Mapping of ribosomal genes and chromosomal markers in three species of the genus Serrasalmus (Characidae, Serrasalminae) from the Amazon basin

Abstract

Karyotypic characteristics of three species of the genus serrasalmus (S. altispinnis, S. gouldingi and S. Serrulatus) from the middle and lower Negro River, Amazon Basin, were investigated using different staining techniques and Fluorescent in situ hybridization with 5S and 18S rDNA probes. The diploid number was invariably 2n = 60 and the fundamental number was FN = 110. Nevertheless, the karyotypes differed from each other in composition: 24m, 20sm, 6st, 10a in S. altispinnis; 22m, 22sm, 6st, 10a in S. gouldingi and 20m, 22sm, 8st, 10a in S. serrulatus. The karyotype of S. altispinnis differed from the one previously described in a population from the Pitinga River. C-positive constitutive heterochromatin was mainly pericentromeric in the karyotypes of all species. Nucleolar organizer regions were multiple and preferentially located terminally on the short arms of the subtelocentric/acrocentric chromosomes, as evidenced by both silver nitrate staining and fluorescent in situ hybridization with the 18S rDNA probe. The maximum number of NORs varied among species, as did the NOR-bearing chromosomes. FISH with the 5S rDNA probe produced an interstitial signal on the long arms of the pair 7 in all species, coincident with a C-positive heterochromatic band. While some chromosome features were shared by the three species, some were species-specific and thus useful for cytotaxonomy.

Comparative Cytogenetic Analysis of the Genus <i>Symphysodon</i> (Discus Fishes, Cichlidae): Chromosomal Characteristics of Retrotransposons and Minor Ribosomal DNA

“…Regarding the physical chromosomal location of the repetitive 5S rRNA genes, the mapping of these sequences in different fish species has revealed that these sites are commonly located on only one pair of chromosomes and in the interstitial segments of the chromosomes [reviewed by Martins and Wasko, 2004;Ferreira et al , 2007;Nakayama et al , 2008]. This same pattern has also been observed for mammals [Frederiksen et al , 1997] as well as amphibians [Schmid et al , 1987;Lucchini et al , 1993].…”

Karyotype differentiation and cytotaxonomic considerations in species of Serrasalmidae (Characiformes) from the Amazon basin

“…Previous data on another three species of Serrasalmus [S. altispinnis, S. gouldingi, and S. serrulatus (Nakayama et al, 2008)] were also included in this table to provide a comparative analysis.…”

“…Ag-NORs in Serrasalmidae have been analyzed since the 1980s and have invariably been visualized as multiple sites usually located in the terminal region on the short arms of subtelo-acrocentric chromosomes, although some species bear terminal Ag-NORs on the long arms (Galetti Jr. et al, 1985;Almeida-Toledo et al, 1987;Cestari & Galetti Jr. 1992a, b;Martins-Santos et al, 1994;Nakayama et al, 2001Nakayama et al, , 20022008;Centofante et al, 2002a;Nirchio et al, 2003;Gaviria et al, 2005). However, the numerical variation in these regions (in both inter and intra-specific terms) is much more notable than the positional differences, ranging from four sites in C. macropomum to 12 sites in S. rhombeus (Table 1).…”

“…However, full correspondence between 18S rDNA and Ag-NOR sites was not constantly observed, since in some species, the number of 18S rDNA sites was greater than the number of Ag-NORs. Moreover, the location of some 18S rDNA sites was not detected by silver nitrate in S. rhombeus and S. serrulatus (Nakayama et al, 2008) (Table 1). Two probable reasons may putatively explain these divergences.…”

Stable karyotypes: a general rule for the fish of the family Prochilodontidae?

“…The physical chromosome mapping of the 5S rDNA sequences in various fish species indicated that these sites were generally located in the interstitial segments of the chromosomes (see reviews by Martins & Wasko, 2004;Ferreira et al, 2007;Nakayama et al, 2008) and this same pattern has likewise been observed in mammals (Frederiksen et al, 1997) and in amphibians (Schmid et al, 1987;Lucchini et al, 1993). This pattern of interstitial chromosome localization in a single chromosome pair appears to correspond to an ancestral condition that has been maintained in most groups.…”