The morphological variability of the maritae of Phyllodistomum umblae and Phyllodistomum folium (Trematoda: Gorgoderidae) from fish in the Lake Baikal basin

The host variability of adults of Phyllodistomum umblae and P. folium in fishes of the Baikal region has been studied. The absence of considerable geographical variability of P. umblae in Coregonus lavaretus (Lake Baikal, Lake Storsj?n in Sweden) has been shown. The complexes of most stable (the size of acetabulum and eggs, location of acetabulum, ovary and vitelline bodies) and variable (the distance from oral sucker to intestinal bifurcation, distance from intestinal back edge to body end, width of seminal vesicle) features of trematodes of the genus Phyllodistomum have been determined.     

Meiotic drive favors Robertsonian metacentric chromosomes in the common shrew (Sorex araneus, Insectivora, mammalia)

Meiotic drive has attracted much interest because it concerns the robustness of Mendelian segregation and its genetic and evolutionary stability. We studied chromosomal meiotic drive in the common shrew (Sorex araneus, Insectivora, Mammalia), which exhibits one of the most remarkable chromosomal polymorphisms within mammalian species. The open question of the evolutionary success of metacentric chromosomes (Robertsonian fusions) versus acrocentrics in the common shrew prompted us to test whether a segregation distortion in favor of metacentrics is present in female and/or male meiosis. Performing crosses under controlled laboratory conditions with animals from natural populations, we found a clear trend toward a segregation distortion in favor of metacentrics during male meiosis, two chromosome combinations (gm and jl) being significantly preferred over their acrocentric homologs. Apart for one Robertsonian fusion (hi), this trend was absent in female meiosis. We propose a model based on recombination events between twin acrocentrics to explain the difference in transmission ratios of the same metacentric in different sexes and unequal drive of particular metacentrics in the same sex. Pooled data for female and male meiosis revealed a trend toward stronger segregation distortion for larger metacentrics. This is partially in agreement with the frequency of metacentrics occurring in natural populations of a chromosome race showing a high degree of chromosomal polymorphism.     

宽耳犬吻蝠(TADARIDA TENIOTIS INSIGNIS)和普氏蹄蝠(HIPPOSIDEROS PRATTI)染色体组型分析

本文分析了宽耳犬吻蝠(Tadarida teniotis insignis Blyth)和普氏蹄蝠(Hipposideros pratti Thomas)的常规核型,现报道如下。     

Karyometrical analysis of 10 species of the subfamily Monocelidinae (Proseriata,Platyhelminthes) with remarks on the karyological evolution of the Monocelididae

Ten species of the Monocelidinae have been examined. All were found to be regularly diploid. Four of them show the chromosome number n=3 and remarkably similar karyotypes (one pair of large metacentrics, one pair of medium sized metacentrics and one pair of small heterobrachial chromosomes). This set is considered as basic (plesiomorphic) for the family Monocelididae. Three species present n=4 and three species n=5, with an increase of heterobrachial chromosomes. Based on karyometrical data, it is suggested that these complements are derived from the basic complement through fission of one or both metacentric chromosomes, respectively. Further minor chromosome rearrangements, involving centromere position, were observed.     

Preferential segregation of metacentric chromosomes in simple Robertsonian heterozygotes of Sorex araneus

One of the hypotheses explaining preferential transmission of metacentrics among simple Robertsonian (Rb) heterozygotes of the common shrew (Sorex araneus L.) invokes the existence of meiotic drive. Thus far, evidence that metacentrics are favoured at meiosis has been obtained indirectly, on the basis of crosses made under controlled conditions. The aim of the present work was to test the hypothesis in a direct study. We analysed products of chromosome segregation among 12 simple heterozygote male subjects from a wild population, with regard to jl, io, nr and mn Rb fusions. We were able to demonstrate significant segregation distortion in favour of all four metacentrics. The level of preferential segregation was independent either of the composition of chromosome arms or the dimensions of metacentrics. We also found that X chromosomes were favoured over Y1Y2 chromosomes during segregation. We discuss the role of meiotic drive in the evolutionary success of metacentric chromosomes in S. araneus, as well as in the emergence of post-hybridization modifications in the zones of contact between races.     

