Cytogenetic Characterization of Geophagus brasiliensis and Two Species of Gymnogeophagus (Cichlidae: Geophaginae) from Guaíba Lake, RS, Brazil

Abstract

The karyotypes of three species of fish of the Cichlidae family from the Forqueta river and several locations in Guaíba lake/RS (Brazil) were analyzed. All species presented 2n=48, while Gymnogeophagus gymnogenys showed two karyotypic formulae: 4m+44st-a with FN=52 and 6m+42st-a with FN=54. Gymnogeophagus labiatus presented 4m+4sm+40st-a and FN=56 and Geophagus brasiliensis 4sm+44st-a and FN=52. Simple NORs were found in all species with the exception of a population of G. gymnogenys from Saco da Alemoa/Barra do Ribeiro. CMA ! staining revealed NOR sites, while DAPI staining was negative and heterochromatin was limited to pericentromeric regions and associated to NORs, except in G. labiatus. The data show a conserved pattern in Geophagus brasiliensis and karyotype variation in the species of Gymnogeophagus.

Cytogenetics of Gymnogeophagus setequedas (Cichlidae: Geophaginae), with comments on its geographical distribution

“…In G. gymnogenys, by contrast, the NORs are found in an interstitial position on the long arm of the subtelo-acrocentric chromosome pair 3 and a terminal position on the short arm of the subtelo-acrocentric pair 9 (Pires et al, 2010). By contrast, simple NORs were observed in an interstitial position on the short arm of the metasubmetacentric chromosome pair in G. balzanii (Roncati et al, 2007), G. labiatus (Pires et al, 2010) and B. cupido , and in a terminal position on the short arm of the subtelo-acrocentric chromosome in Geophagus brasiliensis (Vicari et al, 2006) and Satanoperca jurupari (Poletto et al, 2010a). The presence of simple NORs in the first chromosome pair (meta-submetacentric) is probably a plesiomorphic condition in Neotropical cichlids (Feldberg, Bertollo, 1985b).…”

“…3). The presence of heterochromatin in the centromeric and pericentromeric regions of most of the chromosomes of the complement has also been observed in Gymnogeophagus gymnogenys, Geophagus brasiliensis (Pires et al, 2010), Biotodoma cupido and Geophagus proximus (Geophagini), Cichla monoculus (Schneider et al, 2013) (Cichlini), Cichlasoma facetum (probably Australoheros tavaresi Ottoni, 2012) (Vicari et al, 2006), and the heroin, A. angiru (Paiz et al, 2014) (Heroini). This is a common pattern in Neotropical cichlids (Feldberg et al, 2003;Valente et al, 2012).…”

“…Silver nitrate impregnation revealed multiple NORs in G. setequedas, a pattern also found in one population of G. gymnogenys (Pires et al, 2010), but with considerable differences in the NORs distribution. In G. setequedas, the NORs are present in a terminal position on the long arm of the subtelo-acrocentric pair 8 and in one acrocentric chromosome of pair 20.…”

“…The diploid number of 48 chromosomes found in Gymnogeophagus setequedas is the same as the number observed in congeneric species. However, the karyotype formula for G. setequedas (4sm + 24st + 20a) differs from those of its congeners, such as G. balzanii (2m-sm + 46st-a, Roncati et al, 2007), G. gymnogenys (4m + 44st-a; 6m + 42st-a), and G. labiatus (4m + 4sm + 40st-a) (Pires et al, 2010). These differences may reflect structural rearrangements, such as inversions and/or translocations, or may be due to the condensation or reorganization of the chromosomes, as proposed by the respective authors.…”

“…Previous cytogenetic data are available for species of the genera Geophagus Heckel, 1840 (Vicari et al, 2006;Pires et al, 2010;Nakajima et al, 2012;Schneider et al, 2013;Perazzo et al, 2013), Gymnogeophagus Miranda Ribeiro, 1918 (Pires et al, 2010), Apistogramma Regan, 1913, Biotodoma Eigenmann & Kennedy, 1903and Satanoperca Günther, 1862(Poletto et al, 2010a. In the case of Gymnogeophagus, cytogenetic studies have focused on just three species, G. balzanii (Feldberg, Bertollo, 1984, 1985aRoncati et al, 2007), G. gymnogenys and G. labiatus (Pires et al, 2010). These species have a diploid number of 48 chromosomes, a centromeric/pericentromeric distribution of heterochromatin, and simple nucleolar organizer regions (NORs), located predominantly on the first chromosome pair.…”