Occurrence of macro B chromosomes in Astyanax scabripinnis paranae (Pisces,Characiformes, Characidae)

B chromosomes occur in several Neotropical fish species. Cytogenetic analysis of 27 specimens (15 females and 12 males) of Astyanax scabripinnis paranae from the Araquá river (a small headwater tributary of the Tietê river) shows that this population has 2n=50 chromosomes (4M+30 SM+4ST+12A), two chromosome pairs with NORs and conspicuous C-band positive blocks in the terminal position of the long arm of four chromosome pairs. In this population, eight females presented 2n=51 chromosomes and the extra chromosome was a large metacentric similar in size and morphology to the first chromosome pair in the karotype. This accessory chromosome is entirely heterochromatic in C-banded metaphases and shows a late replication pattern evidenced by BrdU incorporation. There was no significant correlation between the presence of B chromosomes and increased NOR activity at the P>0.05 level. Some aspects related to these B chromosomes are discussed.     

An X1X1X2X2/X1X2Y mechanism of sex determination in a South American rodent, Deltamys kempi (Rodentia, Cricetidae)

Chromosome studies on 14 specimens of Deltamys kempi disclosed six males with 2n = 37, NF = 38, six females with 2n = 38, NF = 38, and two females with 2n = 37, NF = 38. G- and C-band analyses revealed a Y-autosome translocation in the males leading to a multiple chromosome system of sex determination of the type X1X1X2X2/X1X2Y, this being the second case of such a mechanism described in rodents. At meiosis the males presented a trivalent in which C-banding studies showed an alternate orientation of the sex chromosomes due to end-to-end association of the X1 and Y chromosomes, the Y and the X2 being held together by interstitial chiasmata. At metaphase II both n = 17 + Y and n = 18 + X1 are regularly observed. The two females with 2n = 37, NF = 38, are heterozygous for an autosomal centric fusion involving chromosomes 1 and 13. The product of the Y-autosome translocation constitutes the largest element of the karyotype (9.4% of the haploid set); the X1 chromosome amounts to 7.8% of this set, including a large heterochromatic block. When only its euchromatic region is considered, this percentage decreases to 4.6%. From two to seven NORs were observed at the telomeres, with a mean of 4.4 +/- 1.1 per cell.     

Occurrence of multiple sexual chromosomes (XX/XY1Y2 and Z1Z1Z2Z2/Z1Z2W1W2) in catfishes of the genus Ancistrus (Siluriformes: Loricariidae) from the Amazon basin

Loricariid catfishes show a predominance of homomorphism in sex chromosomes, but cases of simple and multiple systems were also found. Here we describe two cases of multiple sex chromosome systems in loricariids from Brazilian Amazonia. Males of Ancistrus sp.1 "Balbina" have a modal number of 2n = 39 chromosomes, fundamental number (FN) of 78, and karyotypic formula of 27 m + 10 sm + 2 st; females have 2n = 38 chromosomes, FN = 76, and 26 m + 10 sm + 2 st. Ancistrus sp.2 "Barcelos" has 2n = 52 chromosomes for both sexes, FN = 80 for males and FN = 79 for females. Karyotypic formula is 12 m + 12 sm + 4 st + 24a for males and 11 m + 12 sm + 4st + 25a for females. The two species show different arrangements of constitutive heterochromatin blocks, which are coincident with NORs and absent in sex chromosomes. We suggest a XX/XY(1)Y(2) mechanism for Ancistrus sp.1 "Balbina", and a Z(1)Z(1)Z(2)Z(2)/Z(1)Z(2)W(1)W(2) mechanism for Ancistrus sp.2 "Barcelos". The XX/XY(1)Y(2) mechanism here reported is the second known occurrence of this type of multiple sex chromosomes for Loricariidae and the third for Neotropical fishes; the mechanism Z(1)Z(1)Z(2)Z(2)/Z(1)Z(2)W(1)W(2) represents the first record among fishes. The presence of different sex chromosome systems in Ancistrus indicates a probable independent origin and suggests that the differentiation of sex chromosomes is evolutionarily recent among species in this genus.     

