Chromosomal banding in three species of the genus Rineloricaria (Siluriformes, Loricariidae, Loricariinae)

Cytogenetic analyses were conducted in three species: Rineloricaria cadeae, Rineloricaria strigilata and Rineloricaria pentamaculata. The nucleolar organizing regions (NORs) were localized at the terminal position, on the ninth pair of the complement for R. cadeae and R. strigilata, on the eighth and sixth pair of st–a, respectively; and on the fifth pair of the complement for R. pentamaculata, the first pair of st–a. Rineloricaria strigilata and R. pentamaculata showed NOR heteromorphism and polymorphism, respectively. All species showed heterochromatin in the pericentromeric regions and associated with NORs, which were chromomycin A₃ (CMA₃) positive, demonstrating to be GC rich. The results show that NOR is nonconservative in this genus.     

Cytogenetic study in Corydoras britskii (Siluriformes: Callichthyidae), using different chromosomal banding and fluorescence hybridization in situ with rDNA probes

Cytogenetic analyses were performed on Corydoras britskii from the Miranda River basin, an important river located in the Pantanal, Mato Grosso do Sul State, Brazil. The karyotype of this species comprises 90 chromosomes and a karyotype formula of 4m + 10 sm + 22 st + 54a. The nucleolus organizer regions were detected by impregnation with silver nitrate and FISH with an 18S rDNA probe on the short arm of three acrocentric chromosomes. The constitutive heterochromatin is distributed in pericentromeric and interstitial positions, and also associated with the NORs. The HinfI restriction endonuclease was used and showed homology with practically all types of heterochromatin observed in C. britskii, except for two interstitial heterochromatic blocks present in a subtelocentric pair. The fluorochrome staining evidenced six chromosomes with chromomycin-positive signals indicating that both the heterochromatin interspersed with NORs and some heterochromatic blocks were rich in GC base pairs. FISH using a 5S rDNA probe revealed the presence of these regions in only one subtelocentric pair in the interstitial position. The obtained data substantiate the karyotype diversity of the genus Corydoras and provide novel information about the composition of heterochromatin and location of 5S and 18S rDNA sites.     

Cytogenetic characterization of the ant Trachymyrmex fuscus Emery, 1934 (Formicidae: Myrmicinae: Attini) with the description of a chromosomal polymorphism

The genus Trachymyrmex is a key group in the tribe Attini because of its close phylogenetic relationship to leaf-cutter ants, Acromyrmex and Atta. Cytogenetic data are only available for five taxa of Trachymyrmex, with chromosome numbers of 2n = 12, 18, 20 and 22, and morphology with predominantly metacentric chromosomes. The aim of the present study was to characterize the karyotype of the ant Trachymyrmex fuscus Emery, 1934, by means of the number and morphology of its chromosomes, heterochromatin pattern, CMA₃ and DAPI fluorochromes in the population of two nests collected at Paraopeba, state of Minas Gerais, Brazil. Nineteen females presented 2n = 18 chromosomes (16m + 2sm) and a single male presented n = 9 (8m + 1sm). A size chromosomal polymorphism involving the short arm of the submetacentric pair was confirmed by statistical analysis, with three character conditions: heterozygous SB (with a difference in size between the short arms), standard SS (smaller short arms) and homozygote BB (bigger short arms). In the first nest, both SB and SS workers were observed. The other nest contained heterozygous (SB), homozygous (BB), and a male carrying the B chromosome (larger size). The presence of heterochromatin on all centromeric and pericentromeric chromosomes of T. fuscus suggests that the size difference observed in the submetacentric pair in the SB and BB workers is not related to the heterochromatin but to a duplication of euchromatic regions through intra- or inter- chromosomal rearrangements. The fluorochrome CMA₃ matched the C-banding markings, indicating that the heterochromatin is rich in GC base pairs. As far as we know, this is the first chromosomal polymorphism reported in the tribe Attini.     

