XX/XY sex chromosome system and chromosome markers in the snake eel <i>Ophisurus serpens</i> (Anguilliformes: Ophichtidae)

Salvadori, Susanna; Deiana, Anna Maria; Deidda, Federica; Lobina, Cinzia; Mulas, Antonello; Coluccia, Elisabetta

doi:10.1080/17451000.2017.1406665

Cited by 8 publications

(7 citation statements)

References 46 publications

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“…The position of this region is noteworthy since a large NOR is found in the corresponding homologous region on the X chromosome, leading to the considerable size difference between both sex chromosomes (Born and Bertollo, 2000 ). Therefore, we are dealing here with an unusual situation, resembling the findings in weakly electric fish Eigenmannia virescens (de Almeida-Toledo and Foresti, 2001 ; Henning et al, 2008 ) or in the snake eel Ophisurus serpens (Salvadori et al, 2018 ), where the accumulation of rDNA and other repetitive DNAs occurs also on the X instead of Y chromosome. In our specific case, the sex-specific region is present on the corresponding C-positive but NOR-negative (Born and Bertollo, 2000 ; Cioffi et al, 2010 ) region on the Y chromosome.…”

Section: Discussionmentioning

confidence: 57%

Sex Chromosome Evolution and Genomic Divergence in the Fish Hoplias malabaricus (Characiformes, Erythrinidae)

et al. 2018

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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 reflected by its seven major karyotype forms (i.e., karyomorphs A-G) identified up to now. Although morphological differences in their bodies are not outstanding, H. malabaricus karyomorphs are easily identified by differences in 2n, morphology and size of chromosomes, as well as by distinct evolutionary steps of sex chromosomes development. Here, we performed comparative genomic hybridization (CGH) to analyse both the intra- and inter-genomic status in terms of repetitive DNA divergence among all but one (E) H. malabaricus karyomorphs. Our results indicated that they have close relationships, but with evolutionary divergences among their genomes, yielding a range of non-overlapping karyomorph-specific signals. Besides, male-specific regions were uncovered on the sex chromosomes, confirming their differential evolutionary trajectories. In conclusion, the hypothesis that H. malabaricus karyomorphs are result of speciation events was strengthened.

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Section: Discussionmentioning

confidence: 57%

Sex Chromosome Evolution and Genomic Divergence in the Fish Hoplias malabaricus (Characiformes, Erythrinidae)

et al. 2018

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“…Despite its high resolution in mammals, replication banding patterns have been produced in a limited number of fish species so far. Application of FPG enabled the identification of early and late replicating chromosomal regions with high resolution banding patterns in salmonids [ 15 , 16 ], white sturgeon [ 16 ], and eels [ 17 , 18 ]. Less clear patterns after BrdU incorporation were observed on chromosomes of cyprinids [ 19 , 20 ], anastomids [ 21 ], ictalurids [ 22 ], flatfish [ 23 ], pufferfish [ 24 ] and characids [ 25 ].…”

Section: Introductionmentioning

confidence: 99%

GC and Repeats Profiling along Chromosomes—The Future of Fish Compositional Cytogenomics

Matoulek

Borůvková

Ocalewicz

et al. 2020

Genes

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The study of fish cytogenetics has been impeded by the inability to produce G-bands that could assign chromosomes to their homologous pairs. Thus, the majority of karyotypes published have been estimated based on morphological similarities of chromosomes. The reason why chromosome G-banding does not work in fish remains elusive. However, the recent increase in the number of fish genomes assembled to the chromosome level provides a way to analyse this issue. We have developed a Python tool to visualize and quantify GC percentage (GC%) of both repeats and unique DNA along chromosomes using a non-overlapping sliding window approach. Our tool profiles GC% and simultaneously plots the proportion of repeats (rep%) in a color scale (or vice versa). Hence, it is possible to assess the contribution of repeats to the total GC%. The main differences are the GC% of repeats homogenizing the overall GC% along fish chromosomes and a greater range of GC% scattered along fish chromosomes. This may explain the inability to produce G-banding in fish. We also show an occasional banding pattern along the chromosomes in some fish that probably cannot be detected with traditional qualitative cytogenetic methods.

