Homoeology of banding sequences and centromeres of Glyptotendipes paripes Edwards, 1929 and G. glaucus meigen, 1818 (Diptera, Chironomidae)

The karyotype analysis of the Glyptotendipes paripes Edwards, 1929 from water reservoirs of Saratov region has been conducted. In the studied population, the following combination of banding sequences predominated: A1.1, B1.1 and G1.1. The frequency of larvae with heterozygous inversions was 72.9 %, the average number of heterozygous inversions per specimen was 0.667, and the most frequent heterozygous inversions were B1.2 (39.5%) and D1.2 (29.2%). Localization of centromeres in the polytene chromosomes G. paripes was defined with the help of C-banding. Homoeology of polytene chromosomes of two chironomidae species (G. paripes and G. glaucus Mg.) has been analyzed and redesignation of chromosomes arms G. paripes has been offered: instead of par D--par A, instead of par C--par B, instead of par A--par D and instead of par B--par C.     

Molecular and cytogenetic analyses provide evidence of the introgression of chromosomal segments from the wild <Emphasis Type="Italic">Cucumis hystrix</Emphasis> into the cultivated cucumber through the bridge of a synthetic allotetraploid

Cucumis × hytivus (2n = 4× = 38) is a synthetic allotetraploid obtained from interspecific hybridization between the cucumber (2n = 2× = 14) and its wild relative C. hystrix (2n = 2× = 24). The synthesis of this species built a bridge for cucumber improvement through gene introgression. Allotriploid and introgression lines (ILs) have previously been produced and characterized with respect to morphology, cytology, and molecular markers. However, no clear evidence of how the chromosomal segments of C. hystrix were introgressed and inherited was found owing to the small size of chromosomes. In the present study, cucumber-C. hystrix introgression lines were developed by backcrossing the allotriploid to North China cucumber breeding line “P01” followed by self-pollination. The introgressed segments of C. hystrix in the ILs were revealed by meiotic pachytene chromosome analysis. Fluorescence in situ hybridization (FISH) was performed on pachytene chromosomes using fosmid clones from cucumber, which confirmed that introgression occurred in the long arm of chromosome 7. Molecular analysis using a set of 53 simple sequence repeats (SSRs) indicated that the chromosomal segments of C. hystrix were introduced into 4 cucumber chromosomes, the short arms of chromosomes 2 and 6, and long arms of chromosomes 3 and 7. The inheritance of alien sequences in the long arm of chromosome 7 was investigated with 21 SSRs in self-pollinated progenies. C. hystrix-specific bands of several SSRs were still present in some individuals, indicating that the introgressed segment was partially preserved. The first unambiguous identification of alien chromosome segments in cucumber ILs using combined molecular cytogenetics could facilitate the determination of effects of wild alleles and promote cucumber improvement.     

NORs inheritance analysis in crossings including individuals from two stocks of rainbow trout (Oncorhynchus mykiss)

Silver nitrate staining of rainbow trouts (Oncorhynchus mykiss) chromosomes, for the identification of the nucleolar organizing regions (NORs), revealed that in individuals from Núcleo Experimental de Salmonicultura de Campos do Jord?o (Brazil) NORs were located in the long arms of submetacentric pair while in specimens from Mount Shasta (USA) NORs were located in the short arms of a submetacentric pair. Cytogenetic analysis of the offspring, obtained through artificial crosses including individuals from both stocks, allowed the identification of NORs in two submetacentric chromosomes, one in the short arms and the other in the long arms, confirming the effectiveness of the hybridization process. Complementary results obtained using the FISH technique with 18S and 5S rDNA probes showed that NOR-bearing chromosomes exhibited a cluster of 5S genes located in tandem with the 18S gene cluster in both stocks. The results allow us to suggest that the difference in NOR-bearing chromosomes found between the two stocks is likely to be due to pericentric inversion involving the chromosome segment where 18S and 5S rDNA genes are located. The presence of ribosomal genes in the long arms of a submetacentric chromosome is apparently a particular characteristic of the rainbow trout stock of Campos do Jord?o and might be used as a chromosome marker in studies of controlled crosses in this species.     

