Karyotypes and geographical distribution of ricefishes from Yunnan,southwestern China

Morphometric and karyotypic studies were made on two species of ricefishes collected from Yunnan, southwestern China.Oryzias latipes from Yunnan had the same morphological and karyological characteristics asO. latipes collected from eastern China. The Yunnan populations had 2n, 46 chromosomes consisting of 3 metacentric, 8 submetacentric, 2 subtelocentric, and 10 acrocentric pairs, the arm number (NF) being 68 (2n=46, NF=68, 3M+8SM+2ST+10A). The karyotype was characterized by having a “large” metacentric pair and nucleolus organizer regions (NORs) on the short arms of a submetacentric pair.Oryzias minutilius from Yunnan had the same morphological characteristics asO. minuiillus from Thailand and Burma, although the karyotype was different from that collected from Thailand. The Yunnan population had 2n, 42 chromosomes consisting of 21 acrocentric pairs, NF being 42 (2n=42, NF=42, 21A). The karyotype was characterized by having NORs at the telomeric regions of an acrocentric pair.Oryzias latipes occurs widely on the eastern Yunnan Plateau where the climate is temperate or subtropical, whereasO. minutilius is found in Xishiangbanna, the southern low mountain areas of Yunnan, where the climate is tropical.     

The Karyotype of the flathead sculpin Megalocottus platycephalus taeniopterus (Kner, 1868) (Pisces: Cottidae) from Vostok Bay,Sea of Japan

For the first time, we studied the karyotype of the flathead sculpin Megalocottus platycephalus taeniopterus (Kner, 1868) from Vostok Bay of the Sea of Japan. The karyotype is stable: 2n = 42 (2 metacentric, 2 submeta-subtelocentric, 30 subtelocentric, and 8 acrocentric chromosomes), NF = 44 + 2. The nucleolar organizers (NOs) were identified using Ag banding in two pairs of chromosomes: in the telomeric parts of the short arm of the medium-size subtelocentric chromosome and the long arm of the large acrocentric chromosome. Variations in the number of nucleolar organizer chromosomes and in the number of NO staining blocks were found. Comparison of the karyotypes of M. p. taeniopterus and previously studied M. p. platycephalus (Pallas, 1814) from the northern Sea of Okhotsk revealed their similarity in the number and morphology of chromosomes and the number of chromosome arms and difference between the subspecies in the number and location of NO, which allows their discrimination.     

Karyotype and divergence of stream Dolly Varden from the Southern Sakhalin

The karyotype of stream Dolly Varden inhabiting a tributary of the Belaya River (the basin of Naiba River, southern Sakhalin) was determined (2n = 82 and NF = 98 + 2). According to the main characteristics (chromosome number and arm number, the presence of a pair of marker submeta-subtelocentric chromosomes with nucleolus organizer regions (NORs), one pair of large acrocentric chromosomes, and one pair of subtelocentric chromosomes), this karyotype is identical to the karyotype of anadromous southern Dolly Varden from Salvelinus malma krasheninnikovi of Primorye and Japan. However, in most stream Dolly Varden individuals, additional active nucleolus organizer regions (NORs) located in telomeric and paracentric regions of two to three pairs of acrocentric chromosomes were revealed. It is suggested that the stream and anadromous southern forms of Dolly Varden are evolutionarily related NORs that are silent in the anadromous souther form are active in the stream form. Possible causes of these differences in NOR activity are discussed.     

Karyotypic analysis of the gobiid fish genus Quietula Jordan and Evermann

The karyotypes of the two species of the gobiid fish genus Quietula, Q. y-cauda (Jenkins & Evermann) and Q. guaymasiae (Jenkins & Evermann), are reported for the first time. The karyotypes contained equal numbers of chromosomes (2 n =42) but differed in chromosome morphology. Quietula y-cauda has 42 acrocentric chromosomes. Quietula guaymasiae has six metacentric, four submetacentric, and 32 acrocentric chromosomes. It is suggested the karyotype of Q. guaymasiae might have been derived from that of Q. y-cauda. In addition, from comparison of the species' karyotypes of the genera Quietula and Gillichthys , it is possible the karyotype of Q. y-cauda might have been derived from that of Gillichthys mirabilis.     

