Molecular Cytogenetics in Digenean Parasites: Linked and Unlinked Major and 5S rDNAs, B Chromosomes and Karyotype Diversification

Digenetic trematodes are the largest group of internal metazoan parasites, but their chromosomes are poorly studied. Although chromosome numbers and/or karyotypes are known for about 300 of the 18,000 described species, molecular cytogenetic knowledge is mostly limited to the mapping of telomeric sequences and/or of major rDNA clusters in 9 species. In this work we mapped major and 5S rDNA clusters and telomeric sequences in chromosomes of Bucephalus minimus, B. australis, Prosorhynchoides carvajali (Bucephaloidea), Monascus filiformis (Gymnophalloidea), Parorchis acanthus (Echinostomatoidea), Cryptocotyle lingua (Opisthorchioidea), Cercaria longicaudata, Monorchis parvus (Monorchioidea), Diphterostomum brusinae, and Bacciger bacciger (Microphalloidea). Whilst single major and minor rDNA clusters were mapped to different chromosome pairs in B. minimus and P. acanthus, overlapping signals were detected on a single chromosome pair in the remaining taxa. FISH experiments using major rDNA and telomeric probes clearly demonstrated the presence of highly stretched NORs in most of the digenean taxa analyzed. B chromosomes were detected in the B. bacciger samples hosted by Ruditapes decussatus. Although the cercariae specimens obtained from Donax trunculus, Tellina tenuis, and R. decussatus were in agreement with B. bacciger, their karyotypes showed striking morphological differences in agreement with the proposed assignation of these cercariae to different species of the genus Bacciger. Results are discussed in comparison with previous data on digenean chromosomes.

Download Full-text

Evolutionary Dynamics of rDNA Clusters in Chromosomes of Five Clam Species Belonging to the Family Veneridae (Mollusca, Bivalvia)

BioMed Research International ◽

10.1155/2014/754012 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9 ◽

Cited By ~ 11

Author(s):

Concepción Pérez-García ◽

Ninoska S. Hurtado ◽

Paloma Morán ◽

Juan J. Pasantes

Keyword(s):

Phylogenetic Trees ◽

Evolutionary Dynamics ◽

5S Rdna ◽

Gene Clusters ◽

Ruditapes Philippinarum ◽

Ruditapes Decussatus ◽

Rdna Cluster ◽

Single Chromosome ◽

Molecular Phylogenetic ◽

Chromosomal Changes

The chromosomal changes accompanying bivalve evolution are an area about which few reports have been published. To improve our understanding on chromosome evolution in Veneridae, ribosomal RNA gene clusters were mapped by fluorescentin situhybridization (FISH) to chromosomes of five species of venerid clams (Venerupis corrugata,Ruditapes philippinarum,Ruditapes decussatus,Dosinia exoleta, andVenus verrucosa). The results were anchored to the most comprehensive molecular phylogenetic tree currently available for Veneridae. While a single major rDNA cluster was found in each of the five species, the number of 5S rDNA clusters showed high interspecies variation. Major rDNA was either subterminal to the short arms or intercalary to the long arms of metacentric or submetacentric chromosomes, whereas minor rDNA signals showed higher variability. Major and minor rDNAs map to different chromosome pairs in all species, but inR. decussatusone of the minor rDNA gene clusters and the major rDNA cluster were located in the same position on a single chromosome pair. This interspersion of both sequences was confirmed by fiber FISH. Telomeric signals appeared at both ends of every chromosome in all species. FISH mapping data are discussed in relation to the molecular phylogenetic trees currently available for Veneridae.

Download Full-text

B Chromosomes and Cytogenetic Characteristics of the Common Nase Chondrostoma nasus (Linnaeus, 1758)

Genes ◽

10.3390/genes11111317 ◽

2020 ◽

Vol 11 (11) ◽

pp. 1317

Author(s):

Alicja Boroń ◽

Anna Grabowska ◽

Aneta Spóz ◽

Anna Przybył

Keyword(s):