鹿科动物的染色体组型及其进化

染色体是遗传物质的主要携带者。在动植物进化过程中,染色体在数量和结构上的变化,无疑对物种形成起重要的作用。染色体的变化往往引起基因的重新排列和遗传物质的增加或丢失。染色体在结构和数量上的差异还往往造成两个本来很相近的群体间的生殖隔离而形成新种。染色体组型和染色体的带型都代表着种的特性,它为不同动物在分类研究和确定其在进化过程中的位置提供了一个新的和重要的标准。可是,染色体的结构既是稳定的,同时又是可变的。染色体组型的改变是以染色体组的结构特点为基础     

Larval morphology of Agabus clypealis (Thomson, 1867) and A. pseudoclypealis Scholz, 1933 and notes on their distribution (Coleoptera: Dytiscidae)

The third instar larvae of Agabus clypealis (Thomson, 1867) and A. pseudoclypealis Scholz, 1933 are described. Important morphological structures (head, legs, and abdominal segment 8 with urogomphi) are illustrated. Both species share a completely sclerotized abdominal segment 6 with A. setulosus (J. Sahlberg, 1895). Morphological characters and species phenology are discussed in relation to the A. confinis-species group. All available literature records and some new and additional data on distribution of the two species are provided. Agabus clypealis is recorded for the first time from Estonia, and there is no reason to doubt the records of A. pseudoclypealis from Kazakhstan.     

Seasonal variation in diet of Chironomus plumosus (L.) and C. anthracinus Zett. (Diptera: Chironomidae) in mesotrophic Lake Erken

SUMMARY. 1. Microscopic gut content analysis of Chironomus plumosus (L.) and C. anthracinus Zett. collected from 18m depth in mesotrophic Lake Erken. revealed significant seasonal differences between the two species.
2. C. plumosus dietary constituents showed greater seasonal variation than those of C. anthracinus , with diatom contribution to the gut contents reflecting temporal changes in the phytoplankton.
3. Overall the percentage of gut content constituted by detritus, algae, animal remains, and inorganic matter averaged 96%, 4%, 0.4% and 0.03% for C. plurnosus and 97%, 3%, 0.6% and 0.03% for C. anthracinus .
4. Coefficients ot dietary overlap for non-detrital foods decreased markedly from August to September. During this period the proportion of centric diatoms in the guts of C. plumosus increased by 94% while no marked changes were noted in C. anthracinus .
5. C. ptttmosus ingested more diatoms than C. anthracinus , especially during diatom blooms in spring and autumn. These results are consistent with the known differences in feeding behaviour between these two speeies.     

Reduced metaphase I associations between the short arms of homoeologous chromosomes in a <Emphasis Type="Italic">Hordeum vulgare </Emphasis>L. × <Emphasis Type="Italic">H. bulbosum</Emphasis> L. diploid hybrid influences the frequency of recombinant progeny

Hordeum vulgare (cultivated barley) × H. bulbosum (bulbous barley grass) hybrids have been used to obtain disease-resistant recombinant lines (RLs). The RLs contain chromatin transferred from the wild species mostly onto the long arms of recipient barley chromosomes. To determine whether differences in meiotic metaphase I (MI) associations between the long and short arms of homoeologous chromosomes can account for the preponderance of introgressions on the long arms, we carried out fluorescent in situ hybridisation on MI chromosome preparations obtained from pollen mother cells of a diploid interspecific hybrid. By using various probes, we established that MI associations between the long arms occurred more frequently than between the short arms for the five chromosomes tested.     

Chromosomes tell half of the story: the correlation between karyotype rearrangements and genetic diversity in sedges,a group with holocentric chromosomes

Chromosome rearrangements may affect the rate and patterns of gene flow within species, through reduced fitness of structural heterozygotes or by reducing recombination rates in rearranged areas of the genome. While the effects of chromosome rearrangements on gene flow have been studied in a wide range of organisms with monocentric chromosomes, the effects of rearrangements in holocentric chromosomes—chromosomes in which centromeric activity is distributed along the length of the chromosome—have not. We collected chromosome number and molecular genetic data in Carex scoparia, an eastern North American plant species with holocentric chromosomes and highly variable karyotype (2n = 56–70). There are no deep genetic breaks within C. scoparia that would suggest cryptic species differentiation. However, genetic distance between individuals is positively correlated with chromosome number difference and geographic distance. A positive correlation is also found between chromosome number and genetic distance in the western North American C. pachystachya (2n = 74–81). These findings suggest that geographic distance and the number of karyotype rearrangements separating populations affect the rate of gene flow between those populations. This is the first study to quantify the effects of holocentric chromosome rearrangements on the partitioning of intraspecific genetic variance.     

