甘肃仓鼠的分类地位

自1928年Allen发表采自甘肃卓尼的甘肃仓鼠(Cansumys canus)以来,对其分类地位的争论就没有停止,不同学者从形态学和生态学方面研究得出了不同的结论。为了确认Allen所命名的甘肃仓鼠的分类地位,本研究利用形态性状和遗传性状,比较研究了甘肃、宁夏标本(包括模式产地标本)与华北、东北大仓鼠标本共计169只。结果显示:甘肃、宁夏地区标本身体及头骨量度与大仓鼠指名亚种、东北亚种间大多无显著性差异;地理分布连续,其间无隔离,也无地理重叠;生态特征与华北、东北的大仓鼠相似;基于线粒体DNA D-loop区序列的遗传变异分析表明,甘肃、宁夏地区种群与大仓鼠东北亚种种群关系较大仓鼠东北亚种种群与指名亚种种群关系更近;单倍型演化关系显示,指名亚种种群和东北亚种种群分别独立地由甘肃种群单倍型衍生而来,并且三个种群单倍型之间的分歧较浅,没有形成种上的分歧程度。据此,甘肃、宁夏地区“甘肃仓鼠”应为大仓鼠甘肃亚种[Cricetulus triton canus(Allen),1928]。     

甘肃仓鼠分类地位再讨论

作者在甘肃仓鼠(Cansumyscanus)模式标本产地附近的甘肃莲花山自然保护区采获甘肃仓鼠和大仓鼠(Cricetulustriton) ,通过比较标本发现二者在形态上存在显著差异,且甘肃仓鼠头骨的眶间深槽和耳外缘基部的白毛在仓鼠亚科中都是独特的,因此,建议恢复甘肃仓鼠属。陕西的甘肃仓鼠与莲花山的甘肃仓鼠虽有一定相似,但在尾部和头骨上存在明显差别,分类地位有待进一步研究。     

大仓鼠的核型与B染色体研究

采用骨髓细胞染色体制片法,对分布于山东济南、泰山、东北长白山和陕西西安的大仓鼠的染色体组型、Ｇ－带、Ｃ－带和银染核型进行了分析研究。济南、西安和长白山的标本的二倍体数目和核型相似,２ｎ＝２８,２２ｔ＋４ｍ＋ＸＹ（ｓｔ,ｍ）。泰山标本的二倍体数目为２ｎ＝２８～２９,即在６７５％的中期相中多出了一条形态最小的端着丝粒染色体,这条染色体为Ｂ染色体,可能起源于Ｘ染色体。泰山标本的Ａ染色体组与上述３地标本相同。４地标本的Ｇ－带、Ｃ－带和银染核型相似。除Ｂ染色体外,每个端着丝粒染色体都具有着丝粒异染色质,ＡｇＮＯＲｓ较恒定地出现在Ｎｏｓ２,４,８,９,１３染色体上。也就是说大仓鼠的Ｂ染色体为Ｃ－带阴性,不携带核仁组织者。这种Ｂ染色体Ｃ－带阴性的特征在赤狐、黑家鼠和大林姬鼠朝鲜亚种中亦有报道。     

甘肃仓鼠属 Cansumys 在河南的发现

甘肃仓鼠属Ｃａｎｓｕｍｙｓ在河南的发现路纪琪，王廷正（河南师范大学生物系新乡４５３００２）（陕西师范大学生物系）关键词甘肃仓鼠属，发现，河南作者在进行河南省啮齿动物调查时，于１９９４年６月在大别山区的商城县黄柏山（海拔３２０ｍ）和罗山县灵山寺（海拔４...     

准噶尔雅罗鱼染色体核型及带型的初步研究

以肾细胞作材料,采用秋水仙素-低渗-空气干燥法、Ag-NORs、C-带和G-带显带技术对准噶尔雅罗鱼(Leuciscus merzbacheri)染色体进行了研究。结果表明:(1)准噶尔雅罗鱼2n=50,核型组成为18m+14sm+6st+12t,NF=82,没有异型性染色体分化。(2)Ag-NORs的数目在不同的细胞中表现出多态性,数目为1～2个,出现1个Ag-NORs的频率最低(10%),出现2个的频率最高(70%);Ag-NORs主要出现在m1对和m4对同源染色体上;未发现有Ag-NORs联合的现象。(3)准噶尔雅罗鱼的染色体均呈现C-带阳性,可分为着丝粒C-带和端粒C-带。(4)同源染色体上G-带带纹基本一致,其带纹在每对染色体上的数目及分布具有明显特征性。     

福建大头蛙的核型及带型分析

利用骨髓细胞蒸气固定法制备染色体标本,研究了福建大头蛙(Limnonectesfujianensis)黄山居群的核型、C 带和Ag NORs。结果表明,福建大头蛙核型为2n =2 2 =2 0M 2SM ,NF =44,次缢痕位于No 1 0q ;各染色体均有着丝粒C 带,3p、9q出现插入型C 带;Ag NORs位于1 0q。     

