Analysis of chromatin-associated fiber arrays

The distribution of constitutive heterochromatin has been investigated in four chromosomal races of the grasshopper Caledia captiva (2n= 23 /24 ) by the C-banding technique. Each of the four races was found to have a distinctive banding pattern which is associated with the inter-racial differences in chromosomal rearrangements. — The Ancestral race has a telocentric chromosome complement with large procentric C-bands which are structurally double on six pairs of chromosomes. The centromeres are unstained. — The General Purpose race has a C-banding pattern very similar to that seen in other Acridine grasshoppers with the majority of its chromosomes showing a centromeric localisation of the bands. — The two southern races, which show a complex polymorphism for presumed pericentric inversions on all twelve chromosomes, also show an unusually high level of interstitial and terminal C-bands. The different locations and numbers of these bands allow unambiguous identification of all the chromosome pairs within the complement. — In two cases, there is good evidence to indicate that a C-band redistribution between acrocentric and metacentric chromosomes has occurred by pericentric inversion. Furthermore, C-band variation on the long arm of the metacentric X-chromosome indicates the presence of a large paracentric inversion. This double inversion system has involved over 95% of the X-chromosome. — The interstitial and terminal C-bands probably have not resulted from heterochromatin movement within the complement but, more likely, have arisen by saltatory duplication of pre-existing sequences on the chromosome. — A new nomenclature system for banded chromosomes is proposed which allows most kinds of chromosomal restructuring and rearrangement to be adequately enumerated.     

Population cytogenetics of the genus Caledia (Orthoptera: Acridinae)

The genus Caledia contains two species. C. species nova 1 is restricted to the Oriomo Plateau of S.W. Papua and has a complement of twelve telocentric chromosomes. The second species C. captiva has a much wider distribution pattern—from S.W. Papua in the North, down the entire Eastern seaboard of Australia to Southern Victoria. It is also found in the Northern Territory. Although the chromosome number is the same as C. species nova 1, four major and distinct chromosomal races can be distinguished in C. captiva. — The basic ancestral race is found in Tropical North Queensland at the base of the Cape York Peninsula. All twelve chromosomes are telocentric and the karyotypic organization is similar to that found in C. species nova 1 and in other Acridines. A second, general purpose karyotypic race has a wide distribution between S.W. Papua, Arnhem Land and the East Australian coast as far South as Brisbane. It is considered a derivative form of the ancestral type and is fixed for small pericentric inversions on seven pairs of chromosomes. In the South-Eastern Queensland region there exists a further race which carries large pericentric inversions on all the autosomes and the X chromosome. The situation here is confounded since the basic chromosomes can be represented as either acro or telocentrics. Various levels of polymorphism for the inversions exist between different chromosomes in different populations indicating considerable differentiation within this zone. This race is almost completely surrounded by the general purpose karyotype where the races are contiguous in certain parts of the range. — The South-Eastern corner of Australia is characterised by a chromosome race quite different from those found further North. Here a complex pericentric inversion system exists involving a series of seven small inversions and larger inversions on chromosomes 1, 2, 4 and 10. Chromosomes 2 and 4, in particular, are highly polymorphic. — The presence and persistence of these 4 chromosomal races can be accounted for in terms of the known climatic changes which have occurred in this region in the recent past.     

Chromosome and C-heterochromatin polymorphisms in the Italian newt,Triturus italicus

A combined chromosome and C-heterochromatin polymorphism in pair 12 in the complement of the newt species, T. italicus is described. The C-heterochromatin polymorphism is presumably due to a loss in the proximal C-band, whereas the chromosomal polymorphism has its origin in two different independent pericentric inversions both including the centromere and the proximal C-band of chromosome 12. The double-inversion polymorphism has a wide distribution over the range and follows a clear bipolarity between a northern area where the karyotype is homomorphic for the standard type of pair 12 (ST/ST) and an opposite area where the ST type is completely replaced by variant M₁ and M₂ metacentric chromosomes 12. Various karyophylogenies are possible, but the simplest and the most probable presumes an ancestral karyotype of ST/ST and a mechanism of gradual replacement of the heterobrachial chromosome ST by two independent pericentric inversions. The present data are discussed in relation to existing theories on karyological evolution of Urodeles and the functional significance of telocentric chromosomes suggested by Sessions et al. (1982).     

