Latest Articles from Comparative Cytogenetics Latest 4 Articles from Comparative Cytogenetics https://compcytogen.pensoft.net/ Thu, 28 Mar 2024 21:18:07 +0200 Pensoft FeedCreator https://compcytogen.pensoft.net/i/logo.jpg Latest Articles from Comparative Cytogenetics https://compcytogen.pensoft.net/ Karyotype differentiation in the Nothobranchius ugandensis species group (Teleostei, Cyprinodontiformes), seasonal fishes from the east African inland plateau, in the context of phylogeny and biogeography https://compcytogen.pensoft.net/article/97165/ Comparative Cytogenetics 17: 13-29

DOI: 10.3897/compcytogen.v7.i1.97165

Authors: Eugene Yu. Krysanov, Béla Nagy, Brian R. Watters, Alexandr Sember, Sergey A. Simanovsky

Abstract: The karyotype differentiation of the twelve known members of the Nothobranchius ugandensis Wildekamp, 1994 species group is reviewed and the karyotype composition of seven of its species is described herein for the first time using a conventional cytogenetic protocol. Changes in the architecture of eukaryotic genomes often have a major impact on processes underlying reproductive isolation, adaptation and diversification. African annual killifishes of the genus Nothobranchius Peters, 1868 (Teleostei: Nothobranchiidae), which are adapted to an extreme environment of ephemeral wetland pools in African savannahs, feature extensive karyotype evolution in small, isolated populations and thus are suitable models for studying the interplay between karyotype change and species evolution. The present investigation reveals a highly conserved diploid chromosome number (2n = 36) but a variable number of chromosomal arms (46–64) among members of the N. ugandensis species group, implying a significant role of pericentric inversions and/or other types of centromeric shift in the karyotype evolution of the group. When superimposed onto a phylogenetic tree based on molecular analyses of two mitochondrial genes the cytogenetic characteristics did not show any correlation with the phylogenetic relationships within the lineage. While karyotypes of many other Nothobranchius spp. studied to date diversified mainly via chromosome fusions and fissions, the N. ugandensis species group maintains stable 2n and the karyotype differentiation seems to be constrained to intrachromosomal rearrangements. Possible reasons for this difference in the trajectory of karyotype differentiation are discussed. While genetic drift seems to be a major factor in the fixation of chromosome rearrangements in Nothobranchius, future studies are needed to assess the impact of predicted multiple inversions on the genome evolution and species diversification within the N. ugandensis species group.

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Research Article Tue, 31 Jan 2023 18:54:24 +0200
Extensive karyotype variability of African fish genus Nothobranchius (Cyprinodontiformes) https://compcytogen.pensoft.net/article/25092/ Comparative Cytogenetics 12(3): 387-402

DOI: 10.3897/CompCytogen.v12i3.25092

Authors: Eugene Krysanov, Tatiana Demidova

Abstract: Karyotypes of 65 species of the genus Nothobranchius Peters, 1868 were reviewed and of those 35 examined first time. The results of present study have shown that fishes of the genus Nothobranchius possessed highly diverse karyotypes. The diploid chromosome number (2n) ranged from 16 to 50. The most frequent 2n was 2n = 36 (in 35 species) while the second one 2n = 38 (in 13 species). Proportion of biarmed chromosomes varied from 0 to 95% between species. Diploid chromosome number variability apparently exists as a result of chromosomal fusions or fissions and extensive karyotypic formula alterations promoting by inversions. Multiple sex chromosomes of system X1X1X2X2/X1X2Y type were found only in karyotypes of 5 species. The extensive karyotype variability, unusual for teleosts, of genus Nothobranchius can be likely associated with the characteristics of its life cycle and inhabiting under unstable environment of East African savannah temporal pools.

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Research Article Mon, 10 Sep 2018 18:14:23 +0300
Chromosomal organization of four classes of repetitive DNA sequences in killifish Orestias ascotanensis Parenti, 1984 (Cyprinodontiformes, Cyprinodontidae) https://compcytogen.pensoft.net/article/11729/ Comparative Cytogenetics 11(3): 463-475

DOI: 10.3897/compcytogen.v11i3.11729

Authors: Cristian Araya-Jaime, Natalia Lam, Irma Vila Pinto, Marco A. Méndez, Patricia Iturra

Abstract: Orestias Valenciennes, 1839 is a genus of freshwater fish endemic to the South American Altiplano. Cytogenetic studies of these species have focused on conventional karyotyping. The aim of this study was to use classical and molecular cytogenetic methods to identify the constitutive heterochromatin distribution and chromosome organization of four classes of repetitive DNA sequences (histone H3 DNA, U2 snRNA, 18S rDNA and 5S rDNA) in the chromosomes of O. ascotanensis Parenti, 1984, an endemic species restricted to the Salar de Ascotán in the Chilean Altiplano. All individuals analyzed had a diploid number of 48 chromosomes. C-banding identified constitutive heterochromatin mainly in the pericentromeric region of most chromosomes, especially a GC-rich heterochromatic block of the short arm of pair 3. FISH assay with an 18S probe confirmed the location of the NOR in pair 3 and revealed that the minor rDNA cluster occurs interstitially on the long arm of pair 2. Dual FISH identified a single block of U2 snDNA sequences in the pericentromeric regions of a subtelocentric chromosome pair, while histone H3 sites were observed as small signals scattered in throughout the all chromosomes. This work represents the first effort to document the physical organization of the repetitive fraction of the Orestias genome. These data will improve our understanding of the chromosomal evolution of a genus facing serious conservation problems.

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Research Article Tue, 25 Jul 2017 11:38:05 +0300
Divergent karyotypes of the annual killifish genus Nothobranchius (Cyprinodontiformes, Nothobranchiidae) https://compcytogen.pensoft.net/article/9863/ Comparative Cytogenetics 10(3): 439-445

DOI: 10.3897/CompCytogen.v10i3.9863

Authors: Eugene Krysanov, Tatiana Demidova, Bela Nagy

Abstract: Karyotypes of two species of the African annual killifish genus Nothobranchius Peters, 1868, N. brieni Poll, 1938 and Nothobranchius sp. from Kasenga (D.R. Congo) are described. Both species displayed diploid chromosome number 2n = 49/50 for males and females respectively with multiple-sex chromosome system type X1X2Y/X1X1X2X2. The karyotypes of studied species are considerably different from those previously reported for the genus Nothobranchius and similar to the Actinopterygii conservative karyotype.

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Short Communication Fri, 16 Sep 2016 20:42:02 +0300