Chromosomal characteristics and karyotype evolution of Oxyopidae spiders (Araneae, Entelegynae)

We made a cytogenetic analysis of four species of Oxyopidae and compared it with the karyotype data of all species of this family. In Hamataliwa sp, the mitotic cells showed 2n♂ = 26+X(1)X(2) and telocentric chromosomes. The 2n♂ = 28, which has been described for only one oxyopid spider, is the highest diploid number reported for this family. Peucetia species exhibited distinct karyotype characteristics, i.e., 2n♂ = 20+X(1)X(2) in P. flava and 2n♂ = 20+X in P. rubrolineata, revealing interspecific chromosome variability within this genus. However, both Peucetia species exhibited telocentric chromosomes. The most unexpected karyotype was encountered in Oxyopes salticus, which presented 2n♂ = 10+X in most individuals and a predominance of biarmed chromosomes. Additionally, one male of the sample of O. salticus was heterozygous for a centric fusion that originated the first chromosomal pair and exhibited one supernumerary chromosome in some cells. Testicular nuclei of Hamataliwa sp and O. salticus revealed NORs on autosomal pairs, after silver impregnation. The majority of Oxyopidae spiders have their karyotype differentiated by both reduction in diploid number chromosome number and change of the sex chromosome system to X type; however, certain species retain the ancestral chromosome constitution 2n = 26+X1X2. The most remarkable karyotype differentiation occurred in O. salticus studied here, which showed the lowest diploid number ever observed in Oxyopidae and the second lowest registered for Entelegynae spiders.     

Karyotype, centric fusion polymorphism and chromosomal aberrations in captive-born mountain reedbuck (Redunca fulvorufula)

Chromosomes of fourteen captive-born mountain reedbucks (Redunca fulvorufula) have been investigated. The diploid chromosome number was 2n = 56 (FN = 60). The mountain reedbuck karyotype consists of 26 acrocentric and two biarmed chromosome pairs resulting from two centric fusions involving chromosomes 2 and 25, and 6 and 10, respectively. In some animals, 57 chromosomes were detected. Variation in the diploid number was found to be due to polymorphism for the centric fusion 6;10. Both X and Y chromosomes are large and acrocentric. The entire Y chromosome and the proximal part of the X chromosome consist of heterochromatin. The chromosomes X, 9 and 14 appeared to be of caprine type. Chromosome aberrations have been detected in two of the 14 animals investigated. A de novo formed Robertsonian translocation rob(6;13) was found in one female heterozygous for the fusion 6;10. CBG-banding revealed one block of centromeric heterochromatin in the de novo formed translocation rob(6;13) and also in the evolutionarily fixed centric fusions 6;10 and 2;25. One examined male homozygous for fusion 6;10, had a mosaic 56,XY/57,XYY karyotype, with 11% of analyzed cells containing two Y chromosomes. The findings were confirmed by cross-species fluorescence in situ hybridization (FISH) with bovine (Bos taurus L.) chromosome painting probes. The study demonstrates the relevance of cytogenetic screening in captive animals from zoological gardens.     

On the highest chromosome number in mammals

The mitotic and meiotic chromosomes of the semiaquatic rodent Ichthyomys pittieri (Rodentia, Cricetinae) from Venezuela were analyzed by means of conventional staining and several banding techniques. The diploid chromosome number of this rare species is 2n = 92, which is the highest value known for mammals. It is assumed that this exceptionally high chromosome number is the result of repeated centric fissions. The karyotype of I. pittieri was compared with that of Anotomys leander, for which a diploid number of 2n = 92 has also been reported. The karyological relationships existing within the Neotropical Cricetidae are summarized.     

Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). VII. G-banding analysis of Petrogale brachyotis and P. concinna: species with dramatically altered karyotypes.