Molecular Cytogenetics ◽

5S Rdna ◽

Pericentromeric Region ◽

B Chromosomes ◽

Nucleolar Organizer Regions ◽

Freshwater Species ◽

Chromosomal Distribution ◽

Submetacentric Chromosome ◽

Chondrostoma Nasus ◽

The Common

Supernumerary B chromosomes (Bs) are very promising structures, among others, in that they are an additional genomic compartment for evolution. In this study, we tested the presence and frequency of B chromosomes and performed the first cytogenetic examination of the common nase (Chondrostoma nasus). We investigated the individuals from two populations in the Vistula River basin, in Poland, according to the chromosomal distribution of the C-bands and silver nucleolar organizer regions (Ag-NORs), using sequential staining with AgNO3 and chromomycin A3 (CMA3). Furthermore, we analyzed the chromosomal localization of two rDNA families (45S and 5S rDNA) using fluorescence in situ hybridization (FISH) with rDNA probes. Chondrostoma nasus individuals showed a standard (A) chromosome set consisting of 2n = 50: 12 metacentric, 32 submetacentric, and 6 acrocentric chromosomes (NF = 94). Fourteen out of the 20 analyzed individuals showed 1–2 mitotically unstable submetacentric B chromosomes of different sizes. Six of them, in 14.1% of the analyzed metaphase plates, had a single, medium-sized submetacentric B (Bsm) chromosome (2n = 51) with a heterochromatic block located in its pericentromeric region. The other seven individuals possessed a Bsm (2n = 51) in 19.4% of the analyzed metaphase plates, and a second Bsm chromosome (2n = 52), the smallest in the set, in 15.5% of metaphase plates, whereas one female was characterized by both Bsm chromosomes (2n = 52) in 14.3% of the analyzed metaphase plates. AgNORs, GC-rich DNA sites, and 28S rDNA hybridization sites were observed in the short arms of two submetacentric chromosome pairs of A set. The constitutive heterochromatin was visible as C bands in the centromeric regions of almost all Chondrostoma nasus chromosomes and in the pericentromeric region of several chromosome pairs. Two 5S rDNA hybridization sites in the pericentromeric position of the largest acrocentric chromosome pair were observed, whereas two other such sites in co-localization on a smaller pair of NOR chromosomes indicate a species-specific character. The results herein broaden our knowledge in the field of B chromosome distribution and molecular cytogenetics of Chondrostoma nasus: a freshwater species from the Leuciscidae family.

Download Full-text

B Chromosome Diversity and Repetitive Sequence Distribution in an Isolated Population of Akodon montensis (Rodentia, Sigmodontinae)

Cytogenetic and Genome Research ◽

10.1159/000487471 ◽

2018 ◽

Vol 154 (2) ◽

pp. 79-85

Author(s):

Amanda A. Soares ◽

Jonathan P. Castro ◽

Pedro Balieiro ◽

Sidnei Dornelles ◽

Tiago M. Degrandi ◽

...

Keyword(s):

Evolutionary Dynamics ◽

Repetitive Sequences ◽

5S Rdna ◽

B Chromosome ◽

B Chromosomes ◽

Telomeric Sequences ◽

Supernumerary Chromosomes ◽

Dna Libraries ◽

Eukaryotic Species ◽

Size And Morphology

B chromosomes are supernumerary chromosomes found in the karyotypes of approximately 15% of all eukaryotic species. They present parasitic behavior and do not follow the standard Mendelian pattern of inheritance, resulting in an imbalance in gametogenesis. The evolutionary dynamics of B chromosomes is still unknown for many species, but studies indicate that the accumulation of repetitive sequences plays an important role in the differentiation of these elements. We analyzed morphology, frequency, and possible homologies amongst different B chromosomes found in an isolated Akodon montensis population in southern Brazil. Repetitive sequences (18S, 5S rDNA and telomeric sequences) were used to test for their accumulation on the supernumerary chromosomes and describe their localization in the species. The results indicate 4 different B chromosome morphotypes, and DNA libraries were generated for 3 of them. 18S rDNA was labelled polymorphically, except in the B chromosomes, whereas the 5S rDNA was located exclusively in an interstitial position on the long arm of chromosome 5. Chromosome painting with the B probes based on FISH revealed a homologous composition for all B chromosome morphotypes and no homology with the chromosomes in the A complement. B chromosomes found in this population may have a common origin and subsequently diversified in size and morphology.

Download Full-text

Cytogenetic characterization of the invasive mussel species Xenostrobus securis Lmk. (Bivalvia: Mytilidae)

Genome ◽

10.1139/g11-040 ◽

2011 ◽

Vol 54 (9) ◽

pp. 771-778 ◽

Cited By ~ 14

Author(s):

Concepción Pérez-García ◽

Paloma Morán ◽

Juan J. Pasantes

Keyword(s):

