Developments in avian cytotaxonomy: implications for Afro-avian Species

Ejere. VC. 2000. Developments in avian cytotaxonomy: implications for Afro-avian Species. Ostrich 71 (1 & 2): 40.

Karyological studies of the extant species of birds have progressed slower than those of other animal groups. To date, a paltry proportion of less than 20% of about an estimated 9 000 avian species have been karyotyped, such that for most orders, karyological information remains largely scanty. Data accumulated so far, has revealed a lot of interesting features of the typical avian karyotype. Essentially, the karyotype is dichotomous, containing several pairs of fairly big chromosomes (= macrochomosomes) and very small to minute chromosome elements (= microchromosmes). The diploid chromosome number is also variable, ranging from 2n = 40 to 2n = 92 with a mode of 2n = 80 chromosomes observed in a majority of species. Studies have further revealed that chromosomal evolution in birds is highly conservative especially with reference to the first 3 pairs of macrochromosomes. (Group A), while considerable variability in number and morphology occurs in the remaining groups of chromosome elements. These variabilities, as well as the homologies revealed by chromosome banding techniques, have aided the cytotaxonomy of various individual avian groups. In this review, the karyological as well as the phylogenetic relationships of the various avian species so far karyotyped, vis-a-vis the cytotaxonomic implications for the abundant Afro-avian fauna are highlighted. Similarly, the significance of the observed peculiarities in the avian karyotype is briefly discussed. Suggestions are proffered in respect of the application of karyotype analysis technique to bird conservation in Africa. This will focus mainly on the identification of the gender of birds for the singular purpose of breeding rare and endangered species for zoological gardens and related institutions.     

四种天牛的核型比较研究

为弄清天牛的核型特征, 补充我国天牛染色体分类特征和天牛细胞分类学的基础研究空缺, 本文以4种沟胫天牛亚科天牛为研究对象, 选取天牛的分裂旺盛组织精巢（卵巢）和中肠, 在不同的条件下进行天牛染色体玻片的制备和观察。结果显示： 4种天牛染色体数目均为 2n = 20, 性别决定机制为Xy_p。其中, 云斑白条天牛Batocera lineolata的核型公式： 4L+5M+Xy_p, 大型染色体4对, 中型染色体5对, 性染色体为小型; 榉白背粉天牛Olenecamptus cretaceus marginatus、 中华八星粉天牛Olenecamptus octopustulatus chinensis（粉天牛属）和桑天牛Apriona germari的核型公式均为： 5L+4M+Xy_p, 大型染色体5对, 中型染色体4对, 性染色体为中型。粉天牛属的榉白背粉天牛和中华八星粉天牛的核型指数非常相近; 桑天牛的染色体公式虽然与粉天牛属相同, 但长度和着丝粒位置明显不同。     

贵州产蜘蛛抱蛋属植物的细胞分类学研究

报道了6种贵州产蜘蛛抱蛋属植物的染色体数目和核型,并与其相应近缘种对比,联系植物的外部形态特征,探讨核型结构与形态特征的相关性.发现1个种的染色体数目为2n =36,5个种的染色体数目为2n =38,核型公式分别为:平塘蜘蛛抱蛋(Aspidistra pingtangensis),2n =38 =20m +4sm(2sat) +14st;荔波蜘蛛抱蛋(A.liboensis),2n =38 =22m(2sat)+4sm+ 12st;赤水蜘蛛抱蛋(A.chishuiensis),2n =38 =22m(2sat)+8sm +8st;伞柱蜘蛛抱蛋(A.fungilliformis),2n =36=18m (2sat) +4sm+ 14st;四川蜘蛛抱蛋(A.sichuanensis),2n =38 =22m (2sat) +4sm +12st;丛生蜘蛛抱蛋(A caespitosa),2n =38 =20m +6sm(2sat) +12st.核型类型都为2C型.其中平塘蜘蛛抱蛋、荔波蜘蛛抱蛋和赤水蜘蛛抱蛋的染色体数目和核型均为首次报道.研究结果表明,该属植物的核型结构与外部形态特征具有一定的相关性,细胞分类学研究可以为该属植物起源进化研究以及自然分类鉴定提供一定的依据.     