G-banded metaphase preparations of cultured fibroblasts were used to construct the karyotypes of Petrogale brachyotis (2n = 18) and P. concinna (2n = 16). The two karyotypes differ significantly from the plesiomorphic karyotype of the genus and from those of all other Petrogale species examined. Petrogale brachyotis and P. concinna are characterised by three synapomorphies: a 1-10 centric fusion, a 3a-6 centric fusion, and a submetacentric chromosome 2 (2s). Both species also possess autapomorphies. Petrogale brachyotis is characterised by submetacentric chromosomes 5 (5s) and 4 (4sm), whereas P. concinna is characterised by a 5-9 centric fusion and a submetacentric chromosome 8 (8m). The 2s, 5s, 4sm, and 8m chromosomes all appear to be derived from their plesiomorphic homologs by centromeric transpositions. Although the rate of chromosome evolution varies considerably in Petrogale, the genus clearly exhibits karyotypic orthoselection, with all the autosomal rearrangements identified being either centric fusions or centromeric transpositions. This study also illustrates the potential for convergent evolution in chromosomally diverse groups and demonstrates the importance of G-banding studies for accurate identification of chromosome rearrangements.     

Three polymorphic chromosome systems of centric fusion type in a population of Manchurian sika deer (Cervus nippon hortulorum Swinhoe)

Chromosome studies of cells from skin and lung cultured in vitro from eleven Manchurian sika deer (Cervus nippon hortulorum Swinhoe) sampled from the population in Woburn deer park, England, revealed variations in the number of chromosomes between individual animals as follows: 2n = 68, 67, 66, 65, and 64. No intraindividual variation was found. The presumably normal chromosome complement (2n = 68) consisted almost exclusively of one-armed or t chromosomes. Only two autosomes and the Y chromosome of the male were two-armed or m chromosomes. The variations in the number of chromosomes in the population were due to centric fusions of one-armed autosomes into two-armed ones, building up three coexisting and integrating polymorphic systems of centric fusion or Robertsonian type.The work was supported by the Swedish Natural Science Research Council.     

Study on the inheritance of the centric fusion in the blue fox,Alopex lagopus

The inheritance of a centric fusion in the blue fox,Alopex lagopus was investigated in 38 litters (258 animals) originated from matings of parents (64 animals) with all possible diploid numbers of chromosomes (2n=50, 49 and 48). In general, the Robertsonian translocation was inherited in accordance with the Mendelian principle. However, in the matings of females with 2n=49 and males with 2n=50 a significantly higher number of animals with 2n=50 was observed in the progeny. Moreover, observations on two litters indicated thede novo occurrence of the centric fusion and fission.     

Karyotypes of Rana tagoi Okada with diploid number 28 in the Chausu Mountains of the Minamishinshu district of Nagano Prefecture, Japan (Anura: Ranidae)

Karyotypes of Tago's brown frog Rana tagoi from the Chausu mountains in Minamishinshu of Nagano Prefecture were examined by conventional Giemsa staining, C-banding and late replication (LR)-banding. Chromosome number was 2n = 28 in all cases. The 28 chromosomes consisted of four pairs (1-4) of large biarmed chromosomes, two pairs (5-6) of telocentric chromosomes and eight pairs (7-14) of small biarmed chromosomes. Chromosome pair 11 had a secondary constriction on the long arm. In females, the C-band on the long arm of chromosome pair 6 was detected in both homologs, but was absent from the arms of the homologs of chromosome pairs 5 and 9. In males, C-bands were found in the long arms of both homologs of chromosome pairs 5 and 6, were present only in one homolog of chromosome pair 5 for certain male specimens and found in only one homolog of chromosome pair 9. Specimens of R. tagoi (2n = 28) should thus have two pairs of telocentric chromosomes to provide the same number of chromosome arms, these originating quite likely from chromosome pair 1 in the 26-chromosome specimens by centric fission. Heteromorphic sex chromosomes of the XX-XY type in R. tagoi (2n = 28) in the Chausu mountains were identified. Karyotypes of tail-tip cells from a hybrid tadpole between female R. tagoi (2n = 26) from the Hinohara village in Tokyo and male R. tagoi (2n = 28) from the Chausu mountain population were examined by squash preparation. Chromosome number was 2n = 27 in all tadpoles. The 27 chromosomes consisted of one chromosome set of R. tagoi (2n = 28) and one of R. tagoi (2n = 26).     