5S Rdna ◽

Gene Clusters ◽

Linker Histone ◽

Histone Gene ◽

Core Histone ◽

Histone Genes ◽

Single Chromosome ◽

Telomeric Sequences ◽

Xenostrobus Securis ◽

Dapi Fluorescence

The chromosomes of the invasive black-pigmy mussel (Xenostrobus securis (Lmk. 1819)) were analyzed by means of 4’,6-diamidino-2-phenylindole (DAPI) / propidium iodide (PI) and chromomycin A3 (CMA) / DAPI fluorescence staining and fluorescent in situ hybridization using major rDNA, 5S rDNA, core histone genes, linker histone genes, and telomeric sequences as probes. The diploid chromosome number in this species is 2n = 30. The karyotype is composed of seven metacentric, one meta/submetacentric, and seven submetacentric chromosome pairs. Telomeric sequences appear at both ends of every single chromosome. Major rDNA clusters appear near the centromeres on chromosome pairs 1 and 3 and are associated with bright CMA fluorescence and dull DAPI fluorescence. This species shows five 5S rDNA clusters close to the centromeres on four chromosome pairs (2, 5, 6, and 8). Three of the four core histone gene clusters map to centromeric positions on chromosome pairs 7, 10, and 13. The fourth core histone gene cluster occupies a terminal position on chromosome pair 8, also bearing a 5S rDNA cluster. The two linker histone gene clusters are close to the centromeres on chromosome pairs 12 and 14. Therefore, the use of these probes allows the unequivocal identification of 11 of the 15 chromosome pairs that compose the karyotype of X. securis.

Download Full-text

Chromosome Painting in Trogon s. surrucura (Aves, Trogoniformes) Reveals a Karyotype Derived by Chromosomal Fissions, Fusions, and Inversions

Cytogenetic and Genome Research ◽

10.1159/000471782 ◽

2017 ◽

Vol 151 (4) ◽

pp. 208-215 ◽

Cited By ~ 11

Author(s):

Tiago M. Degrandi ◽

Analía del Valle Garnero ◽

Patricia C.M. O'Brien ◽

Malcolm A. Ferguson-Smith ◽

Rafael Kretschmer ◽

...

Keyword(s):

Chromosome Painting ◽

Molecular Cytogenetics ◽

Molecular Data ◽

Wide Distribution ◽

Forest Birds ◽

Chicken Chromosome ◽

Chromosome 1Q ◽

Phylogenetic Studies ◽

Morphological Differences ◽

Paracentric Inversions

Trogons are forest birds with a wide distribution, being found in Africa, Asia, and America, and are included in the order Trogoniformes, family Trogonidae. Phylogenetic studies using molecular data have not been able to determine the phylogenetic relationship among the different genera of trogons. So far, no cytogenetic data for these birds exist. Hence, the aim of this study was to characterize the karyotype of Trogon surrucura surrucura by means of classical and molecular cytogenetics. We found a diploid chromosome number of 2n = 82, similar to most birds, with several derived features compared to chicken and the putative ancestral avian karyotype. T. s. surrucura showed 3 pairs of microchromosomes bearing 18S rDNA clusters. The Z and W sex chromosomes were of similar size but could readily be identified by morphological differences. Using chromosome painting with whole chromosome probes from Gallus gallus and Leucopternis albicollis, we found that the chromosomes homologous to chicken chromosomes 2 and 5 correspond to 2 different pairs in T. s. surrucura and L. albicollis, due to the occurrence of centric fissions. Paracentric inversions were detected in the segment homologous to chicken chromosome 1q, and we confirmed the recurrence of breakpoints when our results were compared to other species of birds already analyzed by FISH or by in silico genome assembly.

Download Full-text

Sex Chromosomes and Internal Telomeric Sequences in Dormitator latifrons (Richardson 1844) (Eleotridae: Eleotrinae): An Insight into Their Origin in the Genus

Genes ◽

10.3390/genes11060659 ◽

2020 ◽

Vol 11 (6) ◽

pp. 659

Author(s):

Fabilene Gomes Paim ◽

Mauro Nirchio ◽

Claudio Oliveira ◽

Anna Rita Rossi

Keyword(s):

