basal split dating back to the Eocene, all species of monitor lizards (family Varanidae) studied so far share the same chromosome number of 2n = 40. However, there are differences in the morphology of the macrochromosome pairs 5–8. Further, sex determination, which revealed ZZ/ZW sex microchromosomes, was studied...

Purpose of Review Fishes exhibit the greatest biodiversity among extant vertebrates. In fact, about 34,000 fish species are currently estimated, of which ~ 25% are living in Neotropical freshwaters. Currently, several leading-edge studies using molecular biology procedures have largely contributed to the investigation of the fish genomic architectu...

The karyotype of Greek cobitid fish Cobitisstrumicae Karaman, 1955, from Lake Volvi, Greece, a representative of one of its two major intraspecific phylogenetic lineages, was analysed by means of sequential Giemsa-staining, C-banding, silver-staining, CMA 3 fluorescence banding and also by in situ hybridization (FISH) with rDNA probe. The diploid c...

Background Polyploidy, although still poorly explored, represents an important evolutionary event in several cyprinid clades. Herein, Catlocarpio siamensis and Probarbus jullieni - representatives of the paleotetraploid tribe Probarbini, were characterized both by conventional and molecular cytogenetic methods. Results Alike most other paleotetrap...

Osteoglossiformes is one of the most ancient (Early Triassic) groups of freshwater teleosts and has at least one representative on each continent of the Southern Hemisphere, with the exception of Antarctica. Among its six described families, the Gymnarchidae occurs in many African rivers, including the river Nile, where Gymnarchus niloticus is its...

In addition to its wide geographical distribution, osteoglossiform fishes represent one of the most ancient freshwater teleost lineages; making it an important group for systematic and evolutionary studies. These fishes had a Gondwanan origin and their past distribution may have contributed to the diversity present in this group. However, cytogenet...

Polyploidization has played an important role in the evolution of vertebrates, particularly at the base of Teleostei–an enormously successful ray-finned fish group with additional genome doublings on lower taxonomic levels. The investigation of post-polyploid genome dynamics might provide important clues about the evolution and ecology of respectiv...

FISH with 5S rDNA and U2 snDNA probes in the rest of examined botiid species. U2 snDNA (red, arrows) and 5S rDNA (green, arrowheads) probes (B,F,H) or a single U2 snDNA (red, arrows) probe (A,C,D,E,G) mapped on (A) B. almorhae, (B) Ch. macracanthus, (C) L. elongata, (D) L. guilinensis, (E) P. fasciatus, (F) S. pulchra, (G) S. superciliaris, (H) S....

PNA FISH with telomeric probe in the rest of examined botiid species. (A) B. udomritthiruji, (B) S. pulchra, (C) S. superciliaris, (D) S. zebra, (E) Y. lecontei. For better contrast, pictures were pseudocoloured in green (telomeric repeat probe) and red (DAPI). For better distinction between individual chromosomes, we included also the separate ima...

Selected sequential experiments clarifying conjugated or independent location of distinct cytogenetic markers. Metaphases are arranged sequentially in Ch. macracanthus (A,D), L. elongata (B,E), L. guilinensis (C,F), L. microphthalma (G,I) and S. superciliaris (H,J) after CMA3/DAPI staining (D,E,F,I,J) and corresponding dual-colour FISH with 28S rDN...

Karyotype and mitotic chromosomes of B. dario after different cytogenetic protocols. (A) Karyotype arranged from Giemsa-stained chromosomes, (B) CMA3/DAPI staining. (C) Dual-colour FISH with 28S rDNA (red, arrows) and 5S rDNA (green, arrowheads) probes. (D) Uni-colour FISH with U2 snDNA (red, arrows) probe. (E) PNA FISH with telomeric probe. Due to...

CMA3/DAPI staining in the rest of examined botiid species. (A) B. udomritthiruji, (B) L. elongata, (C) P. fasciatus, (D) S. superciliaris, (E) S. zebra, (F) Y. lecontei. For better contrast, pictures were pseudocoloured in red (for CMA3) and green (for DAPI). Open arrows indicate CMA3-positive sites. The metaphase spread of S. superciliaris (D) is...

Dual-colour (5S/45S) rDNA FISH in the rest of examined botiid species. 28S rDNA (red, arrows) and 5S rDNA (green, arrowheads) probes mapped on (A) L. elongata, (B) L. microphthalma, (C) S. superciliaris, (D) S. zebra, (E) Y. lecontei. Chromosomes were counterstained with DAPI (blue). Note the significant spreading of 5S rDNA sites in Y. lecontei (E...

The Erythrinidae family (Teleostei: Characiformes) is a small Neotropical fish group with a wide distribution throughout South America, where Hoplias malabaricus corresponds to the most widespread and cytogenetically studied taxon. This species possesses significant genetic variation, as well as huge karyotype diversity among populations, as reflec...

The Neotropical fish, Hoplias malabaricus, is one of the most cytogenetically studied fish taxon with seven distinct karyomorphs (A–G) comprising varying degrees of sex chromosome differentiation, ranging from homomorphic to highly differentiated simple and multiple sex chromosomes. Therefore, this fish offers a unique opportunity to track evolutio...