黑斑蛙核型、C-带及Ag-NORs 研究

本文采用外周血淋巴细胞培养法制备染色体标本,观察黑斑蛙的染色体标本,研究黑斑蛙的核型,C-带和Ag-NORs。研究结果表明：（1）黑斑蛙淋巴细胞染色体数目为2n=26,其中有5对大染色体和8对小染色体,核型是二型性核型;（2）分别对雌雄个体的中期分裂相进行观察,在第11号染色体长臂中部有明显的次缢痕,但变异核型次缢痕在第8号染色体长臂的中部;（3）在第5号染色体长臂上有一条明显的近端粒C-带;（4）第11号染色体是一对具有银染核仁形成区的同源染色体,且雌雄个体的银染位置相同。     

葱小孢子的染色体和核型研究

 本文用胰酶-尿素双重处理法和SSG法,分别进行了葱小孢子染色体螺旋的诱导和染色体C-带的显带研究,首次成功地获得了葱小孢子染色体螺旋和染色体C-带,螺旋图象清晰;染色体C-带与体细胞的基本一致,所有染色体上均显示出明显的末端带,但未出现次缢痕带。另外,研究了葱小孢子的核型,其结果与体细胞的核型基本一致,但有差异。作者认为小孢子的核型比体细胞的核型准确,更能反映出葱的核型特征。     

纳特竖蟾(无尾目:滑背蟾科) 的细胞遗传、与相关属物种的核型相似性并兼论其分类地位

本文报道纳特竖蟾(Eupemphix nattereri Steindachner,1863)巴西3个产地标本的核型,均为2n=22,由1对端部和10对中或亚中部着丝点染色体组成.仅一对NORs位于No.11染色体对长臂端部,而其位置有别于常见的具有标志性意义的近着丝点位置.该NORs的位置为rDNA为探针的荧光原位杂交(FISH)所确认.各染色体对中,着丝点C-带明显,插入或端带偶见.某些标本的No.8同源染色体对间C-带的大小随异染色质化的程度不同而变化.居于较小的实验标本量,这种在3个产地的雌或雄性标本之一中观察到的C-带异型现象可能为种下细胞地理学变异,亦或为细胞学意义的性染体分化.3产地之一的标本核型的No.11着丝点C-带异染色质化的程度较高.CMA3染色检测到部分GC-rich区域,DAPI染色未显示任何AT-rich区.成功获得BrdU复制带,并将其与滑背蟾类动物(leiuperid)中近缘属及物种进行对比分析.比较结果表明,纳特竖蟾的核型与斑符泡蟾种组(Physalaemus signifer group)难以相互区别,而与肿肋蟾属(Pleurodema Tschudi,1838)极为相似.核型数据支持形态学上将纳特竖蟾、二光肿肋蟾[Pleurodema diplolister (Peters,1870)]和短头肿肋蟾[P.brachyops(Cope,1869)]划为同一分支的观点[动物学报 53(2):285-293,2007].     

赤链蛇染色体组型、C型和Ag—NORs的研究

以骨髓细胞为材料研究赤链蛇的染色体,结果表明该物种2n=46,由8对大型的和15对微小的染色体组成,AF＝50。性染色体的大小介于3号和4号之间,为ZW;8大型染色体均显示着丝粒C带,1－6号还显示浅染端粒C带。W染色体为整条C带阳性,该物种一对NOR位于7号染色体近着丝粒区。不同地理分布群赤链蛇核型可能经历过Z与W染色体不等交换。     

大蹄蝠的核型分析

研究了大蹄蝠的核型、C-带和Ag-NORs。大蹄蝠的染色体数目是2n=32,NF=60,No.8染色体上有一明显的次缢痕,大蹄蝠有丰富的结构异染色质,主要以着丝粒带的形式存在;且有若干对染色体部分或全部异染色质化;一对Ag-NORs稳定地出现于No.8染色体。     

Karyotype and genome size of Iberochondrostoma almacai (Teleostei, Cyprinidae) and comparison with the sister-species I.lusitanicum

This study aimed to define the karyotype of the recently described Iberian endemic Iberochondrostoma almacai, to revisit the previously documented chromosome polymorphisms of its sister species I.lusitanicum using C-, Ag-/CMA(3) and RE-banding, and to compare the two species genome sizes. A 2n = 50 karyotype (with the exception of a triploid I.lusitanicum specimen) and a corresponding haploid chromosome formula of 7M:15SM:3A (FN = 94) were found. Multiple NORs were observed in both species (in two submetacentric chromosome pairs, one of them clearly homologous) and a higher intra and interpopulational variability was evidenced in I.lusitanicum. Flow cytometry measurements of nuclear DNA content showed some significant differences in genome size both between and within species: the genome of I. almacai was smaller than that of I.lusitanicum (mean values 2.61 and 2.93 pg, respectively), which presented a clear interpopulational variability (mean values ranging from 2.72 to 3.00 pg). These data allowed the distinction of both taxa and confirmed the existence of two well differentiated groups within I. lusitanicum: one that includes the populations from the right bank of the Tejo and Samarra drainages, and another that reunites the southern populations. The peculiar differences between the two species, presently listed as "Critically Endangered", reinforced the importance of this study for future conservation plans.     

