Karyotype and Classification Status of Cansumys canus (Cricetidea,Rodentia )
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The mitotic chromosomes of Cansumys canus , from Ningshan,Shaanxi P rovi nce of China were analyzed by conventional, C banding, and Silver staining tec hn iques The species has a diploid number of 24, consists of 16 metacentrics, 4 s ubmetacentrics,2 subtelocetrics and 2 telocentrics Because of no male specime ns it is not determined the sex chromosomes Centromeric C bands were found in 2 pairs of chromosomes and a large heterochromatin block in long arm of one pair of subtelocentric chromosomes Silver stained NORs were found on the three to four pairs of chromosomes As the comparisons of the results with the chromosom e of the species Tscherskia (Cricetulus) triton [2n=28, 22 t + 4 m + XY (s t, m )] and other species in the Genus Cricetulus , there are several differences amo ng them in the diploid chromosome number and karyotypes We suggest that Cans umys canus should be one valid speciesCite
The karyotypes of three species of wood mice have been studied by banding techniques (G-,C- and Ag-staining).Three species have the same diploid number,2n=48.All chromosomes in the complement of A.draco are acrocentrics.The karyotype of A.peninsulae consists of 22 pairs of acrocentrics,1 pair of metacentrics,X and Y are acrocentrics.However,the karyotype of A.latronum consists of 13 pairs of acroentrics,2 pair of subacrocentrics,1 pair of submetacentric,7 pairs of metacentrics,X chromosome is a acrocentric.The G-banded,C-banded and silver-stained karyotypes have been observed.G-banding allows to identify all chromosome pairs in three species.C-banding reveals centromeric heterochromatin in all chromosomes in A.draco.In the C-banded karyotype of A.peninsulae,the centromeric heterochromatin is found in all chromosomes,however,the centromeric C-bands of Nos.7,11,15,21,22 are very fanitly stained even negative,there are also telomeric C-bands in Nos.2,4,7.The Y chromosomes of A.draco and A.peninsulae are whole heterochromatin.The centromeric C-bands of all chromosomes are positive in the C-banded karyotype of A.latronum,but the centromeric C-bands in Nos.3,4,10,12,13 are very fanitly stained.Ag-NORs are predominantly located at Nos.7,8,18,21,22 in A.draco.While Ag-NORs are found in Nos.7,8 in A.peninsulae and A.latronum,respectively.The polymorphism of Ag-NORs of No.22 (in A.draco) and No.7 (in A.peninsulae and A.latronum) is found.Moreover,the classification of three species has also been discussed.
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The karyotypcs of three species of Genus Cricetulus, namely ,C.triton, C.Longicaudatus and C. barabensis were examined and described.
C. triton has 28 chromosomes. the karyotype consists of 11 pairs of large to medium acrocentrics, 2 pairs of very small metacentrics, and a medium subtelocentric X and a small metacentric Y chromosomes.
C. longicaudatus has a diploid number of 24.Its karyotype is composed of 4 pairs of large to medium metacentrics, 3 pairs of large and medium subtelocentrics, 4 pairs of medium acrocentrics and a large metacentric X and a submetacentric Y chromosomes; Y being also large in size。
The diploid number of the chromosomes of C.barabensis is 22.Thekary-otype contains 4 pairs of very large to large metacentrics, 3 pairs ofsmall metacentrics and 3 pairs of medium Subtelocentrics;the sex chromosomes are represented by a large metacentric X and a medium submetacentric Y.
This paper presents a comparison of the karyotypes of the three species stated above with the chromosomal characters of C. eversmanni and C. cu-rtatus as described by Matthey ( 1961 ) , and C. migratorius by Yerganian (1964 ) . Results indicate:
1. the six species of the genus can be identified by their chromosome numbers and karyotypes;
2. Among these species C. longicaudatus, C. migratorius and C. barabensis are very closely related, whereas C. triton is most divergent;
3. The karyotype of C. triton is more primitive. Thus, it may be suggested that this species must have diverged at an early period during the course of evolution;
4. The karyotype evolution of the six species has occured through avaty of chromosomal mutation, and the most frequent of these are Robcrtsonian fusions, while chromosome breaks, translocalions and inversions arc less.
