Distinguishing between Incomplete Lineage Sorting and Genomic Introgressions : Complete Fixation of Allospecific Mitochondrial DNA in a Sexually Reproducing Fish (Cobitis; Teleostei), despite Clonal Reproduction of Hybrids

Peer reviewe

Cytogenetics, genomics and biodiversity of the South American and African Arapaimidae fish family (Teleostei, Osteoglossiformes)

<div><p>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 Arapaimidae, studying a unique fish model group with advanced molecular cytogenetic genomic tools. The aim is to better explore and clarify certain events and factors that had impact on evolutionary history of this fish group. For that, both South American and African representatives of Arapaimidae, namely <i>Arapaima gigas</i> and <i>Heterotis niloticus</i>, were examined. Both species differed markedly by diploid chromosome numbers, with 2n = 56 found in <i>A</i>. <i>gigas</i> and 2n = 40 exhibited by <i>H</i>. <i>niloticus</i>. Conventional cytogenetics along with fluorescence <i>in situ</i> hybridization revealed some general trends shared by most osteoglossiform species analyzed thus far, such as the presence of only one chromosome pair bearing 18S and 5S rDNA sites and karyotypes dominated by acrocentric chromosomes, resembling thus the patterns of hypothetical ancestral teleost karyotype. Furthermore, the genomes of <i>A</i>. <i>gigas</i> and <i>H</i>. <i>niloticus</i> display remarkable divergence in terms of repetitive DNA content and distribution, as revealed by comparative genomic hybridization (CGH). On the other hand, genomic diversity of single copy sequences studied through principal component analyses (PCA) based on SNP alleles genotyped by the DArT seq procedure demonstrated a very low genetic distance between the South American and African Arapaimidae species; this pattern contrasts sharply with the scenario found in other osteoglossiform species. Underlying evolutionary mechanisms potentially explaining the obtained data have been suggested and discussed.</p></div

Karyotype and chromosome banding of endangered crucian carp, Carassius carassius (Linnaeus, 1758) (Teleostei, Cyprinidae)

Volume: 7Start Page: 205End Page: 21

Karyotype of Sabanejewia bulgarica (Drensky, 1928) (Teleostei, Cobitidae) from the Danube Delta, Romania

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 pairs of subtelocentric to acrocentric chromosomes. Pericentromeric blocks of heterochromatin were revealed in most of the chromosome pairs. The karyotype phenotype of S. bulgarica was the same as found for S. balcanica from Northern Carpathian Mountains

Karyotype and chromosomal characteristics of rDNA of Cobitis strumicae Karaman, 1955 (Teleostei, Cobitidae) from Lake Volvi, Greece

International audienceThe karyotype of Greek cobitid fish Cobitis strumicae 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, CMA3 fluorescence banding and also by in situ hybridization (FISH) with rDNA probe. The diploid chromosome number was 2n = 50, karyotype composed of 10 pairs of metacentric to submetacentric and 15 pairs of subtelocentric to acrocentric chromosomes. The nucleolus organizer regions (NORs) as revealed by Ag- and CMA3 staining and FISH were situated in the telomeric region of the fourth submetacentric chromosome pair. The chromosomes contained very low content of C-positive heterochromatin. No heteromorphic sex chromosomes were detected. This first karyotype report for any species of lineage Bicanestrinia Băcescu, 1962 shows a simple karyotype dominated by acrocentric chromosomes and possessing single NOR-bearing chromosome pair. Cytotaxonomic implications of this finding for the taxonomy of the genus Cobitis Linnaeus, 1758 are further discussed

Posterior probability distributions for migration rates from two-population IM analysis.

<p>Coalescent-based estimates of migration rates (scaled by mutation rate) for three studied species inferred separately from (A–C) nuclear sequence data that included nine nuclear markers, and from (D–H) one mitochondrial marker gene.</p

Spined loaches (<i>Cobitis</i>) used in this study.

<p>Spined loaches (<i>Cobitis</i>) used in this study.</p