Cytogenetics of Alismatales s.s.: chromosomal evolution and C-banding

Ten species of Alismatales, five of Alismataceae, four of Limnocharitaceae and one of Hydrocharitaceae were studied with regard to chromosome number, chromosome morphology, and pattern of Giemsa C-bands. The genus Echinodorus had a diploid chromosome number of 22 for all species that were analyzed and a karyotypic formula of 2m + 20a. For the family Limnocharitaceae, Hydrocleys nymphoides had a diploid chromosome number of 16, Hydrocleys martii (4m + 2sm + 10a) had a diploid chromosome number of 16, Limnocharis flava had a diploid chromosome number of 20 and L. laforestii (4m + 16a) had a diploid chromosome number of 20. The only species of Hydrocharitaceae that was studied exhibited a karyotype that consisted of a diploid chromosome number of 28 and a karyotypic formula of 4m + 6sm + 4a. The distribution pattern of the C-banded karyotype in Echinodorus showed four blocks of constitutive heterochromatin in two smaller acrocentric pairs that corresponded to the heterochromatic NORs. In E. lanceolatus, 14 bands in the termini of the arms beyond the heterochromatic NORs of seven acrocentric pairs were also observed. Idiograms are presented and the karyotypic evolution patterns for the studied groups are discussed.     

XX/XO, a rare sex chromosome system in Potamotrygon freshwater stingray from the Amazon Basin, Brazil

Potamotrygonidae is a representative family of South American freshwater elasmobranchs. Cytogenetic studies were performed in a Potamotrygon species from the middle Negro River, Amazonas, Brazil, here named as Potamotrygon sp. C. Mitotic and meiotic chromosomes were analyzed using conventional staining techniques, C-banding, and detection of the nucleolus organizing regions (NOR) with Silver nitrate (Ag-NOR). The diploid number was distinct between sexes, with males having 2n = 67 chromosomes, karyotype formula 19m + 8sm + 10st + 30a, and fundamental number (FN) = 104, and females having 2n = 68 chromosomes, karyotype formula 20m + 8sm + 10st + 30a, and FN = 106. A large chromosome, corresponding to pair number two in the female karyotype, was missing in the male complement. Male meiotic cells had 33 bivalents plus a large univalent chromosome in metaphase I, and n = 33 and n = 34 chromosomes in metaphase II. These characteristics are consistent with a sex chromosome system of the XX/XO type. Several Ag-NOR sites were identified in both male and female karyotypes. Positive C-banding was located only in the centromeric regions of the chromosomes. This sex chromosome system, which rarely occurs in fish, is now being described for the first time among the freshwater rays of the Amazon basin.     

Atlantic moonfishes: independent pathways of karyotypic and morphological differentiation

Fish of the genus Selene, known as lookdowns or moonfish, are one of the most morphologically derived groups of the family Carangidae, whose phylogenetic relationships are still largely unknown. In this study, we discuss karyoevolutionary aspects of three representatives of this genus from the Western Atlantic: Selene brownii (2n = 48; FN = 48), Selene setapinnis (2n = 46; FN = 48), and Selene vomer (2n = 48; FN = 50). Their body patterns were also investigated and compared to one another and in relation to two other species of different genera. Two mechanisms of karyotypic evolution seem to have acted in the diversification of this genus, namely pericentric inversions and centric fusions. Mapping of rDNA sequences showed that chromosome pairs bearing 5S rDNA sites are similar, whereas those bearing 18 rDNA sites are morphologically distinct while apparently also exhibiting interspecies synteny. Although the nucleolar organizer-bearing chromosomes are extremely efficient cytotaxonomic markers among Selene species, others cytogenetic patterns of these species are relatively conserved. Hybridization with telomeric probes (TTAGGG)_n did not exhibit interstitial telomeric sites (ITS), especially in S. setapinnis, where, along with a reduction in diploid number, a large metacentric pair derived from centric fusion is present. Data obtained by geometric morphometrics enable a clear morphological distinction among the three species, as well as in relation to two other species of the genus Caranx and Oligoplites. Data obtained suggest that morphologic evolution in Selene species was primarily dissociated from visible changes that occurred at the chromosomal level.     

Classical and molecular cytogenetics and DNA content in Maihuenia and Pereskia (Cactaceae)