The fauna of the muddy sediments of Lough Neagh, with particular reference to eutrophication

SUMMARY. The main groups of animals found in the muddy sediments of Lough Neagh were Chironomidae (Diptera) and Oligochaeta (mainly Tubificidae). At 8 m depth, the average biomass of the main species in these groups was: Chironomus anthracinus , 2.64gm⁻²; Procladius , 342.8 mgm⁻²; tubificids ( Tubifex, Potamothrix, Aulodrilus, Limnodrilus ), 418.7mgm⁻². At 25m depth C. anthracinus and Procladius were less abundant, C. plumosus was present and among the tubificids Limnodrilus had a higher density (up to 50000m⁻²) often an order of magnitude greater than at 8m. Kinnego Bay, a semi-enclosed, polluted area of the lough, had fewer chironomids than the open lough, with chiefly C. plumosus and Procladius. Limnodrilus was more abundant than at 8m. Dero obtusa (Naididae) was also present, sometimes in large numbers (31000m⁻²).
The response of this fauna to eutrophication in L. Neagh appears to be a diminution in the number of species present, with C. plumosus gradually replacing C. anthracinus as the dominant Chironomus , and tubificids, particularly Limnodrilus , becoming more abundant, A further stage, shown in Kinnego Bay, has Procladius as the most numerous' chironomid. Average total biomass at the three sites was 3.9gm⁻² at 8m, 13.2gm⁻² at 25 m in the main lake, 2.8gm⁻² in Kinnego Bay. At 8m depth, C. anthracinus contributed 76% of the total biomass, at 25m Limnodrilus contributed 74% and C. anthracinus 15%, and in Kinnego Bay, Limnodrilus contributed 40%, C. plumosus 28% and Procladius 20%.     

Molecular cytogenetic study of the European bitterling Rhodeus amarus (Teleostei: Cyprinidae: Acheilognathinae)

The European bitterlings (Rhodeus amarus) from the Eastern locations were cytogenetically examined by conventional and molecular techniques. All analyzed individuals presented invariably the same chromosomal constitution of 2n = 48, with 8 metacentrics + 20 submetacentrics + 20 subtelo-acrocentrics and C-banding positive heterochromatin at the pericentromeric regions in most of the chromosomes. Moreover, some of the chromosomes had short arms entirely built with heterochromatin. GC-rich Ag-NORs (nucleolus organizer regions) were located at the short arms of two submetacentric chromosomes, and the length polymorphism of these regions was found. Multiple location of 28S rDNA sequences with fluorescence in situ hybridization signals was observed on the long and/or short arms of three submetacentric chromosomes including NOR regions and short arms of three to five acrocentric chromosomes in the studied fish. 5S rDNA sites were found on the short arms of two subtelocentric chromosomes, and telomeric repeats were localized at the ends of all chromosomes. Provided results have expanded our knowledge concerning genetic characteristics of the European bitterlings that may be profitable in the conservation programs of this endangered species.     

The karyotype of Nothoscordum arenarium Herter (Gilliesioideae, Alliaceae): A populational and cytomolecular analysis

The genus Nothoscordum Kunth comprises approximately 20 species native to South America. Karyologically, the genus is remarkable for its large chromosomes and Robertsonian translocations. Variation in chromosome number has been recorded in a few polyploid species and it is unknown among diploids. This study presents the chromosome number and morphology of 53 individuals of seven populations of N. arenarium Herter (2n = 10). In addition, karyotype analyses after C-banding, staining with CMA and DAPI, and in situ hybridization with 5S and 45S rDNA probes were performed in six individuals from one population. All individuals exhibited 2n = 10 (6M + 4A), except for one tetraploid (2n = 20, 12M + 8A) and one triploid (2n = 15, 9M + 6A) plant. C-banding revealed the presence of CMA(+) /DAPI (-) heterochromatin in the short arm and in the proximal region of the long arm of all acrocentric chromosomes. The 45S rDNA sites co-localized with the CMA (+) regions of the acrocentrics short arms, while the 5S rDNA probe only hybridized with the subterminal region of a pair of metacentric chromosomes. A change in the pattern of CMA bands and rDNA sites was observed in only one individual bearing a reciprocal translocation involving the long arm of a metacentric and the long arm of an acrocentric chromosome. These data suggest that, despite isolated cases of polyploidy and translocation, the karyotype of N. arenarium is very stable and the karyotypic instability described for other species may be associated with their polyploid condition.     