Cytogenetic analysis and description of the sexual chromosome determination system ZZ/ZW of species of the fish genus Serrapinnus (Characidae, Cheirodontinae)

Four populations of Serrapinnus notomelas and one population of Serrapinnus sp.1, both belonging to the subfamily Cheirodontinae, were analyzed by Giemsa and silver nitrate impregnation techniques. We found 2n = 52 chromosomes for all populations, with interspecific differences in the karyotype formula; S. notomelas showed 16 m + 22 sm + 10 st + 4a, with fundamental number (FN) = 100 for males, and 16 m + 23 sm + 10 st + 3a, with FN = 101 for females. Serrapinnus sp.1 had 8m + 16 sm + 4 st + 24 a, with FN = 80 for males, and 8m + 15 sm + 4 st + 25 a, with FN = 79 for females. The difference in FN for the two sexes is due to a pair of heteromorphic chromosomes in the females of both species, which characterizes a ZZ/ZW-type mechanism of chromosome sexual determination. Interspecies differences were also found in nucleolus organizer regions (NORs). A simple NOR system was detected in three of four S. notomelas populations, while Serrapinnus sp.1 had two chromosome pairs with NOR. Although S. notomelas and Serrapinnus sp.1 have the same diploid number, differences in the karyotype structure indicate that these are different species. Apparently there was pericentric inversion during the karyotype evolution of these species.     

Chromosome inheritance in triploid Pacific oyster Crassostrea gigas Thunberg

Reproduction and chromosome inheritance in triploid Pacific oyster (Crassostrea gigas Thunberg) were studied in diploid female x triploid male (DT) and reciprocal (TD) crosses. Relative fecundity of triploid females was 13.4% of normal diploids. Cumulative survival from fertilized eggs to spat stage was 0.007% for DT crosses and 0.314% for TD crosses. Chromosome number analysis was conducted on surviving progeny from DT and TD crosses at 1 and 4 years of age. At Year 1, oysters from DT crosses consisted of 15% diploids (2n=20) and 85% aneuploids. In contrast, oysters from TD crosses consisted of 57.2% diploids, 30.9% triploids (3n=30) and only 11.9% aneuploids, suggesting that triploid females produced more euploid gametes and viable progeny than triploid males. Viable aneuploid chromosome numbers included 2n+1, 2n+2, 2n+3, 3n-2 and 3n-1. There was little change over time in the overall frequency of diploids, triploids and aneuploids. Among aneuploids, oysters with 2n+3 and 3n-2 chromosomes were observed at Year 1, but absent at Year 4. Triploid progeny were significantly larger than diploids by 79% in whole body weight and 98% in meat weight at 4 years of age. Aneuploids were significantly smaller than normal diploids. This study suggests that triploid Pacific oyster is not completely sterile and cannot offer complete containment of cultured populations.     

Cytogenetic analysis of the neotropical spider Nephilengys cruentata (Araneomorphae, Tetragnathidae): standard staining nors, C-bands and base-specific fluorochromes.

The aim of this work is to characterize Nephilengys cruentata in relation to the diploid number, chromosome morphology, type of sex determination chromosome system, chromosomes bearing the Nucleolar Organizer Regions (NORs), C-banding pattern, and AT or GC repetitive sequences. The chromosome preparations were submitted to standard staining (Giemsa), NOR silver impregnation, C-banding technique, and base-specific fluorochrome staining. The analysis of the cells showed 2n = 24 and 2n = 26 chromosomes in the embryos, and 2n = 26 in the ovarian cells, being all the chromosomes acrocentric. The long arm of the pairs 1, 2 and 3 showed an extensive negative heteropycnotic area when the mitotic metaphases were stained with Giemsa. The sexual chromosomes did not show differential characteristics that allowed to distinguish them from the other chromosomes of the complement. Considering the diploid numbers found in N. cruentata and the prevalence of X1X2 sex determination chromosome system in Tetragnathidae, N. cruentata seems to possess 2n = 24 = 22 + X1X2 in the males, and 2n = 26 = 22 + X1X1X2X2 in the females. The pairs 1, 2 and 3 showed NORs which are coincident with the negative heteropycnotic patterns. Using the C-banding technique, the pericentromeric region of the chromosomes revealed small quantity or even absence of constitutive heterochromatin, differing of the C-banding pattern described in other species of spiders. In N. cruentata the fluorochromes DAPI/DA, DAPI/MM and CMA3/DA revealed that the constitutive heterochromatin is rich in AT bases and the NORs possess repetitive sequences of GC bases.     