Cytoevolution, Phylogeny and Taxonomy in Epacridaceae

Chromosome numbers in Epacridaceae were collated from variousauthors and superimposed on to recent cladograms for the family.The results strongly indicate that reduction in chromosome numberoccurs with evolutionary advancement. Thus Epacridaceae, incommon with ‘Ericaceaesens. strict .’ and ‘Vacciniaceaesens.strict. ’, has evolved from a primitive karyotype of atleastx =12 and probablyx =13. This conclusion dispels earlierpaleopolyploid models based on a primitivex =6 in the family.Other aspects of cytoevolution, such as chromosome number asa generic character especially in cytologically advanced generaof the Styphelieae, are discussed. Cytoevolution; cladistic models; primitive character states for chromosome number; dysploid falls; cytotaxonomy; Epacridaceae; Richeoideae; Epacridoideae; Epacrideae; Styphelieae; Ericaceae     

昆虫细胞分类学的基本问题及染色体系统发育的重建方法

本文非昆虫细胞遗传学及细胞分类学原理与技术的全面评述;而是从细胞遗传学特征（或称染色体特征）在混虫分类学中的应用入手,重点提出与分析了昆虫细胞分类学中的种类鉴定,研究取材,染色体多态现象,多倍体及核型进化方向等基本问题,并着重总结了目前国际上细胞水平染色体数据的处理方法,即传统法,倒位法,数值法与支序法;最后,作者指出了正确看待细胞分类学重要性的态度。     

“x” is not a bias,but a number with real biological significance

Recent literature criticized the use of the symbol “x” to denote basic chromosome number in cytotaxonomy. I show here that this criticism is superfluous and is based on historical confusion between the concepts of basic chromosome number (or monoploid chromosome number), which is objective, and ancestral basic chromosome number, which is always inferred, by means of several – more or less reliable – methods. The most relevant literature is discussed and, in the end, I propose the use of x for basic chromosome number and p for (hypothetical) ancestral basic chromosome number.     

The evolutionary origin of a novel karyotype in Timarcha (Coleoptera, Chrysomelidae) and general trends of chromosome evolution in the genus

In this work, we have analysed the karyotypes of six species of Timarcha for the first time and updated the cytological information for two additional taxa, for one of them confirming previous results ( Timarcha erosa vermiculata ), but not for the other ( T. scabripennis ). We describe the remarkable karyotype of T. aurichalcea , the lowest chromosome number in the genus (2 n  = 18), distinctive as well for the presence of an unusual chiasmatic sexual bivalent hitherto unreported for Timarcha . This study increases the number of species studied cytologically in this genus to forty. Additional cytogenetic analyses are performed on several species, including Ag-NOR staining and fluorescent in situ hybridization (FISH) studies with ribosomal DNA probes. Karyotype evolution is analysed by tracing different karyotype coding strategies on a published independent phylogenetic hypothesis for Timarcha based on the study of three genetic markers. The implementation of a likelihood model of character change optimized onto the phylogeny is tentatively used to detect possible drifts in chromosome changes. These analyses show that karyotype is conservative in the evolution of the genus and that there is an apparent trend to reducing chromosome number. Cytological and phylogenetic data are used to explain the evolutionary origin of the karyotype of T. aurichalcea by two centric fusions involving one pair of acrocentric autosomes and the sexual chromosomes.     

Re-evaluation of HeLa, HeLa S3, and HEp-2 karyotypes

In contrast to earlier reports, this study on HeLa, HeLa S3, and HEp-2 revealed that karyotypes of each cell line are characterized by a consistent marker chromosome composition and a constant number of copies for both normal and marker chromosomes. Based on these chromosome fingerprints and an analysis of 50 metaphases, the modal karyotype of each cell line was defined. Each modal karyotype had the composite content of the previously reported karyotypes of the same cell line, and, generally, the former had the same or a higher number of copies per chromosome than the latter. This modal karyotype can be used as a standard to identify and further individualize both the cell line itself and a subline within that cell line. We have also found that many cells within each cell line have the same karyotype. Portions of numerical data are compiled in a chart format by which the extent of chromosome differences between cultures can readily be compared. Also discussed in brief are characteristic chromosome changes that may help distinguish clonally derived cell lines from lines derived by cross-contamination.     

Questions of procedure in moss cytotaxonomy: new data for some British species

Abstract

Cytological data for Gymnostomum aeruginosum (n = 13), Discelium nudum (n = 13) and Plagiomnium ellipticum (n = 6) supplement earlier records from Britain and elsewhere but those for Physcomitrium sphaericum (n = 26) are the first for the species. Chromosome counts continue to have a role to play in bryophyte cytotaxonomy as a means of identifying probable erroneous reports. It is considered, however, that karyotype definition in terms of Giemsa C-banding and cytogenetic studies related to chromosome behaviour have greater taxonomic potential.     

Chromosome numbers in the Aphididae and their taxonomic significance

Abstract. Diploid female chromosome numbers are listed for 180 aphid species not previously karyotyped. The list includes the first chromosome records for several aphid tribes (Tramini, Greenideini, Anomalaphidini, Nippon-aphidini). Variation in chromosome number at different systematic levels is discussed. Usually the karyotype is particularly stable within a genus, but there are notable exceptions (e.g. Amphorophora ) where considerable evolutionary increase in chromosome number has occurred by autosome dissociation with little accompanying morphological change. In several genera differences in gross chromosome morphology can be useful to the taxonomist. Within-species karyotype variation is relatively common in aphids, and instances of structural heterozygosity are particularly numerous in species and groups which have partially or completely abandoned the sexual phase of the life cycle in favour of permanent thelytoky.     