Chromosome banding in Amphibia

The chromosomes of the South American marsupial frogs Gastrotheca fissipes, G. ovifera, G. walkeri and Flectonotus pygmaeus were analyzed by means of conventional and various banding techniques. The karyotypes of G. ovifera and G. walkeri are characterized by highly differentiated XY/XX sex chromosomes. Whereas the X chromosomes and autosomes contain large amounts of constitutive heterochromatin, extremely little heterochromatin is located in the Y chromosomes. This is in contrast to all previously known amphibian Y chromosomes and the Y chromosomes of most other vertebrates. In the male meiosis of G. walkeri, the euchromatic segments of the heteromorphic XY chromosomes show the same pairing configuration as the autosomal bivalents. The karyotype of F. pygmaeus is remarkable for the unique presence of telocentric chromosomes and the high frequency of interstitially located chiasmata in the meiotic bivalents. The evolution of the karyotypes and sex chromosomes, the structure of the various classes of heterochromatin and the data obtained from meiotic analyses of the marsupial hylids are discussed.     

C-heterochromatin variation in the genus Eumigus (Orthoptera: Pamphagoidea)

Eumigus punctatus, E. monticulus and E. cucullatus all have 2n=19 and similar chromosome morphology, all the elements being telocentric. In E. cucullatus there are C-bands in all chromosomes, but not in E. monticulus. The possible origins of these differences and their cytotaxonomic significance are discussed.     

Chromosome polymorphism in the Italian newt,Triturus italicus

A chromosomal variation, changing shape and C-banding pattern of chromosome XII of Triturus italicus was detected among the offspring of two F₁ hybrid families of T. italicus × T. vulgaris meridionalis . In both families a number of individuals appeared to have a metacentric instead of the expected subtelocentric chromosome XII of T. italicus. — Investigations in three well separated localities in the range of the species showed the polymorphism to have a wide distribution and to be part of a complex pattern involving at least two inversions and (presumably) deficiencies of large C-bands. At meiosis, the shape of bivalent XII, and the location and frequency of chiasmata in the bivalent varied with the karyomorph involved. It is suggested that large rearrangements may still play an important role in the karyological evolution of Triturus.     

Variable karyotype with B-chromosomes in Bellevalia saviczii (Liliaceae)

Bellevalia saviczii (Liliaceae), a hexaploid (2n = 6x = 24), was collected from mountain slopes in the Shiraz valley, southern Iran. The basic karyotype consists of one long metacentric chromosome, a slightly shorter acrocentric, and two shorter submetacentrics. In 32% of the plants, one and sometimes two of the acrocentrics (IIa) appeared with a pericentric inversion that changed it into a metacentric (IIm). This metacentric IIm was present in a Hardy--Weinberg ratio throughout the collection range of more than 300 km. A number of aneuploids were found, pentasomics [2n – 1 = 23 (4.9%)], heptasomics [2n + 1 = 25 (2.5%)], and one octasomic [2n + 2 = 26 (0.3%)]. Re-assorted karyotypes with 2n = 24, but with odd numbers of two of the chromosomes, were also present (6.6%). B-chromosomes were found in root meristems and in pedicels in a number (19.1%) of the plants that grew around a 30 km marsh. Their numbers ranged from 1B to 8Bs per plant peaking in the 2B mode. The B-chromosomes (two polymorphs with terminal and near-terminal sticking points) were telocentric with a few metacentric iso-Bs. No B-carrying plants were found in the drier regions away from the marsh. The B-frequency distribution for aneuploids and pericentric inversions was much different than for the standard euploid. Dr Mark Gettner died on November 2nd, 2002. He is fondly remembered by his family, his many students and friends for his kindness and generosity, and for his dedication to his scientific work. Dr Broun is the son-in-law of Dr Gettner and he will be the corresponding author for this article (pb22@york.ac.uk).     