Karyotype analysis and DNA content in some species of Chrysolaena (Vernonieae,Asteraceae)

Cytogenetic characterization by karyotyping and determination of DNA content by flow cytometry of five species of Chrysolaena (Vernonieae, Asteraceae) was performed. This is the first study of nuclear DNA content realized in the genus. The 2C-values were compared with the ploidy level and the total karyotype length (TKL) of each species. Mitotic analysis revealed a base chromosome number x = 10 for all entities and different ploidy levels, from diploid (2n = 2x = 20) to octoploid (2n = 8x = 80). All species showed bimodal karyotypes composed of metacentric and submetacentric chromosomes. The average chromosome size (ML) varied from 1.86 μm to 2.70 μm, while the TKL ranged from 18.65 μm to 80.55 μm. The intrachromosomal asymmetry index (A₁) varied from 0.27 to 0.38, while the interchromosomal asymmetry index (A₂) ranged from 0.19 to 0.25. A new cytotype is reported for the first time for C. propinqua. Accessory chromosomes found in C. verbascifolia, C. cognata, C. flexuosa, and C. propinqua are also reported as new.     

Systematic relationships within the Microtus arvalis (Rodentia: Cricetidae) group in Iran,inferred from cytogenetic analyses

The distribution of C-heterochromatin and nucleolar organizer regions (NORs) was studied in three species of voles of the Microtus arvalis group in Iran: M. mystacinus, M. kermanensis, and M. transcaspicus. The C-banding pattern and NORs distribution were similar in M. mystacinus and M. kermanensis suggesting taxonomic proximity of these two species. At the same time, the karyotypes of M. mystacinus from Iran were different in C-banding pattern from the complements of conspecific 54-chromosome voles from Europe and other regions of Asia. The most distinct difference was in size of the distal C-positive block of heterochromatin on the X chromosome. In this respect M. mystacinus from Iran and M. kermanensis resembled M. transcaspicus. Small size of the distal C-positive heterochromatic block may be ancestral whereas larger size is derived. The X chromosome of M. transcaspicus can be derived from that of M. mystacinus and M. kermanensis by a large inversion or centromeric shift.     

Karyotype analysis in three species of the genus Chirostoma (Atheriniformes: Atherinidae)

Karyotype analyses of three Chirostoma species, C. estor, C. patzcuaro, and C. jordani from Mexico, are presented. C. estor and C. jordani have both a diploid number of 2N = 48 and a fundamental number of NF = 68, but different karyotype formulae. The co-occurrence of these karyotypes with morphometric and allozymatic primitive features so far reported suggests that the ancestral karyotype of the genus Chirostoma was similar to the one shown by these species. The divergent karyotype of C. patzcuaro (2N = 44 and NF = 44) could be related to its endemism and to the relatively small size of its populations. Received: February 7, 2001 / Revised: September 7, 2001 / Accepted: October 11, 2001     

The Karyotype Analysis of Somatic Chromosomes in Amborella trichopoda (Amborellaceae)

Amborella trichopoda Baill. (Amborellaceae), which, based on multiple gene analyses, was recently identified as the first branch in the angiosperm evolution, has somatic chromosomes of 2n=26 (x=13). At metaphase all the chromosomes have centromeres at the median position. Chromosomes of one pair are longer than those of the 12 remaining pairs, and have a secondary or small constriction. Based on karyotype analysis, as well as a survey of chromosome numbers in two other earliest lineages (i.e., Nymphaeaceae and Illiciales), the x=13 of Amborella is likely to be derived from x=14. The hypothesis that x=7 is the original base number in the angiosperms was briefly discussed. Received 30 May 2000/ Accepted in revised form 22 July 2000     

Variation in size and location of the Ag-NOR in the Atlantic halibut (<Emphasis Type="Italic">Hippoglossus hippoglossus</Emphasis>)

The distribution of differentially stained chromatin was studied in the Atlantic halibut (Hippoglossus hippoglossus) chromosomes (2n = 48). Four pairs of homologous chromosomes were identified using a combination of traditional cytogenetic staining techniques (Giemsa/DAPI/CMA3/Ag-NO3). Chromosome 1 showed a length polymorphism (1^S-short, 1^L-long isoforms of the chromosome 1) which was related to the variation of the size of the Ag-NORs. In one specimen the Ag-NOR was translocated from chromosome 1 into the telomeric region on the q-arm of the chromosome 2 forming a derivative chromosome der(2)t(1^S;2)(q?;q?). Four Ag-NOR genotypes have been shown: 1^S1^S, 1^S1^L, 1^L1^L and 1^S der(2)t(1^S;2)(q?;q?). The chromosome rearrangements did not leave any interstitially located telomeric sequences and the telomeres were confined to the ends of the chromosomes. A single chromosomal location of 5S rDNA clusters was found using the PRINS technique. In the extended metaphase spreads two adjacent clusters of 5S rDNA could be seen on one chromosome while condensed chromatin gave a single hybridization signal. Double 5S rDNA signals on the same chromosome arm suggested paracentric inversion of the minor rDNA site. 5S rDNA clusters were not co-localized with Ag-NORs. Although female and male karyotypes were compared no sex related cytogenetic markers were found.