杂交鳢(斑鳢 ♀ ×乌鳢 ♂ )及其自交后代细胞核型初步分析

对杂交鳢(斑鳢♀×乌鳢♂)(Channa maculata ♀×C.argus ♂)及其自交后代的细胞核型进行了初步分析.结果表明,杂交鳢染色体数目为2n=45,核型公式为3m+4sm+6st+32t,染色体臂数(NF)为52;杂交鳢自繁后代群体存在两种染色体核型,一是染色体数目为45,核型公式为3m+4sm+6st+...     

风毛菊属5种植物的核型分析

采用常规压片法,对风毛菊属(Saussurea)5种植物的染色体数目和核型类型进行分析。结果表明:大耳叶风毛菊(S.macrota)核型公式为2n=2x=26=10m+12sm+4st,属2A型;长梗风毛菊(S.dolichopoda)核型公式为2n=2x=26=14m+8sm+4st,属2A型;川陕风毛菊(S.licentiana)核型公式为2n=2x=28=12m+16sm,属2B型;杨叶风毛菊(S.populifolia)核型公式为2n=2x=28=6m+18sm+4st,属2B型;尾叶风毛菊(S.caudata)核型公式为2n=2x=30=14m+14sm+2st,属2A型。这5种风毛菊属植物中,除大耳叶风毛菊染色体数目和核型类型与前人报道的一致外,其余4种植物的染色体数目和核型类型均为首次报道,并在川陕风毛菊中发现1对B染色体。     

角堇与大花三色堇染色体核型分析

以2份角堇与4份大花三色堇自交系为试验材料,采用染色体常规压片方法,观察和分析了它们的细胞染色体数目、相对长度、平均臂比等核型指标,以明确两种植物细胞学特点,为分类以及育种提供理论依据。结果表明:(1)2份角堇自交系染色体数目均为2n=2x=26,染色体基数为x=13,染色体核型公式分别为2n=2x=26=8m+12sm+6st、2n=2x=26=4m+16sm+6st,核型不对称系数为67.20%~70.10%,核型分类均属于3B。(2)4份大花三色堇自交系均为四倍体,其中2份(EYO-1-2-1-4、DSRFY-1-1-2)染色体数目为44,核型公式为2n=4x=44=4m+16sm+6st、2n=4x=44=16m+24sm+4st;2份(G10-1-3-1-4、XXL-YB-1-1-1-1)染色体数目为48,核型公式分别为2n=4x=48=8m+20sm+20st、2n=4x=48=4m+36sm+8st,核型不对称系数为66.74%~71.77%,核型分类属于2B、3B。     

First report of chromosome numbers and karyotypes of two monotypic genera endemic to eastern Asia: Brachystemma (Caryophyllaceae) and Craspedolobium (Fabaceae)

The chromosome numbers and karyotypes of Brachystemma and Craspedolobium, two monotypic genera endemic to eastern Asia, are reported here for the first time. The somatic chromosome numbers are 2n=40 for Brachystemma calycinum and 2n=22 for Craspedolobium unijugum. A karyotype of 2n=2x=40=28m+12sm was found in B. calycinum and that of 2n=2x=22=12m+10sm in C. unijugum, both of them have a moderately symmetrical karyotype type 2B and small‐sized chromosomes. Brachystemma has a unique basic chromosome number in Alsinoideae, which may support its isolated taxonomic position. As do some morphological characters, the basic chromosome number x=11 suggests that Craspedolobium belongs in the Millettioid clade.     

Cytogenetics of an unstable trisomie in barley (Hordeum vulgare).