We studied cacti species of the subfamilies Pereskioideae (five species of the southern clade) and both species of Maihuenioideae using molecular cytogenetic techniques and DNA content. Mitotic chromosomes were analyzed for Pereskia aculeata, P. bahiensis, P. grandifolia, P. nemorosa, P. sacharosa, Maihuenia poeppigii, and M. patagonica, using the Feulgen stain, CMA/DAPI fluorescent chromosome banding, fluorescence in situ hybridization (FISH, probes of 5S rDNA and pTa71 for 18-5.8-26S rDNA), and DNA content by flow cytometry technique. The karyotypes were highly symmetrical, most of the pairs being metacentric (m). CMA/DAPI banding revealed the presence of CMA⁺/DAPI^? bands associated with NORs in the first m pair of all species. The co-localization of 18-5.8-26S rDNA loci with CMA⁺/DAPI^?/NORs blocks allowed the identification of homeologous chromosome pairs between species of both subfamilies. FISH using probe 5S rDNA was applied for the first time in both subfamilies. Diploid species had always one m pair carrying 5S rDNA genes, with pericentromeric location in different chromosome pairs. In the tetraploid cytotype of M. patagonica, the 5S rDNA probe hybridized to two pairs. The 2C DNA content obtained by FC varied twofold (from 1.85 to 2.52 pg), with significant differences between species. Mean chromosome length, karyotype formula, percentage of heterochromatin position of 5S rDNA locus, and nuclear Cx DNA content vary among Maihuenia and Pereskia species and allowed to differentiate them. Both genera are closely related and that the differences found are not strong enough to separate Maihuenioideae from Pereskioideae.     

Karyological features and banding patterns in Arachis species belonging to the Heteranthae section

The section Heteranthae of Arachis is endemic to Brazil, occurring mainly in the semi-arid northeastern region. The section is considered derived within the genus and includes only annual herbs. Most previous cytological evaluations were restricted to chromosome numbers and morphology. The present approach comprised karyomorphological evaluation in 10 accessions from five species of this section, including standard staining and fluorochrome banding [chromomycin A3 (CMA)/4′,6-diamidino-2-phenylindole (DAPI)]. All accessions presented diploid chromosome numbers (2n = 20) with a prevalence of metacentric to submetacentric chromosome morphology. Arachis dardani, Arachis pusilla, and Arachis interrupta presented karyotypic formula 18m + 4sm and satellite type 2, while Arachis sylvestris and Arachis giacomettii presented 16m + 4sm and satellite type 10. Despite the conserved morphological features, higher diversity was detected in terms of size and number of GC-rich (CMA⁺) heterochromatic blocks among the species; however, all of them were located in the pericentromeric regions. The species A. pusilla presented the highest number of GC-rich blocks, present in all chromosomes of the complement. Based on the data obtained and considering literature data, we suggest that A. dardani and A. interrupta occupy a basal position in the group due to their moderate asymmetry and satellite type. At least in A. pusilla, the constitutive heterochromatin seems to have suffered recent modifications of its constitution, in contrast to other species that present pericentromeric CMA⁺ blocks in all chromosomes. A. giacomettii and A. sylvestris are closely related to each other and also similar to the previously studied Arachis seridoensis, revealing two clear-cut subgroups within the section from the karyological point of view.     

Karyotype analysis for diploid and polyploid species of the Solanum L.

Solanum species were cytogenetically analysed to localize species-specific markers. Solanum atropurpureum Schrank, S. dulcamara L., S. gilo Raddi., S. melongena L., S. nitidibaccatum Bitter and S. paniculatum L. showed 2n = 24, whereas S. luteum Mill., S. nigrum L. and S. laciniatum Ait. showed 2n = 48, 2n = 72 and 2n = 92, respectively. All species demonstrated a symmetrical karyotype. The average chromosome size varied between diploid (1.95 μm) and polyploid (1.31 μm) species. Application of the CMA₃/DAPI technique showed two CMA₃ ⁺/DAPI^? terminal blocks in S. dulcamara, S. atropurpureum and S. luteum, indicating one homologous pair. In S. nitidibaccatum two large CMA₃ ⁺/DAPI^? segments were observed apart from several terminal blocks in almost all chromosomes. The same CMA₃ ⁺ telomeric standard was also found in prometaphases of S. luteum. Similar results were obtained with FISH with 45S rDNA probes: fluorochrome CMA₃ ⁺ telomeric blocks associated with satellites, with two blocks in S. atropurpureum, S. dulcamara, S. nitidibaccatum and S. luteum and four blocks in S. nigrum and S. lacinatum. Localization of species-specific markers was successful, allowing recognition of particular cytological features in most of the species analysed.     