Quinacrine fluorescence of variant and abnormal human Y chromosomes

Quinacrine fluorescence has been used to examine variant and abnormal human Y chromosomes, at interphase and mitosis. The length difference in variant Y chromosomes has been shown to involve the highly fluorescent segment only. Eight abnormalities of the Y chromosome have been positively identified, two isochromosomes of the long arms of the Y, five pericentric inversions, and a dicentric Y chromosome with two long arms. Contributory evidence for two further abnormalities, a ring Y and a dicentric with two short arms, is also given.     

Chromosomal location of genes controlling seed proteins in species related to wheat

Summary The seed proteins of Chinese Spring wheat stocks which possess single chromosomes from other plant species related to wheat have been separated by gel electrophoresis in the presence of sodium dodecyl sulphate. Marker protein bands have been detected for both arms of barley chromosome 5, chromosome E (= 1R) and B (= 2R) of rye, chromosomes A,B (= 1C^u) and C (= 5C^u) of Aegilops umbellulata and chromosomes I and III of Agropyron elongatum. These studies, and previous findings, indicate that chromosome 5 of barley, chromosome 1R of rye, chromosome I of Ag. elongatum and possibly chromosome 1C^u of Ae. umbellulata are similar to chromosomes 1A, 1B and 1D in hexaploid wheat in that they carry genes controlling prolamins on their short arms and genes controlling high-molecular-weight (apparent molecular weight greater than 86,000) seed protein species on their long arms. These findings support the idea that all these chromosomes are derived from a common ancestral chromosome and that they have maintained their integrity since their derivation from that ancestral chromosome.     

Early replication banding in <Emphasis Type="Italic">Leporinus</Emphasis> species (Osteichthyes,Characiformes) bearing differentiated sex chromosomes (ZW)

There are few examples of differentiated sex chromosomes in fishes. In the genus Leporinus, seven species present a highly differentiated ZW system, derived from heterochromatinization process. Cytogenetic analyses carried out in three of these fish species, Leporinus obtusidens, L. elongatus and L. reinhardti, through RBG-banding, showed late replication bands, coincident with heterochromatic regions in both Z and W chromosomes. A similar interstitial early replication segment was observed in the complex heterochromatic region along the Wq arms in the three species, which might correspond to a pseudoautosomal segment (SD, sex determining locus). Asynchrony related to the replication pattern among different Z chromosomes was not observed. When the identification of nuclear organizer regions by silver nitrate was performed over chromosomal preparations previously exposed to 5-bromo-2′-deoxyuridine (BrdU), remarkable positive signals at interstitial and telomeric position were observed on the q arms of W chromosomes in the species L. elongatus and L. reinhardti. The absence of 18S ribosomal RNA gene loci in this region, formerly demonstrated by FISH, indicates that this argentophilic behavior is putatively due to heterochromatin decondensation caused by BrdU incorporation, favoring such Ag+ reaction. Early and late replication bands were also observed in the heterochromatic portions of Z and W chromosomes, indicating that euchromatic and heterochromatic regions are interspersed. The present data suggest a significant level of heterochromatic complexity in the sex chromosomes of each species. On the other hand, the replication pattern shared by them supports a monophyletic origin.     

Sequential meiotic prophase development in the pubertal Indian pygmy field mouse: synaptic progression of the XY chromosomes, autosomal heterochromatin, and pericentric inversions.

Sequential meiotic prophase development has been followed in the pubertal male pygmy mouse Mus terricolor, with the objective to identify early meiotic prophase stages. The pygmy mouse differs from the common mouse by having large heterochromatic blocks in the X and Y chromosomes. These mice also show various chromosomal mutations; for example, fixed variations of autosomal short arms heterochromatin among different chromosomal species and pericentric inversion polymorphism. Identification of prophase stages was crucial to analyzing effects of heterozygosity for these chromosomal changes on the process of homologous synapsis. Here we describe identification of the prophase stages in M. terricolor, especially the pachytene substages, on the basis of morphology of the XY bivalent. Based on this substaging, we show delayed pairing of the heterochromatic short arms, which may be the reason for their lack of chiasmata. The identification of precise pachytene substages also reveals an early occurrence of "synaptic adjustment" in the pericentric inversion heterobivalents, a mechanism that would prevent chiasma formation in the inverted segment and thereby would abate adverse effects of such heterozygosity. The identification of pachytene substages would serve as the basis to analyze the nature of synaptic anomalies met in M. terricolor hybrids (which will be the basis of a subsequent paper).     