A Robertsonian translocation, rob(2;28), found in Vietnamese cattle

A new Robertsonian translocation, rob(2;28), was discovered in a local population of the Vietnamese Cattle. The animal (2n = 59, XY) was found by Q- and R-banding to be a heterozygous carrier of a centric fusion translocation involving chromosomes 2 and 28. FISH analysis using a bovine satellite I DNA probe demonstrated that the centromeric heterochromatin block of the rob(2;28) chromosome become much smaller than its ancestors suggesting a monocentric nature of this centric fusion. This is the first report identifying a Robertsonian translocation in Southeast Asian cattle by karyotyping of banded chromosomes.     

Centric fusion differences among Oryx dammah, O. gazella, and O. leucoryx (Artiodactyla, Bovidae)

G- and C-banded karyotypes of the genus Oryx were compared using the standard karyotype of Bos taurus. Chromosomal complements were 2n = 56 in O. gazella gazella, 2n = 58 in O. g. beisa and O. g. callotis, 2n = 56-58 in O. dammah, and 2n = 57-58 in O. leucoryx. The number of autosomal arms in all karyotypes was 58. Nearly all variation in diploid number was the result of three independent centric fusions, but one 2n = 57 specimen of O. g. gazella deviated from the normal complement of 2n = 56 due to XXY aneuploidy. A 2;17 centric fusion was fixed in O. g. gazella, whereas O. g. beisa and O. g. callotis lacked this fusion and had indistinguishable karyotypes. Oryx dammah was polymorphic for a 2;15 centric fusion, and O. leucoryx was polymorphic for an 18;19 centric fusion. The five Oryx taxa shared a fixed 1;25 centric fusion; the small acrocentric element involved in the 1;25 fusion was identified by fluorescence in situ hybridization using a cosmid specific to Bos chromosome 25. The X and Y chromosomes were also conserved among the five taxa. Oryx g. gazella differed from the other Oryx species because of the fixed 2;17 centric fusion. This difference reflects an apparently longer period of geographic isolation between O. g. gazella and other populations of Oryx, and it is consistent with the classification of O. gazella and O. beisa as distinct species (see Kingdon, 1997). The lack of monobrachial relationships among the Oryx taxa indicates that sterility barriers between species have not developed. Viability of hybrid offspring constitutes a threat to captive breeding programs designed for endangered species conservation; in the case of Oryx, the 2;15, 2;17, and 18;19 metacentrics could serve as marker chromosomes for assessing hybridization between certain Oryx taxa.     

中国云南果蝇属暗果蝇种组的核型分化

观察了新近发现于我国云南的果蝇属暗果蝇种组(Drosophila obscura species group)种类D．luguensis、D．dianensis和D．limingi的有丝分裂中期核型,并将3个种的核型与各自的近缘种类进行了比较。D．luguensis具2n=12条染色体,包括3对中央着丝粒(V形)染色体、2对近端着丝粒(棒状)染色体以及1对微小(点状)染色体。其中X和Y染色体均为中央着丝粒染色体。D．dianensis和D．limingi具2n=10条染色体,包括1对大的V形常染色体,1对小的V形常染色体,2对J形(亚中着丝粒型)常染色体和1对点状染色体。其中X染色体为J形,Y染色体为短棒状。基于核型比较的结果以及D．sinobscura亚组地理分布的资料,结合种间系统发育关系研究结果,认为D．luguensis可能保留了该亚组祖先种类的核型。D．sinobscum的核型(2n=12：2V,1J,2R,1D)可能由一个pre-“sinobscura-hubeiensis”谱系的一个分支通过臂间倒位演化而来,而D．hubeiensis的核型(2n=10：4V,1D)可能由该谱系的另一分支通过着丝粒融合(2对近端着丝粒常染色体的融合)而形成。推测在D．dianensis和近缘欧洲种D．subsilvestris(2n=12：3V,2R,1D)间、D．limingi和东亚近缘种D．tsukubaensis(2n=12：3V,2R,1D)间的物种分化过程中,可能有相似的染色体变异类型发生。     