Karyotype of the Snow Sculpin <Emphasis Type="Italic">Myoxocephalus brandti</Emphasis> Steindachner (Cottidae) from Peter the Great Bay,Sea of Japan

The karyotype of the snow sculpin Myoxocephalus brandti, 2n = 44, NF = 46, from Peter the Great Bay was studied. Two-armed chromosomes were presented by one pair of metacentric chromosomes of medium size; one-armed chromosomes included two pairs of large subtelocentric chromosomes and a pair of large acrocentric chromosomes. Ag-NOR-staining in the telomere vicinity revealed nucleolus-organizing regions in one metacentric chromosome and in one medium size acrocentric chromosome in one of the fishes, in two homological small acrocentric chromosomes in three fishes, and in one acrocentric chromosome of average size in six fishes. No difference between the male and female karyotypes and any type of variability was revealed. The karyotypes of the snow sculpin M. brandti and the frog sculpin M. stelleri were compared. Their distinctions and similarities were displayed.Original Russian Text Copyright ¢ 2005 by Biologiya Morya, Ryazanova.     

Comparative analysis of the karyotype of the sculpin Myoxocephalus ochotensis (Pisces: Cottidae) from the Odyan Bay of the Sea of Okhotsk

The karyotype of the endemic Okhotsk Sea sculpin Myoxocephalus ochotensis Schmidt (Cottidae) from Odyan Bay was studied. The number and morphology of chromosomes were determined, 2n = 42 (2 metacentric, 20 subtelocentric, and 20 acrocentric chromosomes), NF = 44. Variability of chromosome number was not revealed; no difference between male and female karyotypes was found. The karyotype of the Okhotsk sculpin M. ochotensis was compared with karyotypes of the Far East Steller’s M. stelleri (Tilesius), snow M. brandti (Steindachner), and plain M. jaok (Cuvier) sculpins, and to the European shorthorn sculpin M. scorpius (Linnaeus) from White Sea. Their similarities and distinctions were shown.     

Karyological differences of the Northern Dolly Varden Salvelinus malma malma and the white char Salvelinus albus from the Kamchatka River basin

The karyotypes of northern Dolly Varden and white char, sympathrically inhabiting the Kamchatka River basin, were studied. The karyotype of Dolly Varden was stable: 2n = 78 and NF = 98 + 2, while in white char, polymorphism and mosaicism for the chromosome number were revealed: 2n = 76-79, NF = 98 + 2. Using a routine chromosome staining technique, the karyotype of white char (2n = 78) was shown to be identical to that of Dolly Varden. In both karyotypes, similar sets of marker chromosomes were present: two pairs of submetacentric (SM), one pair of submeta-subtelocentric (SM-ST), one pair of large acrocentric (A), and one pair of large sub-telocentric (ST) chromosomes. However, the karyotypes of Dolly Varden and white char differed in the number and location of nucleolus organizer regions (NORs). In Dolly Varden, single NORs located in the telomeric regions of the marker SM-ST chromosomes were observed. In white char, NORs were multiple and located both in the telomeric regions of the marker SM-ST chromosomes and on the short and long arms of large ST chromosomes. The identical marker chromosomes indicate considerable phylogenetic relatedness between Dolly Varden and white char from the Kamchatka River basin. Variation in NORs provides evidence for the reproductive isolation of these chars and their species status.     

Karyotypes of two rare rodents, Hapalomys delacouri and Typhlomys cinereus (Mammalia, Rodentia), from Vietnam

Karyotypes of Hapalomys delacouri (Rodentia, Muridae) and Typhlomys cinereus (Rodentia, Platacanthomyidae) from Vietnam are described for the first time. The diploid karyotype of Hapalomys delacouri is 38 (NFa=48), consisting of six pairs of bi-armed and 12 pairs of acrocentric autosomes decreasing in size; plus a large metacentric X chromosome and Y chromosome, also metacentric, that is equal in size to the largest pair of acrocentric autosomes. The newly described karyotype differs significantly from that reported for Hapalomys delacouri from northern Thailand. The latter record very likely represents a different species of Hapalomys, possibly the taxon Hapalomys pasquieri described from north-central Laos.The diploid karyotype of Typhlomys cinereus is 38 (NF=48), consisting of five pairs of meta- to submetacentric and 14 pairs of acrocentric chromosomes varying in size from large to small; sex chromosomes were not defined.     

