Chromosomal polymorphism of Rattus rattus (Linnaeus, 1758) (rodentia: muridae) in Central Anatolia

In this study, conventionally stained, C- and Ag-NOR banded karyotypes of Rattus rattus from Central Anatolia are presented. The karyotype of the specimens from Ankara and (Cankiri provinces consist of 2n = 38, NF = 60 and NFa = 58 while the karyotype of Kirikkale specimens consist of 2n = 38 and NFa = 59 due to a heteromorphic autosome pair. The X is a large to medium sized acrocentric and the Y chromosome is a small acrocentric in all examined specimens. Constitutive heterochromatin is located in the centromeric regions of all pairs of autosomes and the X chromosome. Nucleolar organizer regions (NORs) are located only in 3 autosome pairs.     

Cytogenetic study on Microtus guentheri (Danford and Alston, 1880) (mammalia: rodentia) from Turkey: constitutive heterochromatin distribution and nucleolar organizer regions

Conventionally stained, C- and Ag-NOR banded karyotypes of Guenther's vole, Microtus guentheri were studied from Turkey. The species possesses a karyotype of 2n = 54, NFa = 52 and NF = 54 in specimens from Kahramanmara? and Gaziantep provinces, whereas NF = 56 in females and NF = 55 in males were found in individuals from Kirikkale and Nev?ehir provinces. The X chromosome was a large acrocentric (NF = 54) or submetacentric (NF = 55, 56) while the Y chromosome was a small telocentric in all specimens examined. Blocks of constitutive heterochromatin were located in the pericentromeric areas of autosomes including the X chromosome. Nucleolar organizer regions (NORs) were located at the telomeric regions of the short arms of five acrocentric pairs and centromeric regions of two telocentric pairs in the Nev?ehir and Kirikkale specimens.     

Chromosome analysis of 82 species of Scarabaeoidea (Coleoptera), with special focus on NOR localization

The aim of this study was the identification of the ancestral location of the nucleolus organizer region (NOR) in the Scarabaeoidea superfamily, and its evolutive trends in the karyotypes. For this purpose, the mitotic and meiotic chromosomes at pachynema of 82 species belonging to 4 families and 8 subfamilies, including 49 species without any published data, were examined after Giemsa staining, C-banding and NOR staining. It could be perceived that most karyotypes are composed of 18 nonacrocentric autosomes, an acrocentric X and a punctiform Y. NORs are frequently located on the X independent of its morphology. In contrast, autosomal NORs are frequently on the rare acrocentric short arms. Thus, it could be shown that the ancestral karyotype was very probably composed of 18 metacentric/submetacentric autosomes, an NOR carrier acrocentric X and a punctiform Y. The NOR translocation on autosomes parallels the passage to their acrocentric morphology. It is proposed that the frequent location of the NOR on the X of beetles, and possibly other insects, is made possible by their mode of dosage compensation of the X chromosome, consisting in the overexpression of the unique X of the males.     

Genetic studies in representatives of genusRhipidomys (Rodentia, Sigmodontinae) from Brazil

Karyotypic polymorphism of five taxa of the rodent genusRhipidomys from the Brazilian Amazon and Cerrado biomes was analysed.Rhipidomys nitela Thomas, 1901 from Amazon has 2n=48, FN=68. The other species, all have 2n=44, but can be separated into two groups, one with high FNs (76, 80) and the other with low FNs (48, 52). Two cytotypes ofR. mastacalis (Lund, 1840) with high FNs were trapped in four localities of the Cerrado, showing 19 and 17 biarmed autosomes, respectively. A low FN (48) was observed inR. leucodactylus (Tschudi, 1844) in two localities of the Cerrado and FN=52 in one locality in the Cerrado and the Amazon. All taxa with 2n=44 have a medium-sized acrocentric X chromosome and a small Y.Rhipidomys nitela is different from the species with 2n=44 by presenting a heterochromatic short arm of the X chromosome. In all karyotypes analysed, the nucleolus organizer regions were located in the short arms of two to six pairs and the (T₂AG₃)_n telomeric probes hybridizedin situ in both the short and long arms of all pairs of the karyotypes.     