Robertsonian metacentrics in the mouse

A survey is given on the occurrence, the geographic origin and the arm composition of 27 Robertsonian fusion metacentric chromosomes of wild populations of the mouse. Their study is of twofold interest: a) it is possible to introduce these naturally occurring metacentrics in laboratory strains for experimental use. At present, altogether 34 metacentric chromosomes of different composition are available including 7 cases of metacentrics known from laboratory strains of the mouse. b) With the search for metacentrics in the mouse and with their identification insights are permitted in the role of Robertsonian changes in the course of mammalian evolution — Several separate populations of the mouse with different sets of multiple (up to 9) metacentrics have been found in Switzerland and Italy. Some of the individual metacentrics may occur in different populations. The participation of an acrocentric autosome in the formation of metacentrics seem to be at random, but the sex chromosomes are never included in a metacentric. — Homology of the arms involved in metacentrics is conserved, so that in meiosis of interpopulation hybrids long chains or rings are observed. They may include up to 16 metacentrics arranged according to the alternating homologies of their arms. — Reduction of fertility of single or multiple metacentric heterozygotes and of the interpopulation hybrids is due to mechanisms of segregational imbalance and subsequent prenatal elimination of fetal offspring, but it follows also the pattern of male limited hybrid sterility. — From an evolutionary view point, karyotype rearrangements of Robertsonian type may initiate reproductive isolation, which prepares the ground for further genetic diversification and, as in the case of the mouse, of incipient speciation.     

斯氏并殖吸虫染色体核型分析

最早研究并殖吸虫染色体的是陈品芝(Chea,1937)系采用石蜡切片法,观察到克氏并殖吸虫(P.kellicotti)染色体2n=16,n=8,但未提到其染色体核型。以后近四十年中,未见有关并殖吸虫染色体的报道。而这些年来,国内外并殖吸虫的分类学研究却有了蓬勃的开展,并殖吸虫新种以及对人体致病的虫种不断发现。分类学研究主要以     

Comparison of the karyotypes ofPsathyrostachys juncea andP. huashanica (Poaceae) studied by banding techniques

The karyotypes ofP. juncea (Elymus junceus) andP. huashanica (both outbreeders) were investigated by Feulgen-staining and by C-, N-, and Agbanding, based on a single plant in cach case. Both species have 2n=2x=14 and large chromosomes, possibly a generic character. The karyotype ofP. juncea has 8 metacentrics and 6 SAT-chromosomes with minute, heterochromatic satellites while that ofP. huashanica has 9 metacentrics and 5 SAT-chromosomes only, 2 of which with small, heterochromatic satellites. The C-banding patterns ofP. juncea chromosomes comprise from one to five, mostly small, bands at distal, and terminal positions, while those ofP. huashanica chromosomes are characterized by large telomeric bands in most arms. Banding patterns and chromosome morphology allow identification of the homologues of the seven chromosome pairs inP. juncea, but of two pairs inP. huashanica only. The patterns of both taxa are polymorphic, supporting that both taxa are outbreeders. The karyotypic characters suggest thatP. juncea is more closely related toP. fragilis than either is toP. huashanica. N-banding stains weakly. Silver nitrate staining demonstrates that nucleolus organizers of both species have different nucleolus forming capacities. The presence of micronucleoli suggests that both species have an extra unidentified chromosome with nucleolus forming capacity.     

四种菊头蝠染色体组型分析

本文分析了皮氏菊头蝠(R. pearsoni chinensis),鲁氏菊头蝠(R.rouxi sinicus),角菊头蝠(R.cornutus pumilus)及中菊头蝠(R.affinis)的常规核型,现报道如下。     

Chromosomes of the caryophyllidean tapeworm Glaridacris laruei

The chromosomes of the monozoic tapeworm Glaridacris laruei, from 4 locations in New York State, were studied in leucobasic fuchsin stained squashes of testes and vitelline cells. The diploid chromosome number is 16. Metaphase figures from vitelline cells consist of 3 pairs of metacentrics (“V's”), 4 pairs of acrocentrics (“rods”), and 1 pair of submetacentrics (“J's”). The complement is characterized by a pair of metacentrics 9 μm long, representing 11.5% of the total chromosome length. The shortest are acrocentrics, 2–4 μm long. Meiosis was observed only in spermatogenesis, which proceeds as usual with normal sperm formed after 2 meiotic divisions. Colchicine pretreatment did not facilitate analysis of chromosomes. The scarcity of cell division in 2 populations of G. laruei suggests a possible mitotic rhythm or temperature effect on cell division. Similarities were observed between the the complements of G. laruei and Hunterella nodulosa (2n = 14). A theoretical idiogram, constructed from that of G. laruei, closely resembles H. nodulosa, indicating that there may be a close cytological relationship between these phenotypically different caryophyllids. An idiogram and photographs of chromosomes supplement the paper.     

