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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.

Characterization of invasive fish species in a river transposition region: evolutionary chromosome studies in the genus Hoplias (Characiformes, Erythrinidae)

“…2). In all the karyomorphs of the H. malabaricus complex, heterochromatin is generally located in the pericentromeric and terminal region of some chromosome pairs (Dergam and Bertollo 1990;Haaf et al 1993;Bertollo et al 1997a, b;Born and Bertollo 2000;Vicari et al 2005), which was corroborated in the present study. However, in the specimens from the H. lacerdae group, heterochromatin was found in the pericentromeric region in most of the chromosomes, with only one pair exhibiting terminal staining, which can therefore be considered an useful marker for distinction between the H. malabaricus and H. lacerdae groups (Fig.…”

The key role of repeated DNAs in sex chromosome evolution in two fish species with ZW sex chromosome system

“…For example, the Neotropical fish Hoplias malabaricus has different sex chromosome systems, as well as distinct evolutionary stages of sex chromosome differentiation found among its populations. In some populations of this species, a well-differentiated XX/XY sex chromosome system can be found in which the X chromosome clearly differs from the Y by the accumulation of DNA repeats [30,31]. At least 15 distinct repetitive DNA classes (including satellites, TEs, and microsatellites repeats) accumulated in the heterochromatic region of the X chromosome.…”

Karyotypic conservatism in five species of Prochilodus (Characiformes, Prochilodontidae) disclosed by cytogenetic markers

“…In addition to P. lineatus (Jesus and Moreira-Filho, 2003; Vicari et al , 2006; Voltolin et al , 2009), this synteny was also observed in Salmo salar (Pendás et al , 1994), Oncorhynchus mykiss (Móran et al , 1996), Astyanax (Almeida-Toledo et al , 2002), in amphibians (Lucchini et al , 1993) and, more recently, in Pimelodus britskii (Moraes-Neto et al , 2011). On the other hand, these loci have been mapped on different chromosomes in many fish species (Martinez et al , 1996; Morán et al , 1996; Born and Bertollo , 2000 ; Ferro et al , 2001; Vicente et al , 2001; Wasko et al , 2001; Noleto et al , 2007), representing the most frequent condition in vertebrates (Lucchini et al , 1993; Drouin and Muniz De Sá, 1995, Suzuki et al , 1996). …”