Chromosomal evolution within the family Estrildidae (Aves) II. The Lonchurae

Thirteen species of estrildid finches belonging to the Lonchurae were examined cytogenetically by G- and C-banding. The major forms of karyotypic change, both within and between species, were pericentric inversions and changes in the amount of heterochromatin. It appears that the direction of chromosome change in this lineage is towards an entirely telocentric karyotype because inversions converting a biarmed chromosome into a telocentric one only occur when all the macrochromosomes of smaller size are also telocentric. A comparison of hybrid fertility data and karyotypic differences indicates that genic factors affecting gonadal development, and not chromosomal rearrangements, are the primary influence in determining hybrid fertility. The chromosomal data was also used to clarify systematic relationships within the Lonchurae and demonstrate that the genus Lonchura as presently construed is polyphyletic.     

The karyotype of some Australian species of Macropathinae (Gryllacridoidea — Rhaphidophoridae)

The chromosome number of eight species of Australian Macropathinae are reported in this paper. They show basically the same karyotype as four South-American species of the genus Heteromallus. The basic karyotype for the subfamily Macropathinae is established as 2n=45-and 46, with an XO-XX sex mechanism; the X is metacentric.The genus Cavernotettix comprises a cytologically modern and dynamic group of species in which the basic karyotype is modified in several directions. There are two species with XY-XX sex mechanisms and three with X₁X₂YX₁X₁X₂X₂ systems. The latter mechanisms are reported for the first time in Gryllacridoidea.Sponsored by C.A.P.E.S. (Río de Janeiro, Brasil) and F.A.P.E.S.P. (São Paulo, Brasil).     

The founder effect theory: quantitative variation and mdg-1 mobile element polymorphism in experimental populations of Drosophila melanogaster

The chromosomes of 14 specimens of the genus Reithrodon from three different localities of Argentina and two localities of Uruguay were studied using G-and C-banding techniques. Specimens of Uruguay showed a karyotype of 2n=28 chromosomes having a large metacentric X, and a telocentric Y chromosome. This karyotype is very similar to that recently described in a sample from southern Brazil, differing only in the nature of the Y chromosome, which is metacentric in the Brazilian form. All specimens from Argentina showed a 2n=34 karyotype, differing from the Brazilian karyotype by two centric fusions, an acquisition of chromosome material, and at least one pericentric inversion, and by the telocentric nature of both the X and the Y chromosomes. G-and C-banding suggest that the metacentric gonosomes in the Brazilian form resulted from a double autosomal-X-Y Robertsonian translocation. The Uruguayan cytotype is interpreted as derived from a hypothetical neo-X/Y₁Y₂ ancestral form by the secondary loss of the Y₁ chromosome. The karyotypic differences between the Brazilian-Uruguayan and the Argentinian forms afford evidence of species differentiation. It is proposed to assign the former to Reithrodon typicus, and the later to R. auritus.     

Reaktionen von Zilpzalp und Fitis (Phylloscopus collybita, Ph. trochilus) auf verschiedene Gesangsformen des Zilpzalps

Zusammenfassung 1. Die mitteleuropäische, die spanische und die kanarische Gesangsform des Zilpzalps sind voneinander klar verschieden.2. Die Zilpzalp- von Teneriffa (kanarische Inseln) und aus Mitteleuropa reagieren auf ihre vom Tonband vorgespielten Gesänge wechselseitig wie verschiedener Arten, d. h., nur einzelne werden angelockt.3. Zilpzalp- aus Mitteleuropa verhalten sich gegenüber der spanischen Gesangsform des Zilpzalps wie gegenüber artfremdem Gesang. Spanische Zilpzalp- werden von Gesangsformen des Zilpzalps aus Mitteleuropa und den kanarischen Inseln zu einem hohen Prozentsatz angelockt (86,6 und 66,6%).4. Die Zilpzalp-Populationen in Mitteleuropa, Spanien und auf den kanarischen Inseln befinden sich vermutlich auf verschieden weit fortgeschrittenen Stufen der Artaufspaltung.5. Interspezifische Kontrastbetonung ist wahrscheinlich nicht die Ursache für die großen Unterschiede zwischen dem Gesang des Fitis und des mitteleuropäischen Zilpzalps.