Chromosome evolution in fish: sex chromosome variability in Eigenmannia virescens (Gymnotiformes: Sternopygidae)

New data are presented on the sex chromosomes of the fish species Eigenmannia virescens (Gymnotiformes, Sternopygidae). A new finding, involving the occurrence of ZZ/ZW sex chromosomes, is described in specimens sampled from the S?o Francisco and Amazon river basins in Brazil. All individuals had a chromosome number of 2n = 38. The homologs of the sex chromosome pair from the S?o Francisco river basin sample differed only in their morphology, while those from the Amazonian sample differed both in morphology and heterochromatin pattern. A possible model for the evolution of the sex chromosomes in E. virescens is proposed, including data from populations from the Paraná (Brazil) river basin, in which male heterogamety has already been described. The occurrence of different sex chromosome systems in species and populations of the neotropical freshwater fish fauna is discussed.     

Studies on the chromosomes of genusNycticebus

The karyotypes of three species (N. coucang, N. intermedius, andN. pygmaeus) of genusNycticebus, collected from the southern Yunnan of China, have been studied. All individuals from three species possess 2n=50 chromosomes, and all chromosomes in their complement are biarm chromosomes. The karyotype of slow loris (N. coucang) is characterized by having a secondary constriction and Ag-NORs in the short arms of pair No. 1. The G-banding patterns of three species are very similar. Three species are found to have multiple Ag-NORs. InN. coucang, NORs were observed on five pairs (Nos. 1, 6, 9, 15, and 23) and inN. intermedius andN. pygmaeus, NORs were found on four pairs (Nos. 6, 9, 15, and 20). This finding indicates that slow lorises, as primitive primates, also have multiple NOR-bearing chromosomes. Finally, the classification of genusNycticebus by karyotype analysis is discussed, and our results suggest that there are at least two valid species, namely:N. coucang andN. pygmaeus.     

Intercalar satellites of human acrocentric chromosomes as a cytological manifestation of polymorphism in GC-rich material?

Summary Fifteen unrelated individuals were found among the patients of the Cytogenetics Laboratory who possessed multiple-satellited marker chrmosomes (14 with double satellites and 1 with triple satellites). Cytogenetic analysis was carried out by means of a conventional staining method and also by R, C, and Q banding and by the technique of silver staining. The intercalar structures of all 15 cases differed from the terminal satellites in their biochemical composition: they were resistant to heat denaturation, and stained heavily with the R-banding technique. Accordingly, they consisted of GC-rich material identical with that which in varying quantity is a regular constituent of the short arms of acrocentric chromosomes. The findings described indicate that any larger accumulation of such R band-positive material tends to dissociate from the basal segment of short arms by a proximal secondary constriction. We therefore assume that the formation of intercalar satellites may be interpreted as a cytological consequence of extreme natural R polymorphism.     

Comparison of the Giemsa C-banded karyotypes of Hystrix coreana and H. patula (Poaceae, Triticeae)

The karyotypes of Hystrix coreana from eastern USSR and H. patula from USA were investigated by Giemsa C-banding. Both species are outbreeders and have 2n = 4x = 28. The karyotype of two plants of H. coreana has 10 metacentric, 6 submetacentric, 8 heterobrachial and 4 SAT chromosomes; two plants differed by having 12 metacentric, 4 submetacentric, 8 heterobrachial and 4 SAT-chromosomes, and 10 metacentric, 4 submetacentric, 9 heterobrachial and 5 SAT-chromosomes, respectively. The C-banding pattern had no or few inconspicuous intercalary bands, but conspicuous telomeric C-bands in one or both arms giving a high content of heterochromatin (16.3–18.2%). The chromosome complement of one plant of H. patula had 8 metacentric, 6 submetacentric, 8 heterobrachial and 6 SAT-chromosomes. The C-banding pattern had between 1 and 4 intercalary or centromeric bands and conspicuous telomeric bands on one or both arms giving a high content of constitutive heterochromatin (16.4%).