The idiogram of the Venezuelan vole mouse, &lt;i&gt;Akodon urichi venezuelensis&lt;/i&gt; Allen (Rodentia, Cricetidae)

Reig, Osvaldo A.; Olivo, Nelly; Kiblisky, P.

doi:10.1159/000130132

Cited by 19 publications

(8 citation statements)

References 10 publications

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“…Among the South American cricetids whose X chromosomes have been measured, with the exception of the monotypical genus Reithrodon (Freitaset al, 1983), the only species that show an increase in length of this chromosome are akodonts: A urichi venezuelensis (10.07%. Reig et al, 1971); A varius simulator (8.8%), A boliviensis tucumanensis (8.9%, and A b spegazzini (8.8%), studied by Bianchi et al (1971). Thus, while the absence of the marker chromosome seems to exclude Deltamys as a subgenus of Akodon, the size of its X chromosome indicates that it should fall within the akodont group, supporting the taxonomic point of view (Massoia.…”

Section: Discussionmentioning

confidence: 96%

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

Sbalqueiro

Mattevi

Oliveira

1984

Cytogenet Genome Res

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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/X₁X₂Ythis 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 X₁and 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 X₁chromosome 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.

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Section: Discussionmentioning

confidence: 96%

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

Sbalqueiro

Mattevi

Oliveira

1984

Cytogenet Genome Res

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“…Chromosomal spreads from bone marrow were prepared following Reig et al (1971) and stained with Giemsa. Chromosomes were classified according to Levan et al (1964).…”

Section: Methodsmentioning

confidence: 99%

New Ctenomys karyotypes (Rodentia, Octodontidae) from north-eastern Argentina and from Paraguay confirm the extreme chromosomal multiformity of the genus

1990

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Bone-marrow karyotypes of 68 specimens of the subterranean octodontid rodent genus Ctenomys from 16 different populations of north east Argentina and one from Paraguay have been studied. A surprising variety of chromosome numbers was found, ranging from 2n:42 to 2n=70. Some of the karyomorphs are clearly assigned to named species by topotypy: C. conoveris 2n=50, FN=56; C. argentinus, 2n=44, FN=54; C. perrensi, 2n=50, FN:84; C. dorbignyi, 2n:70, FN:84; C. roigi, 2n:48, FN=80; C. yolandae, 2n:50, FN=78. Four populations of Corrientes Province similar in morphology to C. perrensi were found to be polymorphic and polytypic; they maintain the same FN:84, but diploid numbers increase from 2n--54 to 2n:58 from SW to the NE, thus suggesting Robertsonian rearrangements. In the middle of this cline, a stable karyomorph of2n:62, FN:84 was found in two different populations, suggesting to belong to an undescribed species. Another karyomorph of 2n:42, FN=76 found in Curuzfi Laurel, Corrientes, may also prove to represent another undescribed species. One karyomorph of 2n=52, FN:74, and another of 2n---56, FN=78 from Paranfi and Ubajay (Entre Rios Province, Argentina) respectively are close to C. rionegrensis. The relationships among these karyomorphs is considered in light of data on sperm morphology. The hypothesis is advanced that karyotypic rearrangements among the FN=84 group may be the result of Robertsonian repatterning from a 2n:70 original widespread form. Fixation of chromosomal variants is correlated with patchy distribution and small size of unstable demes, and may or may not have resulted in reproductive isolation.

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“…The karyology of the genus Akodon has been extensively analysed by several authors (Bianchi & Contreras, 1967;Bianchi et al, 1968Bianchi et al, , 1969Bianchi et al, , 1971Bianchi et al, , 1976Oliveira et al, 1979;Merani et aL, 1978Merani et aL, , 1980Reig et al, 1971;Fronza et al, 1979;Kibliski et al, 1976;Yonenaga, 1972). Thus far, more than half of the species in the genus have been cytogeneticaly studied and the presence of inter-and intraspecies chromosomal polymorphisms has been reported in many cases.…”

Section: Introductionmentioning

confidence: 99%

Cytogenetics of the South American Akodont rodents (Cricetidae) X. Akodon mollis: a species with XY females and B chromosomes

et al. 1982

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The morphology, G-and C-banding pattern of the Akodon mollis chromosome complement is analysed. Over a total of 14 males and 10 females studied, 8 males and 7 females had a modal chromosome number of 22, while 6 males and 3 females showed a modal number of 23 chromosomes. In the animals with 23 chromosomes the odd element was considered a B chromosome on the basis of: (a) its small size, (b) the lack of an homologous chromosome and the subsequent formation of univalents at diakinesis and metaphase I from testes, (c) the weak or null genetic action as evidenced by the lack of any obvious variation in the phenotype of carriers.Four females exhibited a sex-pair dimorphism indistinguishable from that observed in males, The G-banding analysis showed homology between the pattern found in the Y chromosome and that detected in the short arm of the X. The ~tudy of C-band distribution showed that several autosome pairs and the X chromosomes had small masses of centromeric heterochromatin. On the other hand, the Y and B chromosomes were C-band negative. The Y-like chromosome in females with dimorphism of the sex pair was also C-band negative. Accordingly these females were considered to be XY and not Xx (the x being an extensively deleted X chromosome).

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The idiogram of the Venezuelan vole mouse, <i>Akodon urichi venezuelensis</i> Allen (Rodentia, Cricetidae)

Cited by 19 publications

References 10 publications

An X<sub>1</sub>X<sub>1</sub>X<sub>2</sub>X<sub>2</sub>/X<sub>1</sub>X<sub>2</sub>Y mechanism of sex determination in a South American rodent, <i>Deltamys kempi</i> (Rodentia, Cricetidae)

An X<sub>1</sub>X<sub>1</sub>X<sub>2</sub>X<sub>2</sub>/X<sub>1</sub>X<sub>2</sub>Y mechanism of sex determination in a South American rodent, <i>Deltamys kempi</i> (Rodentia, Cricetidae)

New Ctenomys karyotypes (Rodentia, Octodontidae) from north-eastern Argentina and from Paraguay confirm the extreme chromosomal multiformity of the genus

Cytogenetics of the South American Akodont rodents (Cricetidae) X. Akodon mollis: a species with XY females and B chromosomes

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