染色体数据的挖掘及其在植物多样性进化研究中的利用

多倍化（或全基因组加倍）是植物物种形成的重要途径,现存的被子植物可能都发生过一次甚至多次多倍化事件。多倍化传统的定义是染色体数目相对于祖先类群呈整倍性增加。其中最常用的研究方法是核型分析,核型能够提供物种的基本细胞学参数,包括染色体数目、倍性水平、核型不对称性、核型变异系数等。目前核型研究的趋势表现出从物种基本核型参数分析逐渐演化到多类群、多学科交叉融合的特点：一方面植物核型分析从种群、物种、科属的类群到生命之树,探讨染色体核型在各支系的进化特征、趋势以及驱动植物系统进化的细胞学机制;另一方面探讨和分析区域或生态系统植物区系的染色体谱或倍性等细胞学特征,可以探究区域地质环境变化或生态环境对染色体倍性等的影响,或通过区域染色体谱的构建,分析区域植物区系的形成和进化历史。因而,植物核型研究为系统发育、分子系统进化、生命之树以及植物区系地理的起源和演化研究提供了新思路。越来越多的新方法、新手段在植物核型分析与多倍化研究中得到运用,从而揭示了植物类群或植物区系的染色体进化以及细胞地理特征。今后植物细胞学研究趋势会向多学科交叉融合,整合各研究领域证据,从不同水平角度综合分析植物核型多样性形成的原因及意义,从而更加全面地认识和理解植物物种多样化与物种形成原因。     

染色体数据的挖掘及其在植物多样性进化研究中的利用

多倍化(或全基因组加倍)是植物物种形成的重要途径,现存的被子植物可能都发生过一次甚至多次多倍化事件。多倍化传统的定义是染色体数目相对于祖先类群呈整倍性增加。其中最常用的研究方法是核型分析,核型能够提供物种的基本细胞学参数,包括染色体数目、倍性水平、核型不对称性、核型变异系数等。目前核型研究的趋势表现出从物种基本核型参数分析逐渐演化到多类群、多学科交叉融合的特点:一方面植物核型分析从种群、物种、科属的类群到生命之树,探讨染色体核型在各支系的进化特征、趋势以及驱动植物系统进化的细胞学机制;另一方面探讨和分析区域或生态系统植物区系的染色体谱或倍性等细胞学特征,可以探究区域地质环境变化或生态环境对染色体倍性等的影响,或通过区域染色体谱的构建,分析区域植物区系的形成和进化历史。因而,植物核型研究为系统发育、分子系统进化、生命之树以及植物区系地理的起源和演化研究提供了新思路。越来越多的新方法、新手段在植物核型分析与多倍化研究中得到运用,从而揭示了植物类群或植物区系的染色体进化以及细胞地理特征。今后植物细胞学研究趋势会向多学科交叉融合,整合各研究领域证据,从不同水平角度综合分析植物核型多样性形成的原因及意义,从而更加全面地认识和理解植物物种多样化与物种形成原因。     

Karyomorphology and GC-rich heterochromatin pattern in Passiflora (Passifloraceae) wild species from Decaloba and Passiflora subgenera

Thirteen wild species of Passiflora were analyzed using conventional and CMA/DA/DAPI staining to evaluate the karyotype diversity between and within the subgenus Decaloba and Passiflora. The karyotypic features indicate that both subgenera have a conserved chromosome number, as reported before for several species. Submetacentric (sm) chromosomes were found in species from both subgenera, suggesting that sm chromosomes are not restricted to a particular subgenus. The analysis of the karyotypic heterogeneity enabled to distribute the species in three groups, but with no support to phylogenetic and taxonomic levels. The application of fluorochromes allowed for the visualization of CMA⁺/DAPI⁻ blocks, which in our studies always correlated with the occurrence of satellites, showing that occurrence of two chromosome pairs with satellites per cell is a characteristic shared by some species from both subgenera. This feature does not always have relationship with the basic chromosome number. The data found in this study will help to understand the phylogeny, cytotaxonomy, and evolution of the genus Passiflora showing that karyotypic variation can be seen between and within the subgenus Decaloba and Passiflora.     