Karyological studies on Picea ajanensis (Lindl. et Gord.) Fisch. ex Carr. from different regions

Results of karyological study of Picea ajanensis (Lindl. et Gord.) Fisch. ex Carr examined from 13 provenances are presented. In addition to the cytotypes with typical chromosome number (2n = 24), P. ajanensis displays cytotypes with one or two B-chromosomes (2n = 24 + 1 - 2B). Among A-chromosomes, there are 8 pairs of long metacentrics and 4 pairs of shorter meta- or submetacentrics. Among B-chromosomes there are two types of chromosomes: metacentric (B1) and submetacentric (B2) ones. There are many nucleolar chromosomes. Several chromosomes have secondary constrictions. Patterns of B-chromosome distribution within P. ajanensis are have been discussed.     

Variation and Evolution in the Karyotype of Lycoris (Amaryllidaceae) V. Chromosomal Variation in L. sanguinea Maxim.

Abstract In 554 bulbs from 38 populations of Lycoris sanguinea , several chromosomal variations have been discovered. Most of the bulbs have a common karyotype consisting of 22 acrocentric ( A ) chromosomes. Though their frequencies are low, some rearranged chromosomes which are aberrant have been found. The aberrants are as follows: 1. Subtelocentrics ( ST ); 2. Telocentrics ( T' ); 3. Metacentrics ( M' ); 4. Very small acrocentrics (a); 5. Very small metacentrics (m); 6. Acentric fragments ( Ac ); and 7. Dicentrics ( Di ) chromosome. All can be easily suspected to be derived from A s. Some aberrations of the satellite chromosomes have been observed also. In addition, a new karyotype composed of 2n=32=31 A + 1 M' chromosomes has been found.     

Robertsonian chromosomal variation and identification of metacentric chromosomes in feral mice

Cytogenetic studies of feral mice (M. musculus) from various but predominantly Alpine areas of Switzerland, carried out on random samples collected by spot-checks, established the widespread existence of metacentric chromosomes in the somatic karyotype. Despite the finding of the common occurrence of some of the metacentrics in different places, the examination of the possible homology or heterology by breeding procedures revealed the surprising fact that independence, partial or heterobrachial homology of the metacentric chromosomes prevail among mice from different geographical areas. Thus, the general picture is that of an array of different metacentric chromosomes derived from independent events of Robertsonian variation in the process of evolution. — While heterozygosity with independent metacentrics within a Robertsonian system may have a bearing on the fertility rate of a given mouse population, a more severe impairment of the reproductive capacity must be taken into account in mouse populations which possess different metacentrics with mono- or heterobrachial homologies. These conditions favour the assumption of the existence of a selective system of reproductive barriers further subdividing the species in many, more or less stable, micro-populations. — The chromosomal arms (telocentrics) involved in the formation of the metacentric chromosomes could be identified by Q- and G-banding techniques in combination with the results of crossbreeding, and were assigned to the corresponding telocentric autosomes of the mouse (Comm. Standard. Genet. Nomenclat. for Mice, 1972). Most of the telocentric autosomes of the mouse are included in one or more of the metacentrics found in the feral populations. By means of their isolation in separate lines, these metacentrics may be useful in experimental biology as marker chromosomes of defined identity carrying known linkage groups.     

Robertsonian karyotype variation in wild house mice from Rhaeto-Lombardia

The European longtailed house mouse (M. m. brevirostris and domesticus) in the Rhaetian Alps and Lombardia presents a complex system of Robertsonian (Rb) variation and karyotype diversity, several adjoining populations homozygous for multiple Rb metacentric chromosomes, sites of coexistence of different Rb types, and zones of hybridization with non-Rb populations. The original "tobacco mouse" is just one of many local Rb variants, such as those from other Alpine areas (e.g., Orobian Alps) or from Central Lombardia, where a relatively large region within which the population is homogeneous for multi-Rb metacentrics is found. The present study is based strictly on material in which the chromosome arms were identified by G-banding, so that karyotypes within the areas under investigation could be compared. Altogether 111 mice were studied.     

绦虫类细胞遗传学研究 Ⅲ.泡状带绦虫染色体组型分析

本文采用空气干燥法制片,首次报道了泡状带绦虫染色体组型。泡状带绦虫染色体数目为2n=18。染色体组型是由7对中部着丝粒,一对亚中部着丝粒和一对端部着丝粒染色体组成。     

Differentiating sex chromosomes of the dioecious Spinacia oleracea L. (spinach) by FISH of 45S rDNA

Spinacia oleracea L. (spinach) is a dioecious species with both male and female plants having 2n = 2x = 12 chromosomes, consisting of two large metacentrics, two long subtelocentrics, two short subtelocentrics, two acrocentrics, and four submetacentrics. The location of 45S rDNA was investigated on metaphase chromosomes using fluorescence in situ hybridization (FISH). The numbers of 45S rDNA foci in diploid sets of chromosomes from females was six and from males was five. All the fluorescent foci lay in secondary constrictions and the satellites. Our results indicate that an XY-type sex chromosome system could be present in spinach where the Y chromosome lacks a 45S RNA focus.     