Chromosome evolution involving Robertsonian rearrangements in Xyrichthys fish (Labridae, Perciformes)

Three Xyrichthys fish (Labridae, Perciformes), X. pavo, X. dea, and X. twistii, were cytogenetically studied. X. pavo and X. dea had 2n = 44 chromosomes, which were all acrocentric. X. twistii had 2n = 22 chromosomes consisting of eighteen meta- and submetacentric and four acrocentric chromosomes. The cellular DNA contents of X. pavo and X. twistii measured using flow cytometry were nearly equal. These results suggest that the karyotype of X. twistii evolved by decreasing the number of chromosomes by fusion events, probably Robertsonian fusion. Cytogenetic relationships among the three species were surmized on the basis of features on the karyotypes and the NOR locations. A large gap in the chromosome number between 2n = 44 and 2n = 22 is an interesting feature related to the process of chromosome evolution.     

Cytogenetic characterization and description of an XX/XY1Y2 sex chromosome system in catfish Harttia carvalhoi (Siluriformes, Loricariidae)

Karyotypic and cytogenetic characteristics of catfish Harttia carvalhoi (Paraíba do Sul River basin, S?o Paulo State, Brazil) were investigated using differential staining techniques (C-banding, Ag-staining) and fluorescent in situ hybridization (FISH) with 18S and 5S rDNA probes. The diploid chromosome number of females was 2n = 52 and their karyotype was composed of nine pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric and four pairs of acrocentric chromosomes. The diploid chromosome number of males was invariably 2n = 53 and their karyotype consisted of one large unpaired metacentric, eight pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric, four pairs of acrocentric plus two middle-sized acrocentric chromosomes. The differences between female and male karyotypes indicated the presence of a sex chromosome system of XX/XY1Y2 type, where the X is the largest metacentric and Y1 and Y2 are the two additional middle-sized acrocentric chromosomes of the male karyotype. The major rDNA sites as revealed by FISH with an 18S rDNA probe were located in the pericentromeric region of the largest pair of acrocentric chromosomes. FISH with a 5S rDNA probe revealed two sites: an interstitial site located in the largest pair of acrocentric chromosomes, and a pericentromeric site in a smaller metacentric pair of chromosomes. Translocations or centric fusions in the ancestral 2n = 54 karyotype is hypothesized for the origin of such multiple sex chromosome systems where females are fixed translocation homozygotes whereas males are fixed translocation heterozygotes. The available cytogenetic data for representatives of the genus Harttia examined so far indicate large kayotype diversity.     

The characterization of somatic chromosomes of Gymnothorax unicolor (Delaroche, 1809) by C-banding and NOR staining (Osteichthyes,Anguilliformes)

The diploid chromosome number of Gymnothorax unicolor (Delaroche, 1809) is 2n=42, the karyotype comprising six pairs of meta-submetacentric and fifteen pairs of acrocentric chromosomes. C-positive chromatin is present in the centromeres of all chromosomes as well as in the paracentromeric regions of some chromosomes. A nucleolar organizer region was identified on the long arm of chromosome 9, near the centromere. This region is also positive to C-banding.Cytotaxonomical relationships are evidenced between the described karyotype and that of the related species Muraena helena.     

Chromosomal polymorphism of Rattus rattus (Linnaeus, 1758) (rodentia: muridae) in Central Anatolia

In this study, conventionally stained, C- and Ag-NOR banded karyotypes of Rattus rattus from Central Anatolia are presented. The karyotype of the specimens from Ankara and (Cankiri provinces consist of 2n = 38, NF = 60 and NFa = 58 while the karyotype of Kirikkale specimens consist of 2n = 38 and NFa = 59 due to a heteromorphic autosome pair. The X is a large to medium sized acrocentric and the Y chromosome is a small acrocentric in all examined specimens. Constitutive heterochromatin is located in the centromeric regions of all pairs of autosomes and the X chromosome. Nucleolar organizer regions (NORs) are located only in 3 autosome pairs.     