Evidence for eight tandem and five centric fusions in the evolution of the karyotype ofAethomys namaquensis A. Smith (Rodentia: Muridae)

G- and C-banded chromosomes ofAethomys namaquensis (2n=24),A. chrysophilus (2n=44), andPraomys coucha (2n=36) are compared and contrasted with publised material on Australian Muridae and North American Sigmodontidae. Direction and types of chromosomal rearrangements are established using cladistic methodology. An acrocentric morphology for chromosomes 5, 14, 15 and 20 (numbering system fromPeromyscus) are proposed as primitive for the common ancestor of the Muridae and Sigmodontidae rodent lineages. Reduced diploid number ofAethomys namaquensis is derived by eight tandem and five centric fusions since divergence from the common ancestor withA. chrysophilus. The two species ofAethomys share one derived metacentric chromosome that distinguishes them fromPraomys. Praomys has unique chromosomes which can be derived from the proposed primitive condition by five centric fusions and five pericentric inversions. It is concluded that karyotypic orthoselection for tandem and centric fusions is best explained by cellular or biochemical mechanisms rather than variation in population characteristics.     

Karyotaxonomical analysis in the genusAngelica (Umbelliferae)

Morphometric karyotype characters were studied in 25Angelica spp. (Umbelliferae, Apioideae) and in one species of the related genusTommasinia. For three species the chromosome numbers are new. In our study the majority of the species investigated are diploids with 2n = 22, some are tetraploids with 2n = 44 (for these tetraploids also diploid cytotypes are reported in the literature). Among the diploid species,A. miqueliana has a distinct karyotype consisting of submetacentric and acrocentric chromosomes only, the remaining diploids with 2n = 22 as well as tetraploids with 2n = 44 have rather symmetrical karyotypes, consisting of metacentric and submetacentric chromosomes. The very different chromosome number 2n = 28 has been found inA. gmelinii. Its karyotype includes two distinct groups of chromosomes: 8 pairs of rather large metacentrics and submetacentrics and 6 pairs of very short and asymmetrical chromosomes. Chromosome numbers and structures appear to be useful in the taxonomy of some intrageneric taxa inAngelica.     

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.     

Karyotype analysis of mithun (Bos frontalis) and mithun bull x Brahman cow hybrids

We examined the cytogenetics of mithun (Bos frontalis), a domesticated version of the Asian gaur, and hybrids (F(1) generation) produced by artificial insemination of Brahman cows (Bos indicus) with mithun semen. Reproductive potential was also examined in the F(1) generation and a backcrossed heifer for utilization of heterosis. Metaphase chromosome spreads were examined by conventional staining and fluorescence in situ hybridization hybridized with the entire chromosome 1 of mithun as a specific probe. Chromosome 1 of mithun was found to be equivalent to Bos taurus chromosomes 2 and 28. The karyotype of the female mithun (N = 4) comprised 58 chromosomes, including 54 acrocentric and four large submetacentric chromosomes, without the four acrocentric chromosomes found in the domesticated species B. indicus. However, one of the four female mithuns with a normal mithun phenotype had an abnormal karyotype (2n = 59), indicating introgression from B. taurus or B. indicus. The F(1) karyotypes (N = 6, 3♂3♀) of the mithun bull × Brahman cow cross had 2n = 59, intermediate between their parents; they were consistent heterozygous carriers with a centric fusion involving rob(2;28), as expected. Two pronounced red signals were seen in the mithun karyotypes, three red signals in the mithun × Brahman hybrids, and four red signals in the Brahman cattle, in good agreement with centric fusion of bovine rob(2;28). The female backcross hybrid (N = 1) with 2n = 59 had a similar chromosome configuration to the F(1) karyotypes and had rob(2;28). Such female backcross hybrids normally reproduce; however, the F(1) bulls (N = 3) had not yet generated normal sperm at 24 months.     