Multicolor fluorescence in situ hybridization with combinatorial labeling probes enables a detailed karyotype analysis of Larix principis-rupprechtii

The chromosomes (2n = 2x = 24) of Larix principis-rupprechtii are composed of six pairs of large metacentrics and six pairs of medium-sized submetacentrics. The identification of homologous pairs is hampered by their high degree of similarity at the morphological level in each group. As one of the most extensively used methods in molecular cytogenetics producing chromosome landmarks, fluorescence in situ hybridization (FISH) has significantly facilitated karyotype construction, especially in species with morphologically similar chromosomes. This study developed a simple but effective use of combinatorial labeling probes to distinguish chromosomes of Larix principis-rupprechtii by multicolor FISH. Three highly repetitive sequences in Larix were selected: 25S rDNA hybridized at all of the secondary constrictions of two pairs of metacentrics and the largest pair of submetacentrics; 5S rDNA hybridized at subtelomeric sites of one pair of metacentrics that also harboured 25S rDNA on different arms; LPD family sequences are tandem repeats hybridized at proximal regions of 22 chromosomes. The three different probes were labeled with only two different labels, hybridized to metaphase chromosomes of Larix principis-rupprechtii, simultaneously visualized, and unequivocally distinguished in a single FISH experiment. These multicolor FISH marks largely improved the karyotype analysis of Larix principis-rupprechtii.     

The distribution of Phyllodistomum umblae and Phyllodistomum folium (Trematoda: Gorgoderidae) in the excretory system of fishes

It is shown, that the distribution of Phyllodistomum umblae in the excretory system of all investigated species of salmonids has a principal similarity. The distribution of P. umblae in the excretory system of the Siberian dace and the Siberian roach is distinguished from that of P. folium.     

Dual-color FISH karyotype analyses using rDNAs in three Cucurbitaceae species

Dual-color fluorescence in situ hybridization (FISH) analysis of three Cucurbitaceae species from different genera was conducted using 5S and 45S rDNA probes. In Benincasa hispida (Thunb.) Cogn. (2n=24), the 45S rDNA probe hybridized on two chromosomes, one in the short arm of a medium-sized metacentric chromosome and another at the satellite of a chromosome. The 5S rDNA hybridized at a site proximal to the centromere of the same short arm of the 45S rRNA gene locus that occupied almost the entire short arm. For Citrullus lanatus (Thunb.) Matsum & Nakai (2n=22), the 45S rDNA probe hybridized at sites in the short arms of two chromosomes and the 5S rDNA probe was co-localized with the 45S rRNA locus at the region proximal to the centromere in one chromosome. The 45S rRNA loci occupied almost all of the short arms in both chromosomes. In Cucurbita moschata Duch. (2n=40), the 45S rDNA probe hybridized in five chromosomes in which the 45S rRNA genes occupied almost two-thirds of the chromosomes in two large chromosomes and the entire short arm of a medium-sized chromosome. Two other loci were present in two medium-sized chromosomes, one in the proximal region in the short arm of a chromosome and another at the tip of the long arm of a chromosome. Chromosomes of B. hispida were relatively larger than those of the other two species. The karyotype of B. hispida is composed of two metacentrics and 10 submetacentrics, while that of C. lanatus is composed of seven metacentrics and four submetacentrics and that of C. moschata is composed of 18 metacentrics and two submetacentrics. Comparative chromosome evolution among the three Cucurbitaceae species was attempted using the karyotypes and the chromosomal distribution patterns of the 5S and 45S rDNAs. The results presented herein will be useful in elucidating the phylogenetic relationships among Cucurbitaceae species, and will provide basic data for their breeding programs.     

Contributions to the Cytotaxonomy of the Commelinaceae. Gibasis linearis and its allies

Species of the Gibasis linearis alliance collected in Mexico in 1976 are shown to have a chromosome constitution of x = 6, but x = 5 has also been found in some populations of G. rhodantha and G. speciosa. These two basic numbers are associated with distinctive karyotypes, 2M + 4A and 3M + 2A respectively, which show a Robertsonian relationship with each other. The existence of 2n = 22 in G. speciosa , combining both basic numbers at the amphidiploid level provides evidence of pairing between metacentrics and acrocentrics in such a way as to substantiate the view that fusion or fission of chromosomes is responsible for the modification of basic number. This survey provides a basis for other studies which will determine the chromosome relationships of the species irrespective of chromosome number in this family.