<Emphasis Type="Italic">Myxobolus imparfinis</Emphasis> n. sp. (Myxozoa: Myxosporea), a new gill parasite of <Emphasis Type="Italic">Imparfinis mirini</Emphasis> Haseman (Siluriformes: Heptapteridae) in Brazil

A new species of myxozoan, Myxobolus imparfinis n. sp. is described based on material from the gills of Imparfinis mirini (Haseman) (Heptapteridae). Mature myxospores are round, measuring 7.1–8.4 (7.9 ± 0.3) μm in length, 4.5–6.2 (5.5 ± 0.5) μm in width and 3.1–4.2 (3.7 ± 0.3) μm in thickness. The polar capsules are of unequal size, the larger polar capsule measuring 3.4–4.5 (3.9 ± 0.3) μm in length and 1.4–2.0 (1.7 ± 0.1) μm in width and the smaller capsule measuring 3.1–3.8 (3.4 ± 0.2) μm in length and 1.2–1.8 (1.5 ± 0.2) μm in width. The polar filament presents 6–7 coils. Spores had a prevalence of infection of 75% (6/8). In histological analyses we detected the development site of spores in primary filaments, in afferent branchial artery, thus classifying the type of infection to the filamental type and vascular subtype. The phylogenetic analyses of a dataset including species Myxobolus Bütschli, 1882 and Henneguya Thélohan, 1892 from South America recovered M. imparfinis n. sp. as a sister species of Myxobolus flavus Carriero, Adriano, Silva, Ceccarelli & Maia, 2013. To our knowledge, this is the first record of a myxozoan species parasitising I. mirini.     

Cytogenetic studies on Bacillus grandii grandii and B. grandii benazzii (Insecta,Phasmatodea): karyotype description,constitutive heterochromatin and nucleolus organizer regions

The karyotype of the new Sicilian subspecies Bacillus grandii benazzii is described and compared to that of B. g. grandii. Both taxa share constant, very similar chromosome sets with 2n=34, XX, female and 2n=33, XO, male, the sex chromosomes being the third element of the complement. C-banding reveals that a centromeric heterochromatin mass is present on all chromosomes, but no interstitial bands are observed. Differences between karyotypes reside in the satellites which are located on pairs 13 and 16 in B. g. benazzii and only on pair 16 in B. g. grandii, in contracted metaphases larger satellites are positively C-banded. Furthermore, Ag-detected NORs are seen on pair 13 in B. g. benazzii and on pair 16 in B. g. grandii. Relationships between constitutive heterochromatin and NORs, NOR heteromorphism and the position of the 34-chromosome taxa within the genus are discussed.     

Comparative cytomolecular analyses reveal karyotype variability related to biogeographic and species richness patterns in Bombacoideae (Malvaceae)

Bombacoideae is one out of nine subfamilies of Malvaceae and encompasses 160 tree species. The subfamily is karyotypically characterized by small and numerous chromosomes and is traditionally known by a remarkable inter- and intraspecific chromosome number variation. We conducted a comparative cytogenetic analysis to investigate karyotype diversity and chromosome evolution within Bombacoideae. To achieve this, we performed new chromosome counts, CMA/DAPI double staining, genome size estimations, and localization of 5S and 45S rDNA by fluorescence in situ hybridization for 21 species distributed across the Bombacoideae phylogeny. We performed ancestral states reconstruction analyses to elucidate chromosome evolution and provide insights into the systematics and evolution of Bombacoideae in comparison with other Malvaceae species. Newly generated data on chromosome number on Bombacoideae revealed diploids (Ochroma (2n = 84), Cavanillesia, Pochota, Pseudobombax (2n = 88), and Pachira (2n = 92)) and polyploids (Adansonia digitata (2n = 160) and Eriotheca species (2n = ca. 194 and 2n = 276)). For most species, in situ hybridization revealed karyotype, with two pairs of 45S rDNA sites co-located with CMA⁺ bands, and 5S rDNA sites in only one chromosome pair. Taken together, our results provide support to the hypothesis of karyotypic stability in Bombacoideae. Only the Pachira s.l. clade displayed some variability in ploidy level, number of CMA⁺ bands and 45S rDNA sites, and genome size compared to other Bombacoideae clades. The Striated bark clade was characterized by comparatively small genomes and low cytomolecular variability. Karyotypic data were related to biogeographic and species richness patterns of Bombacoideae.     

