Localization of 18S ribosomal genes in suckermouth armoured catfishes Loricariidae (Teleostei, Siluriformes) with discussion on the Ag-NOR evolution

Abstract

The family Loricariidae with about 690 species divided into six subfamilies, is one of the world's largest fish families. Cytogenetic studies conducted in the family showed that among 90 species analyzed the diploid number ranges from 2n=38 in Ancistrus sp. to 2n=96 in Hemipsilichthys gobio Luetken, 1874. In the present study, fluorescence in situ hybridization (FISH) was employed to determine the chromosomal localization of the 18S rDNA gene in four suckermouth armoured catfishes: Kronichthys lacerta (Nichols, 1919), Pareiorhaphis splendens (Bizerril, 1995), Liposarcus multiradiatus (Hancock, 1828) and Hypostomus prope plecostomus (Linnaeus, 1758). All species analyzed showed one chromosome pair with 18S rDNA sequences, as observed in the previous Ag-NORs analyses. The presence of size and numerical polymorphism was observed and discussed, with proposing a hypothesis of the Ag-NOR evolution in Loricariidae.

Physical Mapping of the 5S and 18S rDNA in Ten Species ofHypostomusLacépède 1803 (Siluriformes: Loricariidae): Evolutionary Tendencies in the Genus

“…Artoni and Bertollo [ 28 ] also consider single NORs as the ancestral phenotype for Loricariidae. These characteristics observed on basal genera for Loricariidae, besides other tribes of Hypostominae such as Pterygoplichthini and Ancistrini [ 23 , 29 ], support the hypothesis that the presence of one site of 5S and 18S rDNAs is basal for Hypostomus .…”

Cytogenetic analysis of two locariid species (Teleostei, Siluriformes) from Iguatemi River (Parana River drainage) in Brazil

“…Others species previously analyzed of tribe Pterygoplichthini as Pterygoplichthys joselimaianus (Oliveira et al 2006), Pterygoplichthys anisitsi (Artoni et al 1999, Alves et al 2006), Pterygoplichthys multiradiatus (Alves et al 2006; Alves et al 2012) and Pterygoplichthys gibbiceps (Alves et al 2006) also present this same pattern, with subterminal markings, but with differences in location (long or short arm) and type of NOR-bearing chromosome. According to Oliveira and Gosztonyi (2000) the condition of single Ag-NORs in subterminal location is the possible basal condition for the Siluriformes.…”

Studies in two allopatric populations of Hypostomus affinis (Steindachner, 1877): the role of mapping the ribosomal genes to understand the chromosome evolution of the group

“…However, other factors should be considered in the chromosome evolution of the group, such as the dispersion trends of repetitive sequences such as ribosomal genes (Kavalco et al 2004a). Because the presence of a pair of chromosomes carrying the rDNA in fish is thought to be a plesiomorphic condition (Martins and Galetti Jr 1999, Oliveira and Gosztonyi 2000), even for Loricariidae (Kavalco et al 2004a, Alves et al 2012), the genus Hypostomus may contain lines with contrasting tendencies (Pansonato-Alves et al 2013) and possibly an ancestral phenotype with a site in a chromosomal pair (Traldi et al 2013). Dispersion of ribosome cistrons may be related to not only species-specific events but also populational events, as in armored catfish in which the formation of isolated populations typically occurs because of low vagility (Artoni and Bertollo 2001, Bitencourt et al 2012).…”