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Reactions of the Chiffchaff and Willow-Warbler to different song forms of the Chiffchaff

Summary 1. The song forms of the Chiffchaff in Central Europe, in Spain and on the Canary Islands are clearly distinct from each other.2. Chiffchaff males of Tenerife (Canary Islands) and Central Europe react to the playback of each other songs in the same way, as to songs of other species, i. e. only a few males being attracted.3. Chiffchaff males of Central Europe behave in the same way to the Spanish song form of the Chiffchaff as to songs of another species. A high % of Spanish Chiffchaff males are attracted to song forms of the Chiffchaff of Central Europe (86,6) and of the Canary Islands (66,6).4. Chiffchaff populations in Central Europe, Spain and on the Canary Islands should stay split as they are different evolutionary stages.5. Interspecific contrast reinforcement is probably not the cause of the differences between the song of the Willow Warbler and the song of the Chiffchaff of Central Europe.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Patterned disjunction in Drosophila melanogaster. I. Assortment of SPA pol /+ and X,Y in the stock N1

N1 (= Nijmegen 1) D. melanogaster heterozygous for sparkling poliert (4) (= pol, here) were backcrossed as single pairs. When were not selected for departure from 1/1, pol/pol ⁺, many exceptional ratios were observed even though the net for all 67 pairs was approximately one-to-one; in the same experiment a net excess of was observed. In a second experiment were selected for departure from 1/1, pol/pol ⁺ratios. The net pol/pol ⁺ratios became significantly different from the 1/1 expected but the sex ratio approached normal. Lineage of the males in the second experiment were recorded and displayed as pedigrees. These together with tabulated data suggest that in some pairs, one of the four categories pol , pol , pol ⁺, pol ⁺ may be significantly greater or less than 1/4 of the total offspring recovered.     

Complex sex-linked fusion heterozygosity in the Australian huntsman spider Delena cancerides (Araneae: Sparassidae)

In the vast majority of spider species studied to date, the karyotype is homogeneous in morphology and exclusively telocentric. The sex-determining system consists of one to three X chromosomes in the male and, correspondingly, two to six in the female. This is the case in species of huntsman spiders belonging to the genera Heteropoda (2n=40+3X), Isopoda, Olios, and Pediana (2n=40+3X) and some populations of the colonial species Delena cancerides (2n=40+3X). In other populations of D. cancerides, wholesale fusion of the karyotype has occurred, reducing the standard huntsman karyotype of 43 telocentric chromosomes to 21 metacentrics and 1 telocentric. Eight of the centric fusion products, including an X-autosome fusion, are maintained in the heterozygous condition in males and, with the single telocentric, form a chain of nine chromosomes at meiosis. The two complexes comprising the chain behave as neo-X and neo-Y chromosomes, and thus the ancestral X₁X₂X₃X₁X₁X₂X₂X₃X₃ sex-determining system has been converted to a system of six X and four Y chromosomes in the male and twelve X chromosomes in the female. Since sex-linked complex heterozygosity is also found in a number of species of social termites, it is suggested that such heterozygosity may have adaptive significance for a colonial lifestyle. Breakdown products of the chain of nine are present in specimens of D. cancerides from Canberra and these appear to represent hybrid products between the 2n=22 and 2n=43 forms. Hybridisation may also have been involved in the origin of the chain-forming races.     