Description of the karyotype of Rhagomys rufescens Thomas, 1886 (Rodentia, Sigmodontinae) from Southern Brazil Atlantic forest

Rhagomys rufescens (Rodentia: Sigmodontinae) is an endemic species of the Atlantic forest from Southern and Southeastern Brazil. Some authors consider Rhagomys as part of the tribe Thomasomyini; but its phylogenetic relationships remain unclear. Chromosomal studies on eight specimens of Rhagomys rufescens revealed a diploid number of 2n = 36 and a number of autosome arms FN = 50. GTG, CBG and Ag-NOR banding and CMA(3) /DAPI staining were performed on metaphase chromosomes. Eight biarmed and nine acrocentric pairs were found in the karyotype of this species. The X and Y chromosomes were both acrocentric. Most of the autosomes and the sex chromosomes showed positive C-bands in the pericentromeric region. The X chromosome showed an additional heterochromatic block in the proximal region of the long arm. Nucleolus organizer regions (NORs) were located in the pericentromeric region of three biarmed autosomes (pairs 4, 6 and 8) and in the telomeric region of the short arm of three acrocentrics (pairs 10, 12 and 17). CMA (3) /DAPI staining produced fluorescent signals in many autosomes, especially in pairs 4, 6, and 8. This study presents cytogenetic data of Rhagomys rufescens for the first time.     

Cytogenetic analysis of some Brazilian marsupials (Didelphidae: Marsupialia)

Three species of marsupials from the Amazon region (Marmosa cinerea, Caluromys lanatus, and Didelphis marsupialis) and two from the region of S?o Paulo (Didelphis marsupialis and Didelphis albiventris) were studied. The G-banding pattern of the species with 2n = 14 (M. cinerea and C. lanatus) was very similar, as well as the pattern of G-bands in the species with 22 chromosomes (Didelphis). All of the autosomes of M. cinerea and D. albiventris have centromeric C-bands and the Y chromosome is totally C-band positive. The long arm of the M. cinerea X chromosome is completely C-band positive except for a negative band close to the centromeric region. In D. albiventris the long arm of the X chromosome is C-band positive except for a negative band close to the telomeric region. In M. cinerea the silver-stained nucleolar organizer regions (Ag-NORs) are found in the acrocentric chromosomes, being located in the telomeric region of one pair and in the centromeric region of the other pair. Caluromys lanatus has centromeric Ag-NORs in one acrocentric and in one submetacentric chromosome pairs. Didelphis marsupialis has three chromosome pairs with telomeric Ag-NORs. In D. albiventris the Ag-NORs are terminal and located in both arms of one pair and in the long arm of two pairs of chromosomes.     

A new chromosomal race (2n=44) of Nannospalax xanthodon from Turkey (Mammalia: Rodentia)

A new karyotype for blind mole rats was recorded in Tunceli province in Eastern Turkey. The karyotype contained 44 chromosomes, including 13 biarmed pairs, 7 acrocentric pairs, and one heteromorphic pair with a submetacentric and an acrocentric homologue in the autosomal complement (FNa=69). The X chromosome was submetacentric and the Y chromosome medium-sized subtelocentric (FN=73). Distinct dark centromeric C-bands were observed on most of the biarmed and three pairs of the acrocentric autosomes. The NORs were detected on short arms of three subtelocentric pairs and one acrocentric pair of autosomes. The diploid number of chromosomes and the karyotype characteristics observed are obviously unique among hitherto studied populations of blind mole rats and the complement can be evaluated as a new chromosome race of Nannospalax xanthodon. The distribution ranges of individual chromosome races of the species recorded in Eastern Anatolia are revised and possible interracial hybridization is discussed in respect of the finding of a new race.     

A satellited Y chromosome]

A previous report in 1967 on the observation of a satellited Y chromosome found in a French Canadian family line is confirmed by the use of the ammoniacal silver procedure which stains selectively the nucleolus organizer regions (NORs) in acrocentric human chromosomes. There is evidence that this peculiar chromosome results from the translocation to the distal end of the Y chromosome long arms of a satellited segment from a D or G autosome.     

Heterochromatin, synaptonemal complex, and NOR activity in the somatic and germ cells of a male domestic dog, Canis familiaris (Mammalia, Canidae)

C-banding and silver staining of the somatic and germ cells of the male domestic dog. Canis familiaris, have shown that: (1) the amount of C-banding is small compared to most other mammalian species, (2) three pairs of autosomes have nucleolus organizer regions (NORs) at the terminal ends of their long arms, whereas the Y chromosome has an NOR on the terminal end of the short arm, (3) the organization of the synaptonemal complex (SC) is similar to that of other mammalian species, (4) a distinct SC is formed between the long arm of the Y chromosome and probably the short arm of the X chromosome, and (5) the differential axes of both sex chromosomes do not demonstrate fusiform thickenings nor do they stain darkly with silver as do the XY bivalents in many other mammalian species.     

