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  • Hoplias malabaricus  (2)
  • Springer  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Comparative Cytogenetics Among Allopatric Populations of the Fish, Hoplias Malabaricus. Cytotypes with 2n = 42 Chromosomes (2000)
    Springer
    Genetica 110 (2000), S. 1-9 
    Details
    ISSN: 1573-6857
    Keywords: allopatric populations ; Erythrinidae fish ; Hoplias malabaricus ; karyotypic differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The available chromosomal data on Hoplias malabaricus make possible the identification of three major karyotypic forms in this fish group, all of them bearing 2n = 42 chromosomes, and named as Cytotypes A, B and E in previous studies. While Cytotype A and B share a general macrokaryotypic feature, Cytotype E is well differentiated concerning the morphology and size of some chromosome pairs. On the other hand, Cytotype B presents an exclusive XX/XY sex chromosome system. Six allopatric populations, belonging to Cytotype A, were subjected to cytogenetic analysis in the present study. Despite their basic karyotypic similarity, some differences in the chromosome formulae, as well as in the heterochromatin and Ag-NORs locations, were observed among populations indicating that they no more correspond to a unit, at least in the cytogenetical level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017572030350
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  • 2
    Electronic Resource
    Electronic Resource
    An XX/XY Sex Chromosome System in a Fish Species, Hoplias malabaricus, with a Polymorphic NOR-Bearing X Chromosome (2000)
    Springer
    Chromosome research 8 (2000), S. 111-118 
    Details
    ISSN: 1573-6849
    Keywords: Hoplias malabaricus ; polymorphic NOR ; 5S rDNA ; 18S rDNA ; sex chromosomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytogenetic studies were carried out in the fish, Hoplias malabaricus, from the Parque Florestal do Rio Doce (Brazil). This population is characterized by 2n = 42 chromosomes for both males and females and an XX/XY sex chromosome system, confirmed through several banding methods. Females show 24 metacentric, 16 submetacentric and 2 subtelocentric chromosomes. Males show 24 metacentric, 17 submetacentric and 1 subtelocentric chromosomes. While the X chromosome is easily recognized (the only subtelocentric element), the Y chromosome is somewhat difficult to identify but appears to correspond to the smallest submetacentric in the male karyotype. In-situ hybridization with an 18S rDNA probe showed 10 well-labeled chromosomes, including the X chromosome. The 5S rDNA is interstitially located in a single metacentric pair independent of the 18S rDNA sites. The NOR on the X chromosome is always active and occurs adjacent to a heterochromatic distal segment on the long arm. Variations in size of the NORs and/or heterochromatic segment correspond to a polymorphic size condition observed in the X chromosome. The present results confirm the XX/XY sex chromosome system in the population analyzed as well as a new cytotype in the Hoplias malabaricus group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009238402051
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    Paper (German National Licenses)
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