Chromosome number
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G-banding, C-banding, and silver staining techniques were used to analyze the chromosomes of <i>Trichomys apereoides</i>. In a sample of 22 specimens the diploid number was 2n = 30, with several pairs of biarmed chromosomes and a large metacentric (pair 1) with a secondary constriction, or nucleolar organizing region (NOR), in the short arm. One male had a heteromorphic pair 1, with only one NOR-bearing homolog. C-bands showed constitutive heterochromatin in the centromeric region of almost all autosomes. The X has a large block in the proximal region and an interstitial small band in the long arm. The Y is totally heterochromatic. One heteromorphic female with an increased C-band block in one of the X chromosomes was observed. The Y is a small submetacentric; one male showed a metacentric Y, resulting probably from a pericentric inversion. The sexual bivalent and the synaptonemal complexes of all autosomal bivalents were revealed by silver staining in pachytene cells.
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Fea's tree rat (Chiromyscus chiropus) is a very rare species which there are only a few specimens in the world. The chromosomes of two male specimens, collected from Xishuanbanna, Yunnan, are analysed by several banding technique (G-, C-bands, as well as Ag-staining). The diploid chromosome number is 22, and autosomes comprise 5 pairs of metacentrics, 2 pairs of subacrocentrics, and 3 pairs of acrocentrics. The X chromosome is a acrocentric, and Y is a micro-chromosome, almost a point, which could be a marker chromosome of the species and the genus. The centromeric C-bands are very faint, and C-bands of Nos. 1, 2, 9 and Y chromosome are negative. Only one pair Ag-NORs was found on No. 10 in the silver-stained karyotype. The relationship between morphologic and chromosomal features was discussed, and C-banded karyotype evolutionary trend has also been discussed. Moreover, the conventional karyotype of Niviventer confucianus was described.
G banding
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Secondary constriction
Hyla
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SUMMARYThe karyotype of stoneloach, Noemacheilus barbatulus from Utrata river was studied by conventional Giemsa staining, Ag-NOR technique and C-banding. The diploid chromosome number 2n = 50, was composed of 4 pairs of metacentric, 10 pairs of submetacentric and 11 pairs of subtelo- to acrocentric chromosomes (NF = 78). The NORs bearing chromosomes were from the biggest metacentric pair and they were located on terminal position. This region was also positive for C—banding. The massive heterochromatin block was also localized on the arms, on one side of centromer, on the second pair of metacentric chromosomes. Almost all other biarmed and uniarmed elements of chromosome set had C-positive heterochromatin in the centromers. Most of the species studied from subfamily Noemacheilinæ had diploid chromosomes number 2n = 50. In comparison with the fish from subfamily Cobitidinæ a lack of interpopulation chromosomal variability was observed. The results of karyotype of Noemacheilus barbatulus in comparison with the previously conducted studies are thus suggesting karyological stability.
Subfamily
Giemsa stain
Constitutive heterochromatin
Microchromosome
Cytotaxonomy
G banding
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Differential chromosomal stainings for various species belonging to genera in the tribe Cricetini of the Eurasian Cricetinae including Cricetus, Cricetulus, Tscherskia, Phodopus, and Mesocricetus are available (Gamperl et al. 1978; Kartavtseva et al. 1979; Popescu and DiPaolo 1980; Kral et al. 1984). Hitherto, however, no differential chromosomes stainings for species in the genus Allocricetulus have been described and the phylogenetic position of this genus in the Cricetini, based on chromosomal data, has not been determined. The Eversmann’s hamster Allocricetus eversmanni Brandt, 1859 occurs in dry steppes and semi-deserts between the Volga and Ural rivers in Russia and in Kazakhstan, and includes three subspecies. The karyotype of A. eversmanni (2n = 26) was first described by Matthey (1960) from Kazakhstan, then subsequently those for subspecies, A. e. eversmanni and A. e. beljaevi (2n = 26, NF = 40: 8M + 10T + 6ST, X – SM, Y – SM) and A. e. pseudocurtatus (2n = 26; NF = 38: 8M + 12T + 4ST, X – M/SM, Y – SM/ST) were described. Kartavtseva and Vorontsov (1992) found distinctions in the morphology of one pair of large autosomes, pair no. 5, and in the size and morphology of the Y-chromosome and have suggested that the difference in the chromosome pair no. 5 appeared in A. e. pseudocurtatus. One female A. e. eversmanni was captured in the vicinity of Djakovka Village, Saratov Region, near the Lower Volga River, Russia. Chromosome preparations were obtained from bone marrow cells. After colcemidtreatment and hypotonic treatment with KCl-solution, the cells were fixed with acetic-methanol (1 : 3) and air or flame-dried. We arranged the chromosomes as described previously by Kartavtseva