Gene mapping of 5S rDNA sites in eight fish species from the Paraíba do Sul river basin, Brazil

Abstract

The use of improved cytogenetic techniques such as fluorescent in situ hybridization (FISH) has offered important methodologies for cytotaxonomic and evolutionary studies. In particular, the mapping of 5S rDNA sites has proved to be an excellent marker in the study of different organisms and, more recently, in fish. In the present work, the FISH technique was used to map the 5S rDNA sites in the chromosomes of eight neotropical fish species from the Paraíba do Sul river basin, four of these belonging to the order Characiformes, family Characidae, genus Astyanax (A. scabripinnis, A. parahybae, A. giton and A. intermedius) and four to the order Siluriformes, family Loricariidae (Neoplecostomus microps, Harttia loricariformis, Hypostomus affinis and Upsilodus sp.). Karyotype evolution aspects of the analyzed groups are discussed.

Physical mapping of the 18S and 5S ribosomal genes in nine Characidae species (Teleostei, Characiformes)

“…However, it is not a diagnostic characteristic for Astyanax, since it extends to species of other unrelated groups such as O. franciscensis, S. heterodon S. piaba and M. micans. Variation in the number and localization of the 5S rDNA loci seems to be common among Astyanax species, ranging from two to eight loci in terminal as well as interstitial positions (Ferro et al, 2001;Kavalco et al, 2004; present study). Yet, the presence of syntenic 18S and 5S rDNA sites in a medium-sized metacentric pair of a few Astyanax species (Almeida-Toledo et al, 2002) does not occur in the Astyanax species here analyzed, since the 18S rDNA sites were not evidenced in any metacentric chromosome of this group.…”

“…It is possible that part of the original 5S rDNA site has been transposed to another chromosome region by a paracentric inversion, as proposed for Upsilodus sp. (Kavalco et al, 2004).…”

Satellite DNA sites in four species of the genus Astyanax (Teleostei, Characiformes)

“…Many of these species inhabit stream headwaters, including highly irregular regions (such as mountain ranges) where the headwaters of the Paraitinga river (Paraíba do Sul river basin, Brazil) are located. Morphological analyses led Weitzman and Malabarba (1998) to propose the genus polyphyly, which was corroborated by the study of 5S rDNA sites distribution (Kavalco et al, 2004a).…”

“…In fish, the hybridization of rDNA probes and of satellite DNAs has provided insights into the relationship among species and their karyotypic diversification (Almeida- Toledo et al, 2002;Ferro et al, 2001;Jesus et al, 2003;Kavalco and Moreira-Filho, 2003;Kavalco et al, 2004a;Kavalco et al, 2005;Martins and Galetti Jr., 1999;Mestriner et al, 2000;Pazza et al, 2005;Vicente et al, 2004).…”

Comparative chromosomal analyses in species of the genus Pimelodella (Siluriformes, Heptapteridae): occurrence of structural and numerical polymorphisms

“…The few data available about the application of this cytogenetic marker in Siluriformes indicate that they present a remarkable variability mainly related to differences in the number of 5S rDNAbearing sites (KAVALCO et al 2004;GARCIA and MOREIRA-FILHO 2008). This feature is not observed in other fi sh orders, commonly characterized by an inter-and intra-generic conservativeness (GALLETI JR. and MARTINS 2004).…”