The origin, identification, meiotic chromosome behavior, and breeding behavior of an unstable trisomic barley were studied. The extra chromosome originated by breakage and fusion of an acrocentric chromosome 3 in a plant from an F2 population of a cross between acrotrisomic 3L3S (2n = 14 + 1 acro3L3S) and a balanced lethal stock, xc. (xantha) ac (albino). The F2 population segregated only for the albino trait. The genotypic constitution of the trisomic plant was ac ac (for both normal chromosome 3) and Ac (for the unstable metacentric chromosome). The unstable extra metacentric chromosome was designated as metacentric 3B (abbreviated as meta3B). Meiotic chromosome behavior in plants with 2n = 14 + 1 meta3B differed from plant to plant and within spikes. Some plants showed only trisomic cells with a chromosome configuration of 1 III + 6 II and 7 II + 1 I at metaphase I, whereas other plants showed both trisomie and disomic cells (7 II) that resulted from the elimination of the extra meta3B. The frequency of ring trivalents was low (6.8%). An average transmission rate of unstable meta3B ranged from 4.3 to 12.9%. The elimination of meta3B, and hence loss of the dominant Ac allele, resulted in albino seedlings as well as white stripes on plants, leaves, and spikes. Chromosome numbers of albino seedlings in the progeny of 2n = 14 + 1 meta3B were all diploid (2n = 14), while green seedlings contained 2n = 14 + 1 meta3B. However, progenies of some spikes of one trisomic plant showed a low frequency of green diploids and metatrisomics (2n = 14 + 1 meta3B), which was attributed to crossing-over.     

青海四种雏蝗染色体核型的比较分析

采用常规染色体制片方法对雏蝗属的褐色雏蝗Chorthippusbrunneus(Thunb .) ,异色雏蝗C .big uttulus(Linnaeus) ,小翅雏蝗C .fallax(Zub .) ,青藏雏蝗C .qingzangensis(Ying)的染色体核型进行分析 ,结果 :染色体数目均为 2n(♂ ) =1 7=1 6+XO ;常染色体类型为两类 ,中着丝点染色体 (m ,6条 )和端着丝点染色体 (T ,1 0条 ) ;性染色体类型为端着丝点。褐色雏蝗、异色雏蝗和青藏雏蝗的核型公式和染色体的相对长度组成为K( 2n ,♂ ) =1 7=6m +1 1T =6L +6M +4S +XO ,K( 2n ,♀ ) =1 8=6m +1 2T =6L +6M +4S +XX ;小翅雏蝗的为K( 2n,♂ ) =1 7=6m +1 1T =6L +4M +6S +XO ,K( 2n ,♀ ) =1 8=6m +1 2T =6L +4M +6S+XX。褐色雏蝗性染色体中部有次缢痕。染色体臂数 4种均为NF =2 3(♂ ) ,2 4 (♀ )。     

山东10种植物的核型分析

对山东１０ 种植物进行了核型分析。茴茴蒜（ Ｒａｎｕｎｃｕｌｕｓｃｈｉｎｅｎｓｉｓ Ｂｇｅ－） 染色体数目２ｎ ＝１６ , 核型公式Ｋ（２ｎ） ＝ ２ｘ ＝ １６ ＝ ２ Ｍ ＋ ２ｍ ＋ ２ｓｍ ＋ １０ｓｔ, “３Ａ”类型; 五脉地椒（ Ｔｈｙｍｕｓｑｕｉｎｑｕｅｃｏｓｔａｔｕｓ Ｃｅｌａｋ－） 染色体数目２ｎ＝ ２６ , 核型公式Ｋ （２ｎ） ＝ ２ｘ＝ ２６ ＝ ８ Ｍ ＋ １８ｍ , “１Ａ”类型; 蛇床（ Ｃｎｉｄｉｕｍ ｍｏｎｎｉｅｒｉ（Ｌ－） Ｃｕｓｓ－） 染色体数目２ｎ＝ ２０ , 核型公式Ｋ （２ｎ） ＝ ２ｘ＝ ２０ ＝ ２Ｍ＋ １６ｍ ＋ ２ｓｍ , “２Ｂ”类型; 波斯菊（ Ｃｏｓｍｏｓ ｂｉｐｉｎｎａｔｕｓ Ｃａｖ－） 染色体数目２ｎ ＝ ２４ , 核型公式Ｋ（２ｎ） ＝ ２ｘ ＝ ２４ ＝ １６ｍ ＋ ２ｍ （ｓａｔ） ＋ ６ｓｍ , “２Ａ”类型; 白车轴草（ Ｔｒｉｆｏｌｉｕｍ ｒｅｐｅｎｓ Ｌ－） 染色体数目２ｎ＝ ３２ , 核型公式Ｋ （２ｎ） ＝ ４ｘ ＝ ３２ ＝ ３２ｍ , “１Ａ”类型; 铁苋菜（ Ａｃａｌｙｐｈａ ａｕｓｔｒａｌｉｓ Ｌ－）染色体数目２ｎ ＝ ３２ , 核型公式Ｋ （２ｎ） ＝ ２ｘ＝ ３２ ＝ ３２ｍ , “１Ｂ”类型; 地构叶（ Ｓｐｅｒａｎｓｋｉａ ｔ?     