and Vorontsov (1992). The procedure of tripsin treatment was used for G-banding (Seabright 1971). The distribution of heterochromatin in chromosomes was shown using Sumner’s (1972) modified C-banding technique. The locations of nucleolar organizer regions (NORs) of metaphase chromosomes were determined after 50% aqueous AgNO3 treatment for 12 hours at 50–60°C (Bloom and Goodpasture 1976). The karyotype consisted of 24 autosomes (2n = 26, NF = 40): four pairs of metacentrics (M) and submetacentrics (SM): one pair large, one pair medium and two pairs small, two pairs of large subtelocentrics (ST) and six pairs of acrocentrics (A), ranging from medium-sized to small. The X chromosome was a medium sized submetacentric (Fig. 1). Differential G-staining made it possible to define the homologues in the karyotype (Fig. 1a). The short arm of the large subtelocentric no. 5 had no clear bands, while the short arm of the large subtelocentric no. 6 had a clear band in the pericentromeric region. The least acrocentrics nos. 11 and 12 had no clear bands. The C-staining of chromosomes obtained a low amount of heterochromatin in A. e. eversmanni in biarmed chromosomes nos. 1, 2, 5, 6, and acrocentric no. 7 had no positive band. The two pairs of small metacentrics nos. 3, 4 and small acrocentrics nos. 8–12 had heterochromatin in pericentromeric areas. The X chromosome carried one dark C-block in the pericentromeric region of the short arm (Fig. 1b). NORs were ascertained in five pairs of chromosomes. In pairs 2, 4, and 5 of biarmed chromosomes, the NORs were found at the telomeric ends (pair 5 had NORs in short arms). In the acrocentric pairs 8 and 10, very small NORs were observed at the centromeric positions (Fig. 1c). Earlier we assumed that distinction among A. e. eversmanni, A. e. beljaevi and A. e. pseudocurtatus based on the occurrence of deletion in the short arm of
Subspecies
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In this paper the karyotype,C-banding and Ag-NORs of Semilabeo prochilus from Jin Sha River system (Yunnan Province) have been studied.The diploid number of Semilabeo prochilus is 50(16 m+20 sm+14 st)and NF=86.The centromeric distribution of heterchromatin has been demonstraed in most of chromosomes.The short arm of No.1 was found to be a complete heterochromatin.oreover,the interstitial heterochromatin has observed on the long arm Nos.9,10,11.Silver-staining showed 7 Ag-NORs at Nos.10,11,13 chromosomes,but only one Ag-NORs appeared in the No.13.Based on the above data,Semilabeo prochilus might be specilized species in genus Semilabeo.
Constitutive heterochromatin
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The chromosome C-banding technique has been employed in studying C-karyotypes of two grasshoppers species of Genus Eotmethis from Pamphagidae, namely, E. tiantsuensis and E. jintaiensis which are only distributed in Northwest China. Spermatogenous mitotic metaphases and primary spermatocyte meiotic metaphases (metaphase 1) of two species are analyzed. The main points of results are as follows. Either basic numbers of chromosomes (2n male symbol) and karyotypes formulae or centromeres location of two species are coincident with the preceding studies. These provide a further backing for the karyotype stability in the Pamphagidae. The corresponding values of chromosome relative length are closer between E. tiantsuensis and E.jintaiensis, and there are no obvious differences in their total C-heterochromatin contents, No.3, 4, 9 and X chromosomes of both species have showed larger and darkly stained acrocentric C-bands, and No.2 chromosomes of both species have consistently showed a distinct mid-stained interstitial C-band proximal to the median of chromosome. The above-metioned facts reflect a close relation between the two species in their systematic development. In addition, the differences in the C-banding patterns between two species are reflected more or less in No.1, No.7 and No.8 chromosomes, especially obvious variations in the size and stained degree of acrocentric C-blocks of corresponding No.7 and No.8 chromosomes between the two species.
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The chromosome spreading of metaphase kidney cells was conducted by colchicine-low concentration-air drying technique in Leuciscus merzbacheri,and Ag-NORs,C-band and G-band were analyzed in this paper.L.merzbacheri had a diploid chromosome number of 2n = 50,its karyotype formula was 18m + 14sm + 6st + 12t,NF = 82,and sex chromosome was not found.The Ag-NORs polymorphisms were individually specific,1-2 in number,and the frequency of single Ag-NORs was the lowest(10%),while the frequency of 2 Ag-NORs was the highest(70%).Ag-NORs mostly appeared in the chromosome m1 and m4.The associations of Ag-NORs were not observed.All the chromosomes were C-band positive,and composed of centromeric C-band and telocentric C-band.The G-bands in homologous chromosomes were basically coincident,and distinctive character of banding number and distribution could be identified in every homologous chromosome.
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