Chromosome multiformity in the genus Ctenomys (Rodentia,Octodontidae)

The karotypes of eleven species of the South American burrowing rodents, genus Ctenomys are described, and information on the somatic number of two other species of the same genus is given. The studied species are: C. torquatus (2n =68), C. tuconax (2n =61), C. minutus (2n=50), C. talarum (2n= 48), C. porteousi (2n=48), C. cf. minutus (2n=48), C. australis (2n=46), C. azarae (2n=48), C. latro (2n=42), C. magellanicus fueguinus (2n=36), C. tucumanus (2n=28), C. opimus luteolus (2n=26), and C. occultus (2n =22). This extreme intrageneric variation in somatic number is also reflected by a great amount of diversity in chromosome structure. Karyotypes seem to be rather constant at the species level. Autosomal polymorphism has been found in two of the species, namely C. talarum and C. latro. The hypothesis of the superimposition of Robertsoman rearrangements, pericentric inversions and translocations in the evolution of the karyotype of Ctenomys is advanced. The direction of chromosome change, either toward increase or decrease in chromosome number, is discussed. It is emphasized that high chromosome multiformity is correlated in Ctenomys with a rapid and explosive pattern of species diversification; the meaning of the small size of populations in enhancing the role of chromosome rearrangements in the evolution of Ctenomys is discussed.     

INFLUENCE DU SUPERPARASITISME SUR LA DURÉE DU DÉVELOPPEMENT LARVAIRE ET LE POIDS DU PARASITOÏDE LIXOPHAGA DIATRAEAEÉLEVÉ DANS UN HÔTE DE SUBSTITUTION GALLERIA MELLONELLA

Résumé G. mellonella infestée au dernier stade larvaire avec 1, 2, 3 ou 5 planidia/hôte (ph/H) produit 1 à 5 pupes/hôte (pu/H). La mortalité des chenilles augmente avec le nombre de pl/H. Le poids des pupes et décroît avec un nombre croissant de pu/H (18,2 à 12,9 mg pour les et 12,5 à 9,7 mg pour les ). Le développement larvaire dure 8,7 j. chez les et 8,3 chez les ; il est peu affecté par le superparasitisme. Avec 1, 2, 3 et 5 pl/H nous obtenons 0,84–1,61–2,17 et 3,43 pu/H et 0,81–1,48–2,10 et 3,11 imagos/H. L'optimum est de 3 pl/H ou 1 à 2=pl/H pour obtenir des parasitoïdes plus lourds.

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Summary The influence of superparasitism on larval and pupal development is investigated. Last-larval instar G. mellonella (200±5 mg) were infected with 1, 2, 3 or 5 planidia/host (pl/H) producing 1 to 5 pupae per host (pu/H). Host mortality (8.6–8.3–14.3 and 22.2%) increased with the number of planidia. The planidia may transmit a bacteriosis. Pupal weight ( and ) decreased as number of pu/H increased. pupae were heavier than ones: 12.9 to 18.2 mg for against 9.7 to 12.5 mg for . Larval development lasted slightly longer for (8.7 d.) than for (8.3 d.), and its duration was little affected by superparasitism. 1, 2, 3 or 5 pl/H yielded 0.84–1.61–2.17 and 3.43 pu/H and 0.81–1.48–2.10 and 3.11 adults/H. An optimum was obtained with 3 planidia of L. diatraeae on G. mellonella or 1 to 2 to obtain heavier parasitoids.

     

Chromosome Inversion Polymorphisms Influence Morphological Traits in <Emphasis Type="Italic">Trimerotropis Pallidipennis</Emphasis> (Orthoptera)

Trimerotropis pallidipennis is a New World grasshopper whose South-American populations are polymorphic for six pericentric inversions. Previous work has demonstrated that the frequences of these inversions correlate with climatic variables, and hence a possible adaptive pattern was put forward. In the present work we analysed a sample of a natural population of T. pallidipennis to ascertain whether the chromosomal inversions have effects on exophenotypes. Two hundred and sixty-eight males coming from a natural population at Uspallata, Mendoza Province, Argentina were analysed, and it was observed that most inversions had significant effects on phenotypes. Furthermore, some body size-related characteristics (such as tegmina length) were correlated with the number of inversions. Individuals from populations at higher altitude or latitude (i.e., at lower minimum temperatures), along with higher frequencies of standard sequences, were significantly smaller, and this coherence between interpopulational with intrapopulational results may indicate that the diminished body size of the standard sequence-carrying individuals may be caused by an effect of the inversions, or genes within the inversions, on body size. We finally put forward the hypothesis that reduced body size in a context of reduced minimum temperature may be a response to shortened development season, and so smaller individuals may be advantageous.     