黄芪属六种植物的核型多样性

采用常规压片法,对豆科黄芪属6种植物制备染色体标本进行核型分析。结果表明:体细胞中期染色体数目分别为:沙打旺、斜茎黄芪、达乌里黄芪2n=16,均为二倍体;草木樨状黄芪2n=32,为四倍体;紫云英、鹰嘴紫云英则呈现多数目性,紫云英染色体数变动范围为55～65,64条稍多,鹰嘴紫云英染色体数变动范围51～65,62条稍多,均为混倍体。核型公式分别为:沙打旺2n=2x=16=12m+4sm;斜茎黄芪2n=2x=16=10m+6sm;达乌里黄芪2n=2x=16=16m;草木樨状黄芪2n=4x=32=32m;紫云英2n=64=62m+2sm;鹰嘴紫云英2n=62=12M+50m(2SAT)。染色体核型呈现多样性。     

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).     

黄鳝体内寄生胃瘤线虫的染色体核型及G-带分析

采用常规空气干燥法制片,对寄生于黄鳝(Monopterus albus)体腔内的胃瘤线虫(Eustrongylidesignotus)染色体核型进行分析。结果表明:胃瘤线虫体细胞有12条染色体,为二倍体,核型公式为2n=12=10 m+2 sm。由5对常染色体和1对性染色体组成,性别决定模式为XX-XY,其中X、Y和1～4号染色体都为中着丝粒染色体,5号为亚中着丝粒染色体。每对染色体都有特定的G-带带型。     

Karyotypes of Bembidion quadrimaculatum (L.) and Clivina fossor (L.) (Coleoptera: Carabidae)

Bembidion quadrimaculatum possesses 24 chromosomes: 2n male = 22 + XY, 2n female = 22 + XX; their structure is meta- and submetacentric and differences in length between them are slight. Achiasmatic meiosis has been identified in spermatogenesis. The diploid chromosome number in Clivina fossor is 44; 2n male = 42 + XY, 2n female = 42 + XX. The chromosome structure is meta-, submeta-, and subtelocentric and X is the longest element in the set. 1 to 2 chiasmata per bivalent occur in meiosis.     

凤仙花近缘种间核型分析与叶表皮微形态研究

为探究凤仙花近缘种植物的细胞学和微形态学方面的亲缘关系,该文选取荔波凤仙花(Impatiens liboensis)及近缘种赤水凤仙花(I.chishuiensis)和管茎凤仙花(I.tubulosa)的根尖和叶表皮为实验材料,采用体细胞染色体常规压片法和叶表皮光学显微镜观察法对凤仙花近缘种植物进行染色体及叶表皮特征研...     

Protostrongylus rufescens: a cytogenetic study

The diploid chromosome number of Protostrongylus rufescens is 2n = 11 for males and 2n = 12 for females. So, the sex determinism mechanism is XO/XX. The study of the genetic behaviour of this species has been made. In diakinesis stage the bivalents show typical tetrads with cross, phi, and lineal configurations. The division of the sexual chromosome is prereductional for the first meiotic division.     

毛百合根尖染色体Giemsa C-带分析

本研究利用Giemsa C-带方法对毛百合(Lilium dahuricum Ker-Gawl)根尖染色体进行了分析。研究结果表明毛百合试管苗的染色体倍性变异丰富,染色体倍性变异包括二倍体(2n=2×=24)、三倍体(2n=3×=36)、四倍体(2n=4×=48)到六倍体(2n=6×=72)。对二倍体毛百合的C-带结果进行分析,其带型公式为:2n=2×=24=2CI++2CI+T+T++6I+2I++2I++2I+T++2I+T++2I+T++2T++2T+。每条染色体上都显示出显著的特征带,而且带纹的深浅差异明显。强带主要集中在长短臂上。因此,GiemsaC-带方法可以将毛百合(L.dahuricum)的每条染色体区分开。