Sex Chromosomes ◽

Food Resource ◽

5S Rdna ◽

Molecular Techniques ◽

Chromosomal Mapping ◽

Nucleolar Organizer Regions ◽

Neotropical Fish ◽

Telomeric Repeats ◽

Western Atlantic ◽

Telomeric Sequences

The freshwater fish species Dormitator latifrons, commonly named the Pacific fat sleeper, is an important food resource in CentralSouth America, yet almost no genetic information on it is available. A cytogenetic analysis of this species was undertaken by standard and molecular techniques (chromosomal mapping of 18S rDNA, 5S rDNA, and telomeric repeats), aiming to describe the karyotype features, verify the presence of sex chromosomes described in congeneric species, and make inferences on chromosome evolution in the genus. The karyotype (2n = 46) is mainly composed of metacentric and submetacentic chromosomes, with nucleolar organizer regions (NORs) localized on the short arms of submetacentric pair 10. The presence of XX/XY sex chromosomes was observed, with the X chromosome carrying the 5S rDNA sequences. These heterochromosomes likely appeared before 1 million years ago, since they are shared with another derived Dormitator species (Dormitator maculatus) distributed in the Western Atlantic. Telomeric repeats hybridize to the terminal portions of almost all chromosomes; additional interstitial sites are present in the centromeric region, suggesting pericentromeric inversions as the main rearrangement mechanisms that has driven karyotypic evolution in the genus. The data provided here contribute to improving the cytogenetics knowledge of D. latifrons, offering basic information that could be useful in aquaculture farming of this neotropical fish.

Download Full-text

Insights into Emydid Turtle Cytogenetics: The European Pond Turtle as a Model Species

Cytogenetic and Genome Research ◽

10.1159/000495833 ◽

2019 ◽

Vol 157 (3) ◽

pp. 166-171 ◽

Cited By ~ 3

Author(s):

Alessio Iannucci ◽

Marta Svartman ◽

Massimo Bellavita ◽

Guido Chelazzi ◽

Roscoe Stanyon ◽

...

Keyword(s):

Chromosome Banding ◽

Molecular Cytogenetics ◽

Comparative Genomic ◽

Emys Orbicularis ◽

Rdna Genes ◽

Telomeric Sequences ◽

Pond Turtle ◽

Cytogenetic Data ◽

Cryptic Sex

Our knowledge of Testudines evolution is limited by the lack of modern cytogenetic data. Compared to other reptiles, there is little information even on chromosome banding, let alone molecular cytogenetic data. Here, we provide detailed information on the karyotype of the European pond turtle Emys orbicularis, a model Emydidae, employing both chromosome banding and molecular cytogenetics. We provide a high-resolution G-banded karyotype and a map of rDNA genes and telomeric sequences using fluorescence in situ hybridization. We test hypotheses of sex-determining mechanisms in Emys by comparative genomic hybridization to determine if Emys has a cryptic sex-specific region. Our results provide valuable data to guide future efforts on genome sequencing and anchoring in Emydidae and for understanding karyotype evolution in Testudines.

Download Full-text

Two new species of Acanthocotyle Monticelli, 1888 (Monogenea: Acanthocotylidae), parasites of two deep-sea skates (Elasmobranchii: Rajiformes) in the South-East Pacific

Parasites & Vectors ◽

10.1186/s13071-019-3756-5 ◽

2019 ◽

Vol 12 (1) ◽

Cited By ~ 1

Author(s):

Luis A. Ñacari ◽

Fabiola A. Sepúlveda ◽

Ruben Escribano ◽

Marcelo E. Oliva

Keyword(s):

New Species ◽

Deep Sea ◽

The South ◽

Metazoan Parasites ◽

Closely Related Species ◽

Deep Waters ◽

East Pacific ◽

Two New Species ◽

Morphological Differences ◽

By Catch

Abstract Background Parasites of deep-sea fishes from the South-East Pacific (SPO) are poorly known. Of c.1030 species of fish found in this area, 100–150 inhabit the deep-sea (deeper than 200 m). Only six articles concerning metazoan parasites of fish from deep-waters of SOP are known, and nine monogenean species have been reported. Currently, ten species are known in Acanthocotyle Monticelli, 1888 (Monogenea) and when stated, all of them are found in shallow waters (10–100 m). Acanthocotyle gurgesiella Ñacari, Sepulveda, Escribano & Oliva, 2018 is the only known species parasitizing deep-sea skates (350–450 m) in the SPO. The aim of this study was the description of two new species of Acanthocotyle from two Rajiformes. Methods In September 2017, we examined specimens of two species of deep-sea skates (Rajiformes), Amblyraja frerichsi (Krefft) and Bathyraja peruana McEachran & Myyake, caught at c.1500 m depth off Tocopilla, northern Chile, as a by-catch of the Patagonian tooth fish Dissostichus eleginoides Smitt fishery. Specimens of Acanthocotyle were collected from the skin of the skates. Morphometric (including multivariate analysis of proportional measurements, standardized by total length), morphological and molecular analyses (LSU rRNA and cox1 genes) were performed in order to identify the collected specimens. Results The three approaches used in this study strongly suggest the presence of two new species in the genus Acanthocotyle: Acanthocotyle imo n. sp. and Acanthocotyle atacamensis n. sp. parasitizing the skin of the thickbody skate Amblyraja frerichsi and the Peruvian skate Bathyraja peruana, respectively. The main morphological differences from the closely related species Acanthocotyle verrilli Goto, 1899 include the number of radial rows of sclerites, the non-discrete vitelline follicles and the number of testes. Conclusions The two species of monogeneans described here are the only recorded parasites from their respective host species in the SPO. Assessing host specificity for members of Acanthocotyle requires clarifying the systematics of Rajiformes.