中国两种掌突蟾(锄足蟾科Pelobatidae,无尾目Anura)的细胞遗传学研究

本文对分布于云南境内的两种Leptolalax——L.ventripunctatus和L.alpinus的常规Giemsa核型、C-带和Ag-NORs作了研究,结果表明L.ventripunctatus的2n=22,20M 2T,NF=42,1对Ag-NORs位于5(?),并呈现异形现象,该区域亦显C-带正染;L.alpinus 2n=24,14M 4SM 6T,NF=42,1对Ag-NORs位于No.8短臂端部,并有随体联合现象。两种的着丝点区域均呈现C-带正染。     

Cytogenetic analysis of the tamaraw (Bubalus mindorensis): a comparison of R-banded karyotype and chromosomal distribution of centromeric satellite DNAs, telomeric sequence, and 18S-28S rRNA genes with domestic water buffaloes

The karyotype of the tamaraw (Bubalus mindorensis, 2n = 46) was investigated by RBG-banding technique and compared with those of the river and the swamp cytotypes of domestic water buffalo (B. bubalis). The tamaraw karyotype consisted of 6 submetacentric and 16 acrocentric autosome pairs (NAA = 56), and X and Y chromosomes. The RBG-banded karyotype of the three taxa had a high degree of homology, and the tamaraw karyotype could be explained by a Robertsonian translocation between chromosomes 7 and 15 and by a telomere-centromere tandem fusion between chromosomes 4p and 12 of the standardized river buffalo cytotype (2n = 50, NAA = 58). The buffalo satellite I and II DNAs were localized to the centromeric regions of all the tamaraw chromosomes. The biarmed chromosome 2 of the tamaraw resulting from the fusion between chromosomes 7 and 15 of the standard contained much larger amounts of the satellite I DNA than the other biarmed chromosomes, suggesting that this chromosome was formed by a relatively recent Robertsonian fusion. The (TTAGGG)n telomeric sequence was specifically localized to the telomeric region of all the buffalo chromosomes. The 18S + 28S rDNA was localized to the telomeric regions of the chromosomes 5p, 7, 19, 21, and 22 of the tamaraw and of their homologous chromosomes in the river and swamp buffalo cytotypes.     

Tandem and centric fusions in the chromosomal evolution of the South American phyllotines of the genus Auliscomys (Rodentia, cricetidae).

The karyotypes of three of the four extant species of the genus Auliscomys (A. micropus, living in central [2n = 32, NF = 34] and southern [2n = 34, NF = 36, 37] Chile; A. sublimis [2n = 28, NF = 32] and A. boliviensis [2n = 22, NF = 32], which inhabit the Andean Altiplano) were analyzed. Comparisons of G-, C-, and AgNOR-banded karyotypes showed that extensive conservation of entire chromosomes and chromosomal regions had occurred during the evolution of this genus, with centromeretelomere tandem fusions and centric fusions probably being the most frequent chromosome changes. A chromosomal phylogeny, based on the chromosome homoeologies detected and parsimonious analysis of the nature and distribution of the inferred chromosomal changes, is proposed. This hypothetical phylogeny assumes that the ancestral telocentric karyotype would have undergone three consecutive tandem fusions, first originating the 2n = 32 (NF = 34) karyomorph exhibited by present-day specimens of A. micropus captured in central Chile and then the 2n = 28 (NF = 32) karyotype of A. sublimis. Subsequent centric fusions involving the tandem-fusion products would presumably have generated the 2n = 22 (NF = 32) A. boliviensis karyotype. Assuming some conditions related to early geographic distribution, this chromosomal phylogeny is in agreement with a paleogeographic model, which explains the present distribution of living Auliscomys species mainly on the basis of geologic and climatic events.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chromosome banding and molecular cytogenetic study of two Mediterranean trachinoid fish species (Teleostei: Trachinidae, Uranoscopidae)

The chromosomes of Echiichthys vipera (Trachinidae) and Uranoscopus scaber (Uranoscopidae) were analyzed by means of various banding methods and fluorescence in situ hybridization (FISH) with telomeric and major rDNA probes, respectively. The karyotype of E. vipera was composed of 48 acrocentric chromosomes and NOR sites, as revealed by all detection methods, were situated pericentromerically on a single pair of middle-sized chromosomes. Blocks of constitutive heterochromatin were present in the pericentromeric regions of all pairs of chromosomes. The karyotype of U. scaber showed three karyomorphs: 2n = 30 (18 m + 12 a/st [m = metacentric, a = acrocentric and st = subtelocentric]), 2n = 28 (20 m + 8 a/st), 2n = 27 (21 m + 6 a/st). NORs, as revealed by FISH, were situated pericentromerically on a single pair of middle-sized chromosomes in spite of Ag-positive signals in the centromeres of all pairs of chromosomes. Robertsonian fusions were hypothesized for observed variation due to invariable number of chromosome arms FN = 48.     