The crucian carp Carassius carassius (Linnaeus, 1758), is native to many European freshwaters. Despite its wide distribution, the crucian carp is declining in both the number and sizes of populations across much of its range. Here we studied 30 individuals of a putative pure population from Helsinki, Finland. Despite clear external morphological fe...

Background Acipenseriformes is a basal lineage of ray-finned fishes and comprise 27 extant species of sturgeons and paddlefishes. They are characterized by several specific genomic features as broad ploidy variation, high chromosome numbers, presence of numerous microchromosomes and propensity to interspecific hybridization. The presumed palaeotetr...

Bowfin belongs to an ancient lineage of nonteleost ray-finned fishes (actinopterygians) and is the only extant survivor of a once diverged group, the Halecomorphi or Amiiformes. Owing to the scarcity of extant nonteleost ray-finned lineages, also referred as "living fossils," their phylogenetic interrelationships have been the target of multiple hy...

Genomic GC content can vary locally, and GC-rich regions are usually associated with increased DNA thermostability in thermophilic prokaryotes and warm-blooded eukaryotes. Among vertebrates, fish and amphibians appeared to possess a distinctly less heterogeneous AT/GC organization in their genomes, whereas cytogenetically detectable GC heterogeneit...

One of the five basal actinopterygian lineages, the Chondrostei, including sturgeon, shovelnose, and paddlefish (Order Acipenseriformes) show extraordinary ploidy diversity associated with three rounds of lineage-specific whole-genome duplication, resulting in three levels of ploidy in sturgeon. Recently, incidence of spontaneous polyploidization h...

The monophyletic order Osteoglossiformes represents one of the most ancestral groups of teleosts and has at least 1 representative in all continents of the southern hemisphere, with the exception of Antarctica. However, despite its phylogenetic and biogeographical importance, cytogenetic data in Osteoglossiformes are scarce. Here, karyotype and chr...

The role of chromosome changes in speciation remains a debated topic, although demographic conditions associated with divergence should promote their appearance. We tested a potential relationship between chromosome changes and speciation by studying two Lake Whitefish (Coregonus clupeaformis) lineages that recently colonized post-glacial lakes fol...

One of the most efficient mechanisms to keep animal lineages separate is a difference in ploidy level (number of whole genome copies), since hybrid offspring from parents with different ploidy level are functionally sterile. In the freshwater fish family Botiidae, ploidy difference has been held responsible for the separation of its two subfamilies...

Background: The ability to eliminate a parental genome from a eukaryotic germ cell is a phenomenon observed mostly in hybrid organisms displaying an alternative propagation to sexual reproduction. For most taxa, the underlying cellular pathways and timing of the elimination process is only poorly understood. In the water frog hybrid Pelophylax esc...

Interspecific hybridization, polyploidization and transitions from sexuality to asexuality considerably affect organismal genomes. Especially the last mentioned process has been assumed to play a significant role in the initiation of chromosomal rearrangements, causing increased rates of karyotype evolution. We used cytogenetic analysis and molecul...

Hybrid individuals used for karyotyping presented in S1 Fig. (DOCX)

List of hybrid individuals used for GISH experiments presented in S3 Fig. (DOCX)

Representative karyotypes of hybrid biotypes after DAPI/Giemsa staining. (A-C) EN hybrids. (D-F) EEN hybrids. (G-I) ENN hybrids. (J-L) ET hybrids. (M-O) EET hybrids. (P-R) ETT hybrids. Chromosomes were arranged in a decreasing size order and classified in four morphological groups: metacentric (m), submetacentric (sm), subtelocentric (st) and acroc...

Maximum likelihood phylogenetic tree of Cobitis and Sabanejewia species. ML phylogenetic tree constructed from cytochrome b gene sequences from Tang et al. [46] and from Doadrio and Perdices [47]. Calibration point follows Doadrio and Perdices [47]. Widths of branches are proportional to ML estimate of substitution rate. Cobitis species are highlig...

Hybrid individuals used for GISH experiments presented in Fig 1. (DOCX)

Representative metaphases of hybrid biotypes after GISH experiments. (A, B) EN hybrids. (C, D) EEN hybrids. (E, F) ENN hybrids. (G, H) ET hybrids. (I, J) EET hybrids. (K, L) ETT hybrids. Probes labelled with biotin-16-dUTP were detected with streptavidin-FITC (green signals on chromosomes); probes labelled with digoxigenin-11-dUTP were detected wit...

Background: Loaches of the family Nemacheilidae are one of the most speciose elements of Palearctic freshwater ichthyofauna and have undergone rapid ecological adaptations and colonizations. Their cytotaxonomy is largely unexplored; with the impact of cytogenetical changes on this evolutionary diversification still unknown. An extensive cytogeneti...

One of the most efficient mechanisms to keep animal lineages separate is a difference in ploidy level, since hybrid offspring from parents with different ploidy level are generally sterile. In the freshwater fish family Botiidae, ploidy difference has been held responsible for the separation of its two subfamilies, the tetraploid Botiinae and the d...