Detection of nucleolus organizer regions in chromosomes of human,chimpanzee, gorilla,orangutan and gibbon

Nucleolus organizer regions were detected by the Ag-AS silver method in fixed metaphase chromosomes from human and primates. In the human, silver was deposited in the secondary constriction of a maximum of five pairs of acrocentric chromosomes: 13, 14, 15, 21 and 22. The chimpanzee also had five pairs of acrocentric chromosomes stained, corresponding to human numbers 13, 14, 18, 21 and 22. A gibbon had a single pair of chromosomes with a secondary constriction, which corresponded to the nucleolus organizer region. In each case the Ag-AS method detected the sites which have been shown by in situ hybridization to contain the ribosomal RNA genes. An orangutan had eight pairs of acrocentric chromosomes stained with Ag-AS, probably corresponding to human numbers 13, 14, 15, 18, 21 and 22, plus two others. Two gorillas had silver stain over two pairs of small acrocentric chromosomes and at the telomere of one chromosome 1. The larger gorilla acrocentric chromosomes had no silver stain although they all had secondary constrictions and entered into satellite associations.     

Karyotype and heterochromatin pattern of the field mouse,Apodemus argenteus Temminck

The field mouse,Apodemus argenteus Temminck, has 46 chromosomes. The autosomes comprise 20 pairs of acrocentrics and 2 pairs of metacentrics. The X chromosome is represented by an outstandingly large submetacentric element, while the Y is an acrocentric corresponding in size to the 5th or 6th pair of autosomes. All of the autosomes and gonosomes can be unequivocally identified by their characteristic Q-band or G-band patterns. The constitutive heterochromatin, as revealed by C-banding, is localized at the centromeric regions of all autosomes, the short arm and the proximal 1/3 of the long arm of the X chromosome, and the entire Y chromosome. The C-band-positive segments which constitute 33.5% of the genome exhibit dark fluorescence after Q-banding, late DNA replication, faint or positive staining reaction to G-banding, fast reassociation of DNA revealed by AO staining, and allocyclic behavior of the sex-bivalent in male meiosis. An exception to the above is the distal segment of the Y which is positive to both C- and Q-banding. The giant X chromosome occupies 13.1% of the genome, leaving 5.6% of euchromatic segments, the latter value being equivalent to that of the original type X.     

Karyotypes of two rare rodents, Hapalomys delacouri and Typhlomys cinereus (Mammalia, Rodentia), from Vietnam

Karyotypes of Hapalomys delacouri (Rodentia, Muridae) and Typhlomys cinereus (Rodentia, Platacanthomyidae) from Vietnam are described for the first time. The diploid karyotype of Hapalomys delacouri is 38 (NFa=48), consisting of six pairs of bi-armed and 12 pairs of acrocentric autosomes decreasing in size; plus a large metacentric X chromosome and Y chromosome, also metacentric, that is equal in size to the largest pair of acrocentric autosomes. The newly described karyotype differs significantly from that reported for Hapalomys delacouri from northern Thailand. The latter record very likely represents a different species of Hapalomys, possibly the taxon Hapalomys pasquieri described from north-central Laos.The diploid karyotype of Typhlomys cinereus is 38 (NF=48), consisting of five pairs of meta- to submetacentric and 14 pairs of acrocentric chromosomes varying in size from large to small; sex chromosomes were not defined.     

Nucleolus organizer regions of the canine karyotype

Silver-stained preparations of cultured lymphocytes obtained from 12 pure-bred dogs revealed the presence of nucleolus organizer regions (NORs) on four to seven chromosomes in females and five to eight chromosomes in males. All seven males had a NOR on the Y chromosome. The telomeric location of the NORs on the autosomes suggested by an earlier study was confirmed.     

Karyotypes and systematics of Asian high-mountain voles, genus Alticola (Rodentia, Arvicolidae). Results of Mongolian-German biological expeditions since 1962, No. 211.

Six species/subspecies of Asian high-mountain voles, genus Alticola, were studied cytogenetically via conventional staining and C- and G-banding. The karyotypes are very similar. The standard karyotype, as in A. strelzovi strelzovi, consists of 56 chromosomes. These are split into 25 acrocentric pairs, one large subtelocentric pair, one small metacentric pair, a large acrocentric X chromosome, and a small Y chromosome, which varies in shape. Constitutive heterochromatin is almost entirely restricted to small centromeric regions. A small submetacentric pair of autosomes in both subspecies of A. semicanus and a medium-sized Y chromosome in A. argentatus severtzovi are of importance in systematics. The data suggest that A. barakshin, A. semicanus, and A. argentatus are separate species.     