Karyotype of the sculpin <Emphasis Type="Italic">Myoxocephalus jaok</Emphasis> (Pisces: Cottidae) from Peter the Great Bay,Sea of Japan

The karyotype of the sculpin Myoxocephalus jaok from the Ussuriisky, Amursky, and Vostok Bays was studied. It was found that 2n = 24, among the chromosomes there were 16 metacentric, 4 submetacentric, and 4 acrocentric, NF = 44. There was no variation in the number of chromosomes, and no differences between male and female karyotypes were revealed. A comparison of Myoxocephalus jaok, M. brandti and M. stelleri karyotypes was performed. The pronounced distinction of Myoxocephalus jaok karyotype resulting from chromosomal rearrangements was shown.     

Karyotype differentiation between two stickleback species (Gasterosteidae)

The stickleback family (Gasterosteidae) of fish is less than 40 million years old, yet stickleback species have diverged in both diploid chromosome number (2n) and morphology. We used comparative fluorescence in situ hybridization (FISH) on 2 stickleback species, Gasterosteus aculeatus (2n = 42) and Apeltes quadracus (2n = 46), to ascertain the types of chromosome rearrangements that differentiate these species. The A. quadracus karyotype contains more acrocentric and telocentric chromosomes than the G. aculeatus karyotype. By using bacterial artificial chromosome probes from G. aculeatus in our FISH screen, we found that 6 pericentric inversions and 2 chromosome fusions/fissions are responsible for the greater number of acrocentric and telocentric chromosomes in A. quadracus. While most populations of G. aculeatus have an XX/XY sex chromosome system, A. quadracus has a ZZ/ZW sex chromosome system, as previously reported. However, we discovered that a population of A. quadracus from Connecticut lacks heteromorphic sex chromosomes, providing evidence for unexpected sex chromosome diversity in this species.     

Cytogenetic study on Microtus guentheri (Danford and Alston, 1880) (mammalia: rodentia) from Turkey: constitutive heterochromatin distribution and nucleolar organizer regions

Conventionally stained, C- and Ag-NOR banded karyotypes of Guenther's vole, Microtus guentheri were studied from Turkey. The species possesses a karyotype of 2n = 54, NFa = 52 and NF = 54 in specimens from Kahramanmara? and Gaziantep provinces, whereas NF = 56 in females and NF = 55 in males were found in individuals from Kirikkale and Nev?ehir provinces. The X chromosome was a large acrocentric (NF = 54) or submetacentric (NF = 55, 56) while the Y chromosome was a small telocentric in all specimens examined. Blocks of constitutive heterochromatin were located in the pericentromeric areas of autosomes including the X chromosome. Nucleolar organizer regions (NORs) were located at the telomeric regions of the short arms of five acrocentric pairs and centromeric regions of two telocentric pairs in the Nev?ehir and Kirikkale specimens.     

同源四倍体青花菜的核型分析

以四倍体青花菜为材料,采用常规压片法进行核型分析和有丝分裂观察.结果表明:四倍体青花菜核型公式为2n=4x=36=16m+20sm(4 SAT),其中第3、4、7、8对为中着丝粒染色体,第1、2、5、6、9对为近中着丝粒染色体,第6对染色体具随体;核型类型属于2A型,为基本对称型;染色体相对长度组成为2n=36=16 M_2+20 M_1,表明该四倍体青花菜是二倍体加倍得到,为同源四倍体.在部分四倍体根尖中发现非整倍体细胞,其染色体数目变异较大;与二倍体相比,四倍体有丝分裂过程存在双核仁、体细胞配对、染色体桥等异常现象.