Cytogenetics, geographical distribution, pollen stainability and fecundity of five diploid taxa of Santolina rosmarinifolia L. aggregate (Asteraceae: Anthemideae)

The chromosome analysis of Santolina rosmarinifolia subsp. rosmarinifolia, S. oblongifolia, S. semidentata subsp. semidentata, S. semidentata subsp. melidensis, S. canescens and the hybrid complex (S. rosmarinifolia subsp. rosmarinifolia, S. oblongifolia and their putative hybrids) shows that all the taxa are diploids (2n = 2x = 18; 18 + 1 or more B chromosomes, with 2n = 19, 20 only in the hybrid complex). The results show a conserved general structure of the karyotype (14m + 2sm + 2st), but in S. semidentata subsp. melidensis it is variable, with 14m + 2sm + 2st in ten individuals, 14m + (1m ? 1sm) + (1 m ? 1st) in nine individuals and 12m + (1m ? 1sm) + (1m ? 1st) + 2st + 1B in five individuals. Tetraploid individuals occurred in the diploid populations of S. rosmarinifolia subsp. rosmarinifolia and S. canescens, and their autopolyploid origin is discussed. Multivalent configurations at diakinesis, simple and double chromosome bridges and delayed disjunction of homologous and non-homologous chromosomes at anaphase I have negative effects on pollen stainability. The mean fructification percentage is moderate. The results suggest that the complex is a mosaic of introgressive hybrids.     

Chromosome numbers and karyotype of five species from Seriphidium (Asteraceae)

Chromosome data are important for elucidating intergeneric relationships and delimiting infrafamilial tribes in plants. This paper reports karyological data for 12 Seriphidium (Bess.) Poljak. species from China, of these, five count as new reports and the others have been reported elsewhere. We also report the tetraploid level in S. schrenkianum for the first time. The karyotype formulae and types for the five new reports are: S. schrenkianum (Ledeb.) Poljak. 2n = 4x = 36 = 22m + 12sm + 2st, S. sublessingianum (Kell.) Poljak. 2n = 2x = 18 = 14m + 4sm and S. transiliense (Poljak.) Poljak. 2n = 2x = 18 = 4M + 6m + 2m(SAT) + 4sm + 2sm(SAT), belong to 2A type; S. cinum (Berg. ex Poljak.) Poljak. 2n = 2x = 18 = 8m + 10sm and S. sawanense Y. R. Ling et C. J. Humphries 2n = 2x = 18 = 10m + 2m(SAT) + 6sm, belong to 2B type. Furthermore, we estimated karyotype asymmetry in the 12 species by using an intrachromosomal asymmetry index and an interchromosomal asymmetry index. The data increase information about the karyosystematics of Seriphidium.     

A cyto-evolutional study of Campanumoea Blume (Campanulaceae) and a possible pathway for secondary karyotype formation

Campanumoea is a small genus in the family Campanulaceae, with species divided into sections Campanumoea and Cyclocodon. Sixteen accessions from Campanumoea and related genera native to China were used to study their karyotype. The results showed that chromosome characteristics were different between the two sections. For Campanumoea, the karyotypic formula was 2n = 2X = 2m + 12sm + 2st = 16,3A and for Cyclocodon it was 2n = 2X = 6m + 12sm = 18,3B. These data, combined with chromosomal length characteristics, support the restoration of section Cyclocodon as a genus. However, the incorporation of section Campanumoea into Codonopsis requires more evidence. Comparison of chromosomal length and haploid set length revealed that chromosomal segment rearrangements occurred within sections of Campanumoea and between genera, with the difference within sections being greater than that between genera. Therefore, chromosomal segment rearrangements are present in Campanulaceae, implying that chromosomal segment rearrangement plays an important role in the evolution of diversity in Campanulaceae. By comparing the chromosomal characteristic in section Campanumoea and the genus Adenophora, we concluded that the secondary chromosome type such as n = 17, 18 would be derived by autopolyploidization of n = 9, and by chromosome fusion.     

Chromosome banding study of European catfish,Silurus glanis (Pisces,Siluridae)

The karyotype of European catfish (Silurus glanis L.) was analyzed sequentially by means of silver staining and the chromomycin A₃ (CMA₃)/distamycin A (DA)/DAPI fluorescence technique and by C-banding, respectively. The nucleolus organizer regions (NORs) were localized on the submetacentric pair No. 14. Brilliant CMA₃ fluorescent heterochromatin blocks corresponded to the NORs visualized by silver staining. No DA/DAPI-bright positive fluorescent patterns were detected while C-banding led to the detection of specific banding patterns on several chromosome pairs.—Using these banding data, the karyotype of S. glanis was redescribed.     