Download Full-text

Evolution of Bird Sex Chromosomes Narrated by Repetitive Sequences: Unusual W Chromosome Enlargement in Gallinula melanops (Aves: Gruiformes: Rallidae)

Cytogenetic and Genome Research ◽

10.1159/000501381 ◽

2019 ◽

Vol 158 (3) ◽

pp. 152-159 ◽

Cited By ~ 5

Author(s):

Ricardo J. Gunski ◽

Rafael Kretschmer ◽

Marcelo Santos de Souza ◽

Ivanete de Oliveira Furo ◽

Suziane A. Barcellos ◽

...

Keyword(s):

Sex Chromosomes ◽

18S Rdna ◽

Organizer Region ◽

Repetitive Sequences ◽

Nucleolar Organizer Region ◽

Molecular Cytogenetics ◽

5S Rdna ◽

Nucleolar Organizer ◽

W Chromosome ◽

Rdna Sites

Among birds, species with the ZZ/ZW sex determination system generally show significant differences in morphology and size between the Z and W chromosomes (with the W usually being smaller than the Z). In the present study, we report for the first time the karyotype of the spot-flanked gallinule (Gallinula melanops) by means of classical and molecular cytogenetics. The spot-flanked gallinule has 2n = 80 (11 pairs of macrochromosomes and 29 pairs of microchromosomes) with an unusual W chromosome that is larger than the Z. Besides being totally heterochromatic, it has a secondary constriction in its long arm corresponding to the nucleolar organizer region, as confirmed by both silver staining and mapping of 18S rDNA probes. This is an unprecedented fact among birds. Additionally, 18S rDNA sites were also observed in 6 microchromosomes, while 5S rDNA was found in just 1 microchromosomal pair. Seven out of the 11 used microsatellite sequences were found to be accumulated in microchromosomes, and 6 microsatellite sequences were found in the W chromosome. In addition to the involvement of heterochromatin and repetitive DNAs in the differentiation of the large W chromosome, the results also show an alternative scenario that highlights the plasticity that shapes the evolutionary history of bird sex chromosomes.

Download Full-text

Cytogenetic analysis of Baryancistrus xanthellus (Siluriformes: Loricariidae: Ancistrini), an ornamental fish endemic to the Xingu River, Brazil

Neotropical Ichthyology ◽

10.1590/1982-0224-20150108 ◽

2016 ◽

Vol 14 (2) ◽

Cited By ~ 3

Author(s):

Larissa A. Medeiros ◽

Eduardo G. Ginani ◽

Leandro M. Sousa ◽

Lúcia H. Rapp Py-Daniel ◽

Eliana Feldberg

Keyword(s):

Organizer Region ◽

Nucleolus Organizer Region ◽

5S Rdna ◽

Color Pattern ◽

Nucleolus Organizer ◽

Interstitial Position ◽

Single Chromosome ◽

Xingu River ◽

Belo Monte ◽

Basal Position

ABSTRACT Baryancistrus xanthellus is a species from the Ancistrini tribe known commonly as "amarelinho " or "golden nugget pleco". It is one of the most popular and valued ornamental fishes due to its color pattern. Also, it is an endemic species from the Xingu River occurring from Volta Grande do Xingu, region where the Belo Monte Hydropower Dam is being built, to São Félix do Xingu. The current study aimed to cytogenetically characterize B. xanthellus . Results point to the maintenance of 2n=52, which is considered the most common condition for the tribe, and a single nucleolus organizer region (NOR). Mapping of the 18S rDNA confirmed the NOR sites, and the 5S rDNA was mapped in the interstitial position of a single chromosome pair. The 18S and 5S rDNA located in different pairs constitute an apomorphy in Loricariidae. Large blocks of heterochromatin are present in pairs 1 and 10 and in the regions equivalent to NOR and the 5S rDNA. Data obtained in this study corroborated with the currently accepted phylogenetic hypothesis for the Ancistrini and demonstrate evidence that the genus Baryancistrus occupies a basal position in the tribe.

Download Full-text