Karyotype and divergence of stream Dolly Varden from the Southern Sakhalin

The karyotype of stream Dolly Varden inhabiting a tributary of the Belaya River (the basin of Naiba River, southern Sakhalin) was determined (2n = 82 and NF = 98 + 2). According to the main characteristics (chromosome number and arm number, the presence of a pair of marker submeta-subtelocentric chromosomes with nucleolus organizer regions (NORs), one pair of large acrocentric chromosomes, and one pair of subtelocentric chromosomes), this karyotype is identical to the karyotype of anadromous southern Dolly Varden from Salvelinus malma krasheninnikovi of Primorye and Japan. However, in most stream Dolly Varden individuals, additional active nucleolus organizer regions (NORs) located in telomeric and paracentric regions of two to three pairs of acrocentric chromosomes were revealed. It is suggested that the stream and anadromous southern forms of Dolly Varden are evolutionarily related NORs that are silent in the anadromous souther form are active in the stream form. Possible causes of these differences in NOR activity are discussed.     

The Location of the nucleolus organizer regions in Drosophila hydei

The positions of the nucleolus organizer regions in metaphase chromosomes of Drosophila hydei were detected by in situ hybridization experiments. In agreement with earlier conclusions the nucleolus of the X chromosome was found to originate in a terminal region of the heterochromatic arm. The Y chromosome contains two nucleolus organizers, one in a terminal position of the long arm, and the other in the short arm. The implications with respect to the evolution of the Y chromosome are discussed.     

Chromosomal description of the rodent generaOecomys andNectomys from Brazil

We analysed karyotypes of five taxa of the rodent generaOecomys andNectomys, trapped in 14 localities in an area ranging from 8° to 29°S on Brazilian territory.Oecomys cf.concolor, collected in the Amazon and in two localities of the Cerrado biome, showed a 2n=60 karyotype constituted by a pair of large subtelocentric chromosomes, a small metacentric pair and 27 acrocentric pairs. The X chromosome was a large submetacentric and a subtelo-submetacentric, the morphology of the latter showing variable C-banding patterns. In all three localities the Y chromosome was a medium size heterochromatic acrocentric. Two individuals from the Cerrado had a heterochromatic acrocentric B-chromosome.Oecomys cf.bicolor presented two cytotypes, 2n=80 in the specimens from the Cerrado biome and 2n=82 in individuals trapped in the Amazon. The 2n=80 cytotype 1 showed a large subtelocentric, 22 biarmed pairs (medium to small) and 16 acrocentric autosomal pairs. The karyotype of the 2n=82 cytotype 2 is constituted by 15 biarmed chromosomes (median to small) and 25 acrocentric pairs with heterochromatic blocks at pericentromeric regions. The sexual pairs were the same (large submetacentric X and median acrocentric Y) in both cytotypes. InO. cf.concolor and in both cytotypes ofO. cf.bicolor the nucleolar organizer regions were observed in 1-3 pairs, located in the short arms.Nectomys genus presented two cytotypes, 2n=52–55 (N. rattus, with 0–3 biarmed heterochromatic accessory chromosomes) and 2n=56–59 (N. squamipes, bearing 0–3 biarmed, heterochromatic, B-chromosomes). These 2 cytotypes occupy disjunct regions of South America, with overlapping areas in the Brazilian states of Pernambuco, Bahia, and Mato Grosso do Sul.     

Karyotypic variation in two species of jerboas Jaculus jaculus and Jaculus orientalis (Rodentia, Dipodidae) from Tunisia

The karyotypes of the lesser Egyptian jerboa Jaculus jaculus and the greater Egyptian jerboa Jaculus orientalis from Tunisia are described and compared with available data particularly from Egypt. The species examined have a similar karyotype consisting of 2n = 48 chromosomes and a fundamental number of autosomes (NFa) varying from 88 to 90 in J. jaculus and from 84 to 88 in J. orientalis. The X chromosome is submetacentric in both species, while the Y is submetacentric in J. orientalis and acrocentric in J. jaculus. Most of the autosomes are meta/submetacentric but the small pairs 22 - 23 in J. jaculus and 20-23 in J. orientalis are frequently acrocentric, yielding considerable differences in the NFa within and among species. Morphological variation in these small pairs of autosomes and/or in the Y chromosome in J. orientalis may distinguish populations of the two species from Egypt and Tunisia. The differences observed either between Egypt and Tunisia or between the Tunisian Jaculus species are probably associated with chromosomal rearrangements such as pericentric inversions or heterochromatin variation. They appear of lesser magnitude than other changes (especially molecular) that have occurred during the evolution of this genus.