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.
Highlights
Fishes of the family Loricariidae are found in almost all South and Central America, from Costa Rica to Argentina and represent one of the world’s largest fish families, with about 690 species described and about 300 undescribed (Reis et al 2003)
Cytogenetic analyses were performed on chromosome preparations obtained from four species collected in rivers from Brazil and Venezuela: Kronichthys lacerta (Nichols 1919), Pareiorhaphis splendens (Bizerril 1995), Liposarcus multiradiatus (Hancock 1828) and Hypostomus prope plecostomus (Linnaeus 1758) (Table 1)
The results showed that Kronichthys lacerta had only one signal of 18S rDNA in interstitial position in the long arm of the chromosome pair 21 (Figure 1a), coinciding with a single Ag-NORs pattern presented by Alves et al (2005)
Summary
Fishes of the family Loricariidae are found in almost all South and Central America, from Costa Rica to Argentina and represent one of the world’s largest fish families, with about 690 species described and about 300 undescribed (Reis et al 2003). The 18S rDNA gene probes by fluorescent in situ hybridization (FISH) have provided coincident markers with silver nitrate impregnation (AG-NOR) in nucleolar organizer region (Ag-NOR) in fish chromosomes (Paintner et al 2002, Porto-Foresti et al 2002, Fontana et al 2003, Kavalco et al 2005). Ag-NORs size polymorphism is common in Loricariidae fishes, mainly in species with single Ag-NORs as in Hypoptopomatinae and Neoplecostominae, it can occur in species with multiple Ag-NORs as Hypostominae (Artoni and Bertollo 1996, Alves et al 2003).
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