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“…Despite centric fusions not being a dominant type of chromosome rearrangement in teleosts, it seems that such a mechanism might indeed predominate in some lineages [59]. Within Teleostei, similar patterns of karyotype differentiation as those unraveled in Nannostomus have also been reported for African annual killifish genera Nothobranchius [60] and Chromaphyosemion [61,62], Gobiidae [63], Nothothenoidei [64], ophichthid eels (Ophichthidae) [54], Umbridae [65,66], and, in a broader context, also in the paleopolyploid Salmonidae family, where this process is apparently linked to the re-diploidization processes [67].…”

Section: Discussionmentioning

confidence: 71%

“…As another layer of evidence supporting the significant contribution of fusions in the karyotype dynamics of Nannostomus, the large blocks of constitutive heterochromatin flanking the centromeres of rather large-sized metacentric chromosomes, as found in the karyotypes of N. marginatus and N. unifasciatus, may be potentially considered as relics of two previously independent centromeres linked together by the process of fusion. In fact, such a situation has been repeatedly observed in many teleost species (sometimes, again, accompanied by the presence of rDNA sites in the fusion points) [49][50][51][52][53][54] and it was reported also in other animal taxa, e.g., amphibians [55] or mammals [56,57]. Nonetheless, other studies show that the large pericentromeric heterochromatic blocks can also be found evenly distributed throughout the karyotype regardless of the fusion events (see, e.g., Houck et al [57] and Sousa et al [58]).…”

Section: Discussionmentioning

confidence: 75%

Centric Fusions behind the Karyotype Evolution of Neotropical Nannostomus Pencilfishes (Characiforme, Lebiasinidae): First Insights from a Molecular Cytogenetic Perspective

Sember

Oliveira

Ráb

et al. 2020

Genes

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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 chromosome number (2n), which is pronounced in the speciose genus Nannostomus, a popular taxon in ornamental fish trade due to its remarkable body coloration. Aiming to more deeply examine the karyotype diversification in Nannostomus, we combined conventional cytogenetics (Giemsa-staining and C-banding) with the chromosomal mapping of tandemly repeated 5S and 18S rDNA clusters and with interspecific comparative genomic hybridization (CGH) to investigate genomes of four representative Nannostomus species: N. beckfordi, N. eques, N. marginatus, and N. unifasciatus. Our data showed a remarkable variability in 2n, ranging from 2n = 22 in N. unifasciatus (karyotype composed exclusively of metacentrics/submetacentrics) to 2n = 44 in N. beckfordi (karyotype composed entirely of acrocentrics). On the other hand, patterns of 18S and 5S rDNA distribution in the analyzed karyotypes remained rather conservative, with only two 18S and two to four 5S rDNA sites. In view of the mostly unchanged number of chromosome arms (FN = 44) in all but one species (N. eques; FN = 36), and with respect to the current phylogenetic hypothesis, we propose Robertsonian translocations to be a significant contributor to the karyotype differentiation in (at least herein studied) Nannostomus species. Interspecific comparative genome hybridization (CGH) using whole genomic DNAs mapped against the chromosome background of N. beckfordi found a moderate divergence in the repetitive DNA content among the species’ genomes. Collectively, our data suggest that the karyotype differentiation in Nannostomus has been largely driven by major structural rearrangements, accompanied by only low to moderate dynamics of repetitive DNA at the sub-chromosomal level. Possible mechanisms and factors behind the elevated tolerance to such a rate of karyotype change in Nannostomus are discussed.

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XX/XY sex chromosome system and chromosome markers in the snake eel Ophisurus serpens (Anguilliformes: Ophichtidae)

Cited by 8 publications

References 46 publications

Sex Chromosome Evolution and Genomic Divergence in the Fish Hoplias malabaricus (Characiformes, Erythrinidae)

Sex Chromosome Evolution and Genomic Divergence in the Fish Hoplias malabaricus (Characiformes, Erythrinidae)

GC and Repeats Profiling along Chromosomes—The Future of Fish Compositional Cytogenomics

Centric Fusions behind the Karyotype Evolution of Neotropical Nannostomus Pencilfishes (Characiforme, Lebiasinidae): First Insights from a Molecular Cytogenetic Perspective

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