多花水仙(Narcissus tozetta L.)染色体基数x=10和X=11之间进化关系的研究

多花水仙的染色体基数有x=10和x=11两类。基数x=10组型有两种,一种是具6长、4短的典型不对称的二形染色体组型;另一种是具有4长、2中、4短(或5长、2中、3短)的非二形染色体组型。基数x=11则具有4长、2中、5短(或5长、2中、4短)的非二型或非典型二形的染色体组型。x=10的典型不对称的二形染色体组型是原始的组型。基数x=11是从原始的x=10、2n=20组型中的(第5、6号)染色体发生不等长易位后,增加了一对短小的中着丝粒染色体而形成的。另一个x=10、2n=20的非二型新组型,可能从x=11组型丢失了短小的中着丝粒染色体衍生而来,也可能从易位后的个体所产生的不含中着丝粒染色体的雌、雄n配子结合而得到。     

我国直翅目昆虫细胞分类学研究现状

从研究材料、研究方法、染色体研究在昆虫分类上的应用 3个方面对我国昆虫尤其是直翅目昆虫的细胞分类学研究情况作了简要的概述 ,并着重论述了直翅目昆虫的核型及带型的研究现状 ,同时对我国直翅目昆虫分类学的发展前景进行了展望     

Molecular cytogenetic analysis and the establishment of a cell culture in the fish species Hollandichthys multifasciatus (Eigenmann & Norris, 1900) (Characiformes,Characidae)

Hollandichthys is a fish genus of the family Characidae that was until recently considered to be monotypic, with cytogenetic, morphological, and molecular data being restricted to a few local populations. In the present study, the karyotype of a population of Hollandichthys multifasciatus was analyzed using classical and molecular cytogenetic approaches for the investigation of potential markers that could provide new perspectives on the cytotaxonomy. H. multifasciatus presented a diploid number of 2n=50 chromosomes and a karyotype formula of 8m+10sm+32st. A single pair of chromosomes presented Ag-NORs signals, which coincided with the 18S rDNA sites visualized by FISH, whilst the 5S rDNA sequences were mapped in two chromosome pairs. The distribution of the U snRNA genes was mapped on the Hollandichthys chromosomes for the first time, with the probes revealing the presence of the U1 snDNA on the chromosomes of pair 20, U2 on pairs 6 and 19, U4 on pair 16, and U6 on the chromosomes of pair 11. The results of the present study indicated karyotypic differences in comparison with the other populations of H. multifasciatus studied previously, reinforcing the need for further research to identify isolated populations or the potential existence of cryptic Hollandichthys species.     

Polymorphism and divergence of karyotypes in taimens of the Hucho genus

Karyotypes of Siberian taimen Hugo taimen from the Manoma River (Amur basin) were investigated. The karyotypes examined differed in chromosome number from 2n = 82 to 2n = 83; chromosome arm number was NF = 112. These differences, as well as the difference in the karyotype of Siberian taimen from the lower flow of the Amur River (2n = 84) described earlier, are due to Robertsonian polymorphism of one pair of large submetacentric chromosomes. The nucleolus organizer regions are located on the short arms of one or two subtelocentric chromosomes of different pairs. The probable sequence of karyotype divergence in taimens of the Hugo genus is discussed.     

基于比较核型分析方法追溯百合族 (百合科) 二型性核型的起源

百合族具有非常一致的二型性核型,由4条长染色体以及20条短染色体组成。目前有两个假说解释其二型性核型的来源,着丝粒横裂和多倍化。但是,具体是哪一种机制起主要作用仍然不清楚。根据文献以及自己的实验结果,我们整理并重新分析了百合亚科和美德兰亚科所有属的核型资料。比较核型分析结果表明,来自单条染色体的特征、染色体臂数、核型不对称性以及染色体的相对长度诸方面的证据都支持着丝粒横列是百合族核型进化的主要机制,但不能排除其它的机制也在起着作用,如臂间倒位和易位。臂间倒位和易位可能在郁金香族的核型进化中起着主要的作用。另外,本研究还报道了三个种的核型,粗茎贝母 (Fritillaria crassicaulis)、准格尔郁金香 (Tulipa suaveolens) 和尖果洼瓣花 (Gagea oxycarpa)。     

不同地理区域鲫鱼染色体银染核仁组织者的比较研究

本文对不同地理区域的鲫鱼(Carassius auratus)—滇池高背鲫、低背鲫、方正银鲫(C.auratusgibelio)的核型及核仁组织者NORs进行了比较研究,并对高背鲫来源作些初步探讨,结果如下: 1.低背鲫Carassius auratus (back low type):2n=100,22m+30sm+48t.st,NORs=4,出现于第5—6对亚中着丝粒染色体短臂。 2.滇池高背鲫Carassius auratus(back high type):2n=156,30m+46sm+80t.st,NORs=6,出现于第5—7对亚中着丝粒染色体短臂。 3.方正银鲫C.auratus gibelio:2n=162,32m+52sm+78t.st NORs=4,出现于第5—6对亚中着粒染色体短臂。