三褶虾脊兰的核型分析

采用压片法研究了三褶虾脊兰[Calanthe triplicata(Willem.)Ames]的染色体数目和核型.结果表明:三褶虾脊兰的染色体数目2n=38,为二倍体,核型公式为2n=2x=38=28m 8sm 2st.主要由中部和近中部着丝点染色体组成.核型分类为2B型,比较对称.     

Cytogenetics and reproduction of sheep with multiple centric fusions (Robertsonian translocations)

The significance of centric fusions (Robertsonian translocations) in domestic animals, with special reference to sheep, is reviewed. The mating is described of a further 856 ewes with either a normal chromosome number 2n = 54 or carrying one or more of the three different translocations (centric fusions) t1, t2 and t3 in various heterozygous and homozygous arrangements. Rams which were used in the matings were homozygous for one of the translocation chromosomes (2n = 52), double heterozygotes (2n = 52), triple heterozygotes (2n = 51) or were carriers of 4 translocation chromosomes (2n = 50) and 5 translocation chromosomes (2n = 49). A remarkably even distribution of segregation products was recorded in the progeny of all combinations of translocation ewes x translocation rams in those groups in which sufficient animals were available for statistical analysis. Forty-eight chromosomally different groups of animals were mated. Further, the overall fertility of the translocation sheep, measured by conception rate to first service, lambing percentage and number of ewes which did not breed a lamb, was not significantly different from New Zealand national sheep breeding data. In some groups the poorer reproductive performance could be explained by the age structure of the flock and inbreeding depression, which probably affected the performance of some animals. Sheep with progressively decreasing chromosome numbers, due to centric fusion, 2n = 50, 2n = 49 and 2n = 48, are reported. The 2n = 48 category represents a triple homozygous ewe and a triple homozygous ram and is the first report of the viable evolution of such domestic animals. Less than 1% of phenotypically abnormal lambs were recorded in a total of 1995 progeny born over 10 years. It is now considered that there is little or no evidence to suggest that centric fusions in a variety of combinations affect the total productive fitness of domestic sheep. It is suggested that future research should be more actively directed to understanding their genetic significance.     

Chromosome banding in three species of <Emphasis Type="Italic">Hypsiboas</Emphasis> (Hylidae,Hylinae), with special reference to a new case of B-chromosome in anuran frogs and to the reduction of the diploid number of 2n = 24 to 2n = 22 in the genus

The chromosomes of hylids Hypsiboas albopunctatus, H. raniceps, and H. crepitans from Brazil were analyzed with standard and differential staining techniques. The former species presented 2n = 22 and 2n = 23 karyotypes, the odd diploid number is due to the presence of an extra element interpreted as B chromosome. Although morphologically very similar to the small-sized chromosomes of the A complement, the B was promptly recognized, even under standard staining, on the basis of some characteristics that are usually attributed to this particular class of chromosomes. The two other species have 2n = 24, which is the chromosome number usually found in the species of Hypsiboas karyotyped so far. This means that 2n = 22 is a deviant diploid number, resulted from a structural rearrangement, altering the chromosome number of 2n = 24 to 2n = 22. Based on new chromosome data, some possibilities were evaluated for the origin of B chromosome in Hypsiboas albopunctatus, as well as the karyotypic evolution in the genus, leading to the reduction in the diploid number of 2n = 24 to 2n = 22.     