Molecular cytogenetic analysis of Haemulidae fish (Perciformes): Evidence of evolutionary conservation

Several fish species belonging to the family Haemulidae present a karyotype consisting of 48 acrocentric chromosomes (FN = 48), and apparently similar chromosomal microstructure, especially in genus Haemulon, representing a striking example of intrafamiliar chromosomal conservation. In this study, a more detailed cytogenetic analysis of the species Conodon nobilis and Pomadasys corvinaeformis was performed using C-banding, Ag-NOR, DAPI/CMA₃ staining, in situ digestion by distinct endonucleases and double-FISH to map the 18S and 5S ribosomal genes. Both species showed a similar karyotypic macrostructure with 2n = 48 acrocentric chromosomes and active ribosomal sites at interstitial position on long arms of chromosomal pair 18 and 24 in P. corvinaeformis and C. nobilis, respectively. These sites were the only CMA₃⁺/DAPI^-regions in the karyotype. Digestion with restriction enzymes revealed a low number of digestion sites in the heterochromatic segments of both species. The data indicate some degree of interspecific evolutionary diversification At the microstructural level, incorporated in a general pattern of extensive karyotypic conservatism. Thus, the interspecific reproductive isolation leading to phyletic diversification apparently occurred without the contribution of conspicuous karyotypic changes.     

Karyology of the Antarctic scallop Adamussium colbecki, with some comments on the karyological evolution of pectinids

Karyotype, location of the nucleolar organiser region (NOR) and heterochromatin presence and composition were studied in the Antarctic scallop Adamussium colbecki Smith, 1902. The karyotype exhibits 2n = 38 chromosomes with 11 pairs of metacentrics, 5 of submetacentrics, one subtelocentric and two telocentrics. Ag–NOR, CMA₃, DA/MM and NOR–FISH evidenced paracentromeric NORs on the short arm of 2nd pair chromosomes. Digestion with three restriction endonucleases followed by sequential staining with Giemsa, CMA₃ and DAPI evidenced on all chromosomes centromeric heterochromatin positive for both DAPI and CMA₃. In situ hybridisation analysis showed the presence of an AT-rich satellite DNA in the centromeric heterochromatin of several chromosomes. A mosaicism was detected in the germinal cell lines of one specimen, as in six of the 20 plates examined the set had 37 chromosomes with a missing pair of telocentrics and an unpaired metacentric. Comparison of the chromosome sets of all the pectinids studied to date and comparison with a phyletic tree obtained from molecular mitochondrial genes studies yielded good agreement between karyotype morphology and taxonomic classification.     

Karyological features and cytotaxonomy of the tribe Vernonieae (Asteraceae)

Chromosome numbers are reported for 29 populations of 19 Vernonieae taxa collected mainly in the northeastern region of Brazil. Among them, data for five genera (Blanchetia, Rolandra, Pithecoseris, Stilpnopappus and Vanillosmopsis) are here reported for the first time, and the first chromosome counts are presented for 12 species. Chromosome numbers are quite diverse among and sometimes within genera, especially in the controversial and large subtribe Vernoniinae. The numbers varied from 2n = 18 to 2n = ~72. The main karyoevolutionary mechanism seems to be dysploidy, while polyploidy is probably associated with ancient hybridization processes generating most paleotetraploid genera. All studied species presented semi-reticulated interphase nuclei and proximal-early condensing behavior in prophase to prometaphase. In one species (Vernonia condensata with 2n = 40) fluorochrome staining with CMA/DAPI revealed five chromosome pairs bearing subterminal CMA⁺/DAPI^? heterochromatin, probably NOR-associated, revealing the existence of low amounts of satellite DNA. The role of these features in the evolution of the tribe is discussed, revealing some interesting aspects for understanding of the Vernonieae karyoevolution, especially regarding neotropical members.     

Chromosome banding and FISH with rDNA probe in the diploid and tetraploid loach Misgurnus anguillicaudatus

The chromosomes of the diploid and tetraploid loach Misgurnus anguillicaudatus were analyzed by staining with Ag, chromomycin A₃ (CMA₃)/distamycin A (DA), and DA/4′,6-diamidino-2-phenylindole (DAPI), and using fluorescence in situ hybridization (FISH) with 5.8S + 28S rDNA as a probe. Nucleolus organizer regions (NORs) were mapped to the telomeric region of the short arms of the largest (first) metacentric chromosome pair in the diploid loach with 2n = 50 and the homologous quartet in the tetraploid loach with 4n = 100. The NORs were positive at the same region of the first metacentric chromosome for Ag and CMA₃/DA stainings, but negative for DA/DAPI staining. Four signals at the homologs within the same quartet suggest the duplication of the entire genome from diploid to tetraploid status. However, a size difference was detected between the rDNA signals by FISH and CMA₃ banding.