Complex sex-determining mechanisms in three species of South American grasshoppers (Orthoptera,Acridoidea)

The karyotype of three species of South American grasshoppers are studied in this paper. Leiotettix sanguineus has two chromosome races, one of them with 2n=23 and an XO sex mechanism and the other, as far as we know limited to the Cerro Chato population, with 2n=22 and an XY sex mechanism. Leiotettix politus has two kinds of individuals, one with 2n=14 and XY sex chromosomes and the other 2n=13 and an X₁X₂Y mechanism. Dichroplus dubius presents 2n=21 and an X₁X₂Y sex chromosomes. One of the three specimens studied shows aberrant behaviour in the meiotic process.     

Non-reciprocal gonadal dysgenesis in hybrids of the chironomid midge Chironomus thummi II. Gonadal-dysgenesis inducing chromosomes

Females of Chironomus thummi thummi (stock H1) were backcrossed with hybrid males of the cross Ch. thummi thummi (H1) x Ch. thummi piger (E) in order to test which of the four piger chromosomes determine the temperature sensitive non-reciprocal gonadal dysgenesis originally observed in the thummi x piger hybrids. In the backcross rudimentary gonads as well as normal gonads were found irrespective of the chromosome constitution of the individuals. The highest frequency of abnormal gonads (63%) occurred in backcross larvae which received piger chromosomes I and III. Statistical evaluation of the data showed that piger chromosome I is able to induce 44% dysgenic gonads. The gonadal-dysgenesis inducing ability of piger chromosome III is only recognizable if also piger chromosome I is present in the genome. The piger chromosomes II and IV do not have a statistically significant influence on the frequency of abnormal gonads.Arguments are presented for the assumption that the factors determining rudimentary development of the gonads are located distally to those pericentric chromosome regions of the piger chromosomes I and III that in polytene chromosomes show differences in the size of bands in comparison with the homologous thummi regions. The question is discussed whether the rudimentary development of the gonads is caused by gene pairs with an epistatic form of interaction or by the activity of transposable elements.     

The genomic sequence for Prader-Willi/Angelman syndromes' loci of human is apparently conserved in the great apes

Chromosomal changes through pericentric inversions play an important role in the origin of species. Certain pericentric inversions are too minute to be detected cytogenetically, thus hindering the complete reconstruction of hominoid phylogeny. The advent of the fluorescence in situ hybridization (FISH) technique has facilitated the identification of many chromosomal segments, even at the single gene level. Therefore the cosmid probe for Prader-Willi (PWS)/Angelman syndrome to the loci on human chromosome 15 [ql 1-12] is being used as a marker to highlight the complementary sequence in higher primates. We hybridized metaphase chromosomes of chimpanzee (PTR), gorilla (GGO), and orangutan (PPY) with this probe (Oncor) to characterize the chromosomal segments because the nature of these pericentric inversions remains relatively unknown. Our observations suggest that a pericentric inversion has occurred in chimpanzee chromosome (PTR 16) which corresponds to human chromosome 15 at PTR 16 band pl 112, while in gorilla (GGO 15) and orangutan (PPY 16) the bands q11-12 complemented to human chromosome 15 band q11-12. This approach has proven to be a better avenue to characterize the pericentric inversions which have apparently occurred during human evolution. Genetic divergence in the speciation process which occurs through chromosomal rearrangement needs to be reevaluated and further explored using newer techniques.Correspondence to: R.S. Verma     

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.