Chromosome evolution in the Salmonidae (Pisces): an update

The karyotypes of salmonid fishes including taxa in the three subfamilies Coregoninae, Thymallinae and Salmoninae are described. This review is an update of the (Hartley, 1987) review of the chromosomes of salmonid fishes. As described in the previous review, the karyotypes of salmonid fishes fall into two main categories based on chromosome numbers: the type A karyotypes have diploid numbers close to 80 with approximately 100 chromosome arms (2n = 80, NF = 100), and the type B karyotypes have diploid numbers close to 60 with approximately 100 chromosome arms (2n = 60, NF = 100). In this paper we have proposed additional sub categories based on variation in the number of chromosome arms: the A' type with NF = 110-120, the A" type with NF greater than 140, and the B' type with NF less than 80. Two modes of chromosome evolution are found in the salmonids: in the Coregoninae and the Salmoninae the chromosomes have evolved by centric fusions of the Robertsonian type decreasing chromosome numbers (2n) while retaining chromosome arm numbers (NF) close to that found in the hypothetical tetraploid ancestor so that most extant taxa have either type A or type B karyotypes. In the Thymallinae, the chromosomes have evolved by inversions so that chromosome arm numbers (NF) have increased but chromosome numbers (2n) close to the karyotype of the hypothetical tetraploid ancestor have been retained and all taxa have type A' karyotypes. Most of the taxa with type B karyotypes in the Coregoninae and Salmoninae are members of the genus Oncorhynchus, although at least one example of type B karyotypes is found in all of the other genera. These taxa either have an anadromous life history or are found in specialized lacustrine environments. Selection for increases or decreases in genetic recombination as proposed by Qumsiyeh, 1994 could have been involved in the evolution of chromosome number in salmonid fishes.     

Complex sex chromosome system in Eigenmannia sp. (Pisces,Gymnotiformes)

Chromosomes of Eigenmannia sp. (7 males and 15 females) collected from the Tietê River in Botucatu (SP, Brazil) were examined from gill, kidney and testicular cells. The diploid chromosome number in males was 2n=31 and in females, 2n=32. In both sexes the number of chromosomal arms was 40. The difference in diploid number was due to the fusion of two acrocentrics. Mitotic and meiotic studies suggested that one of the fused acrocentrics was the Y chromosome. The sex-determining mechanism in Eigenmannia sp. could therefore be XX, AA in the female and X, \-YA A in the males. One of the males presented 2n=30 chromosomes due to the occurrence of another fusion of acrocentrics. C-banding analysis of the mitotic chromosomes revealed constitutive heterochromatin in the centromeric regions of all acrocentrics. However, small metacentrics were C-band negative. The YA chromosome is C-band negative except for a small amount of heterochromatin in the centromeric region. The nucleolar organizer region as identified by Ag-staining is present in the interstitial region of chromosome pair No. 10.     

Chromosome evolution of the blue sheep/bharal (Pseudois nayaur)

A male dwarf blue sheep was collected 60 km south of Batang east to the Jinsha Jiang river, and a male Subei blue sheep (Greater form) was collected from Gansu, China, representing two geographically separated blue sheep forms. Chromosome preparations were prepared from fibroblast cultures. The dwarf blue sheep has a 2n = 54 and a karyotype with three biarmed formations that resulted from acrocentric chromosome fusions (based on the 2n = 60 Capra autosomal equivalents) 14p/5q, 27p/1q, and 29p/2q from the largest to the smallest biarmed chromosome, respectively. The 14p/5q fusion is metacentric, whereas the 27p/1q and 29p/2q are submetacentric. The Subei blue sheep had a 2n = 56, with only the 27p/1q and 29p/2q biarmed chromosome fusions. The remainder of the chromosomes in both blue sheep are acrocentric; the X is the largest acrocentric chromosome and the Y is a minute biarmed chromosome. Our observation is one evidence showing that chromosome evolution within blue sheep has followed a series of centric fusions resulting in the reduction of chromosome number, which is typical of all extant genera within the tribe Caprini.