7 research outputs found

    5S ribosomal RNA genes in six species of Mediterranean grey mullets: Genomic organization and phylogenetic inference

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    This paper describes a study of the 5S ribosomal RNA genes (5S rDNA) in a group of 6 species belonging to 4 genera of Mugilidae. In these 6 species, the relatively short 5S rDNA repeat units, generated by PCR and ranging in size from 219 to 257 bp, show a high level of intragenomic homogeneity of both coding and spacer regions (NTS-I). Phylogenetic reconstructions based on this data set highlight the greater phylogenetic and genetic diversity of Mugil cephalus and Oedalechilus labeo compared with the genera Liza and Chelon. Comparative sequence analysis revealed significant conservation of the short 5S rDNA repeat units across Chelon and Liza. Moreover, a second size class of 5S rDNA repeat units, ranging from roughly 800 to 1100 bp, was produced in the Liza and Chelon samples. Only short 5S rDNA repeat units were found in M. cephalus and O. labeo. The sequences of the long 5S rDNA repeat units, obtained in Chelon labrosus and Liza ramada, differ owing to the presence of 2 large insertion/deletions (indels) in the spacers (NTS-II) and show considerable sequence identity with NTS-I spacers. Interspecific sequence variation of NTS-II spacers, excluding the indels, is low. Southern-blot hybridization patterns suggest an intermixed arrangement of short and long repeat units within a single chromosome locus. © 2007 NRC

    The first cytogenetic description of Euleptes europaea (Gené, 1839) from Northern Sardinia reveals the highest diploid chromosome number among sphaerodactylid geckos (Sphaerodactylidae, Squamata)

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    The karyotype of a sphaerodactylid gecko Euleptes europaea (Gené, 1839) was assembled for the first time in this species. It is made of 2n = 42 gradually decreasing in size chromosomes, the highest chromosome number so far acknowledged in the family Sphaerodactylidae. The second chromosome pair of the karyotype appears slightly heteromorphic in the male individual. Accordingly, FISH with a telomeric probe revealed an uneven distribution of telomeric repeats on the two homologues of this pair, which may be indicative of an XY sex-determination system in the species, to be further investigated

    Comparative cytogenetic and genetic study of two Italian populations of the garden dormouse Eliomys quercinus L. (Sciuromorpha: Gliridae)

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    The garden dormouse Eliomys quercinus is a polytypic species that shows remarkable chromosomal variation (2n = 48, 50, 52, 54). Furthermore, among 2n = 48 populations of the species, distributed mainly in the circum-Mediterranean area, different populations may exhibit distinctive karyotypes. Here we analyse samples of E. quercinus from Sicily, the insular population so far barely studied, compared to the samples from the Central Apennines. The two populations show the same cytotype (2n = 48, NFa = 86), matching G- and C- chromosome banding patterns, and identical chromosome locations of major ribosomal genes (rDNA) and interstitial telomeric sequences (ITS). The samples from the two Italian populations show low genetic divergence (1.2%) based on mitochondrial cytochrome b gene sequence analysis, which suggests that both populations belong to the same taxon - E. quercinus pallidus. In addition, we compare the present results to karyological data reported in other 2n = 48 populations and identify possible chromosomal rearrangements

    Comparative cytogenetics of moles (Eulipotyphla, Talpidae): Chromosomal differences in Talpa romana and T. europaea

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    The genus Talpa is the most specious and widespread one in the family Talpidae. The existing karyological records are predominantly basic morphological descriptions. To further investigate the case in point, we performed a comparative cytogenetic study in the genus by comparing G- and C-chromosome banding and NOR patterns of the two European species, T. romana and T. europaea, along with available data regarding several other mole species. Chromosomal hybridization patterns for telomeric repeats and major and 5S ribosomal RNA genes were obtained in T. romana and T. europaea for the first time. The comparison of these patterns revealed differences in distribution of interstitial telomeric repeats and 5S ribosomal RNA genes in the two species with apparently identical karyotypes but different evolutionary histories. Copyright © 2008 S. Karger AG

    Pattern of chromosomal changes in 'beta' Anolis (Norops group) (Squamata: Polychrotidae) depicted by an ancestral state analysis

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    Background: Neotropical lizards, genus Anolis (Polychrotidae), with nearly 380 species, are members of one of the most diversified genera among amniotes. Herein, we present an overview of chromosomal evolution in 'beta' Anolis (Norops group) as a baseline for future studies of the karyotypic evolution of anoles. We evaluated all available information concerning karyotypes of Norops, including original data on a recently described species, Anolis unilobatus. We used the phylogeny of Norops based on DNA sequence data to infer the main pattern of chromosomal evolution by means of an ancestral state analysis (ASR). Results: We identified 11 different karyotypes, of which 9 in the species had so far been used in molecular studies. The ASR indicated that a change in the number of microchromosomes was the first evolutionary step, followed by an increase in chromosome numbers, likely due to centric fissions of macrochromosomes. The ASR also showed that in nine species, heteromorphic sex chromosomes most probably originated from six independent events. Conclusions: We observed an overall good correspondence of some characteristics of karyotypes and species relationships. Moreover, the clade seems prone to sex chromosome diversification, and the origins of five of these heteromorphic sex chromosome variants seem to be recent as they appear at the tip nodes in the ancestral character reconstruction. Karyotypic diversification in Norops provides an opportunity to test the chromosomal speciation models and is expected to be useful in studying relationships among anole species and in identifying cryptic taxa

    Karyotypic diversification due to Robertsonian rearrangements in Phyllodactylus lanei Smith, 1935 (Squamata, Gekkonidae) from Mexico

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    We analyzed chromosomes of male and female individuals of Phyllodactylus lanei Smith, 1935 (Squamata, Gekkonidae) from Chamela-Cuixmala Biosphere Reserve, Jalisco state, Mexico. The karyotype constructed for these specimens is composed of 19 pairs of telocentric chromosomes (2n = 38, FN = 38). This karyotype, due to Robertsonian fusions/fissions, differs from the one previously reported in samples from the State of Guerrero, which probably belonged to a different subspecies (2n = 33-34, FN = 40-41). Moreover, a presumed ZW sex chromosome system was not confirmed in the presently studied individuals

    Comparative cytogenetics of two species of ground skinks: Scincella assata and S. cherriei (Squamata: Scincidae: Lygosominae) from Chiapas, Mexico

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    Standard karyotypes of two species of the genus Scincella, S. assata and S. cherriei, both from Chiapas State, Mexico, were described for the first time. The diploid chromosome number was 28 in S. assata, whereas 30 in S. cherriei. The karyotypes of the two species, while differing in the number of microchromosomes, 14-15 in S. assata and 16-17 in S. cherriei, share four pairs of large metacentric, two pairs of medium-sized metacentric, and one particular pair (number 7) of chromosomes. Female S. assata carries chromosome pair 7 composed of two identical mediumsized subtelocentric chromosomes. This chromosome pair is heteromorphic in males of both species, i.e., one component of the pair is similar to the homomorphic chromosomes 7 of the S. assata female, while the other is nearly one-half the size of its counterpart and resembles a microchromosome. The homology of such externally different elements is deducted from the presence of an asymmetric bivalent in spermatocytes at diplotene-diakinesis. Female S. cherriei was not available. We suspect that the two Scincella species possess an XY sex determination system, as previously reported for the North American congeneric species